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<h2><span class="refentrytitle"><a name="libvips-header.top_of_page"></a>header</span></h2>
<p>header — get, set and walk image headers</p>
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<a name="libvips-header.stability-level"></a><h2>Stability Level</h2>
Stable, unless otherwise indicated
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<a name="libvips-header.synopsis"></a><h2>Synopsis</h2>
<pre class="synopsis">
#include <vips/vips.h>
#define <a class="link" href="libvips-header.html#VIPS-META-EXIF-NAME:CAPS" title="VIPS_META_EXIF_NAME">VIPS_META_EXIF_NAME</a>
#define <a class="link" href="libvips-header.html#VIPS-META-XMP-NAME:CAPS" title="VIPS_META_XMP_NAME">VIPS_META_XMP_NAME</a>
#define <a class="link" href="libvips-header.html#VIPS-META-IPCT-NAME:CAPS" title="VIPS_META_IPCT_NAME">VIPS_META_IPCT_NAME</a>
#define <a class="link" href="libvips-header.html#VIPS-META-ICC-NAME:CAPS" title="VIPS_META_ICC_NAME">VIPS_META_ICC_NAME</a>
#define <a class="link" href="libvips-header.html#VIPS-META-XML:CAPS" title="VIPS_META_XML">VIPS_META_XML</a>
#define <a class="link" href="libvips-header.html#VIPS-META-RESOLUTION-UNIT:CAPS" title="VIPS_META_RESOLUTION_UNIT">VIPS_META_RESOLUTION_UNIT</a>
#define <a class="link" href="libvips-header.html#VIPS-META-LOADER:CAPS" title="VIPS_META_LOADER">VIPS_META_LOADER</a>
<span class="returnvalue">guint64</span> <a class="link" href="libvips-header.html#vips-format-sizeof" title="vips_format_sizeof ()">vips_format_sizeof</a> (<em class="parameter"><code><a class="link" href="VipsImage.html#VipsBandFormat" title="enum VipsBandFormat"><span class="type">VipsBandFormat</span></a> format</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get-width" title="vips_image_get_width ()">vips_image_get_width</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get-height" title="vips_image_get_height ()">vips_image_get_height</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get-bands" title="vips_image_get_bands ()">vips_image_get_bands</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<a class="link" href="VipsImage.html#VipsBandFormat" title="enum VipsBandFormat"><span class="returnvalue">VipsBandFormat</span></a> <a class="link" href="libvips-header.html#vips-image-get-format" title="vips_image_get_format ()">vips_image_get_format</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<a class="link" href="VipsImage.html#VipsCoding" title="enum VipsCoding"><span class="returnvalue">VipsCoding</span></a> <a class="link" href="libvips-header.html#vips-image-get-coding" title="vips_image_get_coding ()">vips_image_get_coding</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<a class="link" href="VipsImage.html#VipsInterpretation" title="enum VipsInterpretation"><span class="returnvalue">VipsInterpretation</span></a> <a class="link" href="libvips-header.html#vips-image-get-interpretation" title="vips_image_get_interpretation ()">vips_image_get_interpretation</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<a class="link" href="VipsImage.html#VipsInterpretation" title="enum VipsInterpretation"><span class="returnvalue">VipsInterpretation</span></a> <a class="link" href="libvips-header.html#vips-image-guess-interpretation" title="vips_image_guess_interpretation ()">vips_image_guess_interpretation</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<span class="returnvalue">double</span> <a class="link" href="libvips-header.html#vips-image-get-xres" title="vips_image_get_xres ()">vips_image_get_xres</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<span class="returnvalue">double</span> <a class="link" href="libvips-header.html#vips-image-get-yres" title="vips_image_get_yres ()">vips_image_get_yres</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get-xoffset" title="vips_image_get_xoffset ()">vips_image_get_xoffset</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get-yoffset" title="vips_image_get_yoffset ()">vips_image_get_yoffset</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
const <span class="returnvalue">char</span> * <a class="link" href="libvips-header.html#vips-image-get-filename" title="vips_image_get_filename ()">vips_image_get_filename</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
const <span class="returnvalue">char</span> * <a class="link" href="libvips-header.html#vips-image-get-mode" title="vips_image_get_mode ()">vips_image_get_mode</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<span class="returnvalue">double</span> <a class="link" href="libvips-header.html#vips-image-get-scale" title="vips_image_get_scale ()">vips_image_get_scale</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *array</code></em>);
<span class="returnvalue">double</span> <a class="link" href="libvips-header.html#vips-image-get-offset" title="vips_image_get_offset ()">vips_image_get_offset</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *array</code></em>);
<span class="returnvalue">void</span> * <a class="link" href="libvips-header.html#vips-image-get-data" title="vips_image_get_data ()">vips_image_get_data</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
<span class="returnvalue">void</span> <a class="link" href="libvips-header.html#vips-image-init-fields" title="vips_image_init_fields ()">vips_image_init_fields</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code><span class="type">int</span> xsize</code></em>,
<em class="parameter"><code><span class="type">int</span> ysize</code></em>,
<em class="parameter"><code><span class="type">int</span> bands</code></em>,
<em class="parameter"><code><a class="link" href="VipsImage.html#VipsBandFormat" title="enum VipsBandFormat"><span class="type">VipsBandFormat</span></a> format</code></em>,
<em class="parameter"><code><a class="link" href="VipsImage.html#VipsCoding" title="enum VipsCoding"><span class="type">VipsCoding</span></a> coding</code></em>,
<em class="parameter"><code><a class="link" href="VipsImage.html#VipsInterpretation" title="enum VipsInterpretation"><span class="type">VipsInterpretation</span></a> interpretation</code></em>,
<em class="parameter"><code><span class="type">double</span> xres</code></em>,
<em class="parameter"><code><span class="type">double</span> yres</code></em>);
<span class="returnvalue">void</span> <a class="link" href="libvips-header.html#vips-image-set" title="vips_image_set ()">vips_image_set</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">GValue</span> *value</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()">vips_image_get</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">GValue</span> *value_copy</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get-as-string" title="vips_image_get_as_string ()">vips_image_get_as_string</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">char</span> **out</code></em>);
<span class="returnvalue">GType</span> <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()">vips_image_get_typeof</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>);
<span class="returnvalue">gboolean</span> <a class="link" href="libvips-header.html#vips-image-remove" title="vips_image_remove ()">vips_image_remove</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>);
<span class="returnvalue">void</span> * (<a class="link" href="libvips-header.html#VipsImageMapFn" title="VipsImageMapFn ()">*VipsImageMapFn</a>) (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">GValue</span> *value</code></em>,
<em class="parameter"><code><span class="type">void</span> *a</code></em>);
<span class="returnvalue">void</span> * <a class="link" href="libvips-header.html#vips-image-map" title="vips_image_map ()">vips_image_map</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code><a class="link" href="libvips-header.html#VipsImageMapFn" title="VipsImageMapFn ()"><span class="type">VipsImageMapFn</span></a> fn</code></em>,
<em class="parameter"><code><span class="type">void</span> *a</code></em>);
<span class="returnvalue">void</span> <a class="link" href="libvips-header.html#vips-image-set-area" title="vips_image_set_area ()">vips_image_set_area</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">VipsCallbackFn</span> free_fn</code></em>,
<em class="parameter"><code><span class="type">void</span> *data</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get-area" title="vips_image_get_area ()">vips_image_get_area</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">void</span> **data</code></em>);
<span class="returnvalue">void</span> <a class="link" href="libvips-header.html#vips-image-set-blob" title="vips_image_set_blob ()">vips_image_set_blob</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">VipsCallbackFn</span> free_fn</code></em>,
<em class="parameter"><code><span class="type">void</span> *data</code></em>,
<em class="parameter"><code><span class="type">size_t</span> length</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get-blob" title="vips_image_get_blob ()">vips_image_get_blob</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">void</span> **data</code></em>,
<em class="parameter"><code><span class="type">size_t</span> *length</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get-int" title="vips_image_get_int ()">vips_image_get_int</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">int</span> *out</code></em>);
<span class="returnvalue">void</span> <a class="link" href="libvips-header.html#vips-image-set-int" title="vips_image_set_int ()">vips_image_set_int</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">int</span> i</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get-double" title="vips_image_get_double ()">vips_image_get_double</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">double</span> *out</code></em>);
<span class="returnvalue">void</span> <a class="link" href="libvips-header.html#vips-image-set-double" title="vips_image_set_double ()">vips_image_set_double</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">double</span> d</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-get-string" title="vips_image_get_string ()">vips_image_get_string</a> (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code>const <span class="type">char</span> **out</code></em>);
<span class="returnvalue">void</span> <a class="link" href="libvips-header.html#vips-image-set-string" title="vips_image_set_string ()">vips_image_set_string</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *str</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-history-printf" title="vips_image_history_printf ()">vips_image_history_printf</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *format</code></em>,
<em class="parameter"><code>...</code></em>);
<span class="returnvalue">int</span> <a class="link" href="libvips-header.html#vips-image-history-args" title="vips_image_history_args ()">vips_image_history_args</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *name</code></em>,
<em class="parameter"><code><span class="type">int</span> argc</code></em>,
<em class="parameter"><code><span class="type">char</span> *argv[]</code></em>);
const <span class="returnvalue">char</span> * <a class="link" href="libvips-header.html#vips-image-get-history" title="vips_image_get_history ()">vips_image_get_history</a> (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);
</pre>
</div>
<div class="refsect1">
<a name="libvips-header.description"></a><h2>Description</h2>
<p>
These functions let you get at image header data (including metadata) in a
uniform way. They are handy for language bindings but less useful for C
users.
</p>
<p>
They first search the
VIPS header
fields (see image), then search for
a metadata field of that name (see
meta).
Use <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a> to test for the
existance and <span class="type">GType</span>
of a header field.
</p>
<p>
See meta
for a set of functions for adding new metadata to an image.
</p>
</div>
<div class="refsect1">
<a name="libvips-header.details"></a><h2>Details</h2>
<div class="refsect2">
<a name="VIPS-META-EXIF-NAME:CAPS"></a><h3>VIPS_META_EXIF_NAME</h3>
<pre class="programlisting">#define VIPS_META_EXIF_NAME "exif-data"
</pre>
<p>
The name that JPEG read and write operations use for the image's EXIF data.
</p>
</div>
<hr>
<div class="refsect2">
<a name="VIPS-META-XMP-NAME:CAPS"></a><h3>VIPS_META_XMP_NAME</h3>
<pre class="programlisting">#define VIPS_META_XMP_NAME "xmp-data"
</pre>
<p>
The name that JPEG read and write operations use for the image's XMP data.
</p>
</div>
<hr>
<div class="refsect2">
<a name="VIPS-META-IPCT-NAME:CAPS"></a><h3>VIPS_META_IPCT_NAME</h3>
<pre class="programlisting">#define VIPS_META_IPCT_NAME "ipct-data"
</pre>
<p>
The name that JPEG read and write operations use for the image's IPCT data.
</p>
</div>
<hr>
<div class="refsect2">
<a name="VIPS-META-ICC-NAME:CAPS"></a><h3>VIPS_META_ICC_NAME</h3>
<pre class="programlisting">#define VIPS_META_ICC_NAME "icc-profile-data"
</pre>
<p>
The name we use to attach an ICC profile. The file read and write
operations for TIFF, JPEG, PNG and others use this item of metadata to
attach and save ICC profiles. The profile is updated by the
<a class="link" href="libvips-colour.html#vips-icc-transform" title="vips_icc_transform ()"><code class="function">vips_icc_transform()</code></a> operations.
</p>
</div>
<hr>
<div class="refsect2">
<a name="VIPS-META-XML:CAPS"></a><h3>VIPS_META_XML</h3>
<pre class="programlisting">#define VIPS_META_XML "xml-header"
</pre>
<p>
The original XML that was used to code the metadata after reading a VIPS
format file.
</p>
</div>
<hr>
<div class="refsect2">
<a name="VIPS-META-RESOLUTION-UNIT:CAPS"></a><h3>VIPS_META_RESOLUTION_UNIT</h3>
<pre class="programlisting">#define VIPS_META_RESOLUTION_UNIT "resolution-unit"
</pre>
<p>
The JPEG and TIFF read and write operations use this to record the
file's preferred unit for resolution.
</p>
</div>
<hr>
<div class="refsect2">
<a name="VIPS-META-LOADER:CAPS"></a><h3>VIPS_META_LOADER</h3>
<pre class="programlisting">#define VIPS_META_LOADER "vips-loader"
</pre>
<p>
Record the name of the original loader here. Handy for hinting file formats
and for debugging.
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-format-sizeof"></a><h3>vips_format_sizeof ()</h3>
<pre class="programlisting"><span class="returnvalue">guint64</span> vips_format_sizeof (<em class="parameter"><code><a class="link" href="VipsImage.html#VipsBandFormat" title="enum VipsBandFormat"><span class="type">VipsBandFormat</span></a> format</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-width"></a><h3>vips_image_get_width ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get_width (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-height"></a><h3>vips_image_get_height ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get_height (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-bands"></a><h3>vips_image_get_bands ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get_bands (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-format"></a><h3>vips_image_get_format ()</h3>
<pre class="programlisting"><a class="link" href="VipsImage.html#VipsBandFormat" title="enum VipsBandFormat"><span class="returnvalue">VipsBandFormat</span></a> vips_image_get_format (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-coding"></a><h3>vips_image_get_coding ()</h3>
<pre class="programlisting"><a class="link" href="VipsImage.html#VipsCoding" title="enum VipsCoding"><span class="returnvalue">VipsCoding</span></a> vips_image_get_coding (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-interpretation"></a><h3>vips_image_get_interpretation ()</h3>
<pre class="programlisting"><a class="link" href="VipsImage.html#VipsInterpretation" title="enum VipsInterpretation"><span class="returnvalue">VipsInterpretation</span></a> vips_image_get_interpretation (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-guess-interpretation"></a><h3>vips_image_guess_interpretation ()</h3>
<pre class="programlisting"><a class="link" href="VipsImage.html#VipsInterpretation" title="enum VipsInterpretation"><span class="returnvalue">VipsInterpretation</span></a> vips_image_guess_interpretation (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-xres"></a><h3>vips_image_get_xres ()</h3>
<pre class="programlisting"><span class="returnvalue">double</span> vips_image_get_xres (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-yres"></a><h3>vips_image_get_yres ()</h3>
<pre class="programlisting"><span class="returnvalue">double</span> vips_image_get_yres (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-xoffset"></a><h3>vips_image_get_xoffset ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get_xoffset (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-yoffset"></a><h3>vips_image_get_yoffset ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get_yoffset (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-filename"></a><h3>vips_image_get_filename ()</h3>
<pre class="programlisting">const <span class="returnvalue">char</span> * vips_image_get_filename (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-mode"></a><h3>vips_image_get_mode ()</h3>
<pre class="programlisting">const <span class="returnvalue">char</span> * vips_image_get_mode (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-scale"></a><h3>vips_image_get_scale ()</h3>
<pre class="programlisting"><span class="returnvalue">double</span> vips_image_get_scale (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *array</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-offset"></a><h3>vips_image_get_offset ()</h3>
<pre class="programlisting"><span class="returnvalue">double</span> vips_image_get_offset (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *array</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-data"></a><h3>vips_image_get_data ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> * vips_image_get_data (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
Return a pointer to the image's pixel data, if possible. This can involve
allocating large amounts of memory and performing a long computation. Image
pixels are laid out in band-packed rows.
</p>
<p>
See also: <a class="link" href="VipsImage.html#vips-image-wio-input" title="vips_image_wio_input ()"><code class="function">vips_image_wio_input()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to get data for</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>a pointer to pixel data, if possible.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-init-fields"></a><h3>vips_image_init_fields ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> vips_image_init_fields (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code><span class="type">int</span> xsize</code></em>,
<em class="parameter"><code><span class="type">int</span> ysize</code></em>,
<em class="parameter"><code><span class="type">int</span> bands</code></em>,
<em class="parameter"><code><a class="link" href="VipsImage.html#VipsBandFormat" title="enum VipsBandFormat"><span class="type">VipsBandFormat</span></a> format</code></em>,
<em class="parameter"><code><a class="link" href="VipsImage.html#VipsCoding" title="enum VipsCoding"><span class="type">VipsCoding</span></a> coding</code></em>,
<em class="parameter"><code><a class="link" href="VipsImage.html#VipsInterpretation" title="enum VipsInterpretation"><span class="type">VipsInterpretation</span></a> interpretation</code></em>,
<em class="parameter"><code><span class="type">double</span> xres</code></em>,
<em class="parameter"><code><span class="type">double</span> yres</code></em>);</pre>
<p>
A convenience function to set the header fields after creating an image.
Normally you copy the fields from your input images with
<a class="link" href="libvips-generate.html#vips-image-pipelinev" title="vips_image_pipelinev ()"><code class="function">vips_image_pipelinev()</code></a> and then make
any adjustments you need, but if you are creating an image from scratch,
for example <code class="function">im_black()</code> or <code class="function">im_jpeg2vips()</code>, you do need to set all the
fields yourself.
</p>
<p>
See also: <a class="link" href="libvips-generate.html#vips-image-pipelinev" title="vips_image_pipelinev ()"><code class="function">vips_image_pipelinev()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to init</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>xsize</code></em> :</span></p></td>
<td>image width</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>ysize</code></em> :</span></p></td>
<td>image height</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>bands</code></em> :</span></p></td>
<td>image bands</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>format</code></em> :</span></p></td>
<td>band format</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>coding</code></em> :</span></p></td>
<td>image coding</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>interpretation</code></em> :</span></p></td>
<td>image type</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>xres</code></em> :</span></p></td>
<td>horizontal resolution, pixels per millimetre</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>yres</code></em> :</span></p></td>
<td>vertical resolution, pixels per millimetre</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-set"></a><h3>vips_image_set ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> vips_image_set (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">GValue</span> *value</code></em>);</pre>
<p>
Set a piece of metadata on <em class="parameter"><code>image</code></em>. Any old metadata with that name is
destroyed. The GValue is copied into the image, so you need to unset the
value when you're done with it.
</p>
<p>
For example, to set an integer on an image (though you would use the
convenience function <a class="link" href="libvips-header.html#vips-image-set-int" title="vips_image_set_int ()"><code class="function">vips_image_set_int()</code></a> in practice), you would need:
</p>
<p>
</p>
<div class="informalexample"><pre class="programlisting">
GValue value = { 0 };
g_value_init( &value, G_TYPE_INT );
g_value_set_int( &value, 42 );
vips_image_set( image, field, &value );
g_value_unset( &value );
return( 0 );
</pre></div>
<p>
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()"><code class="function">vips_image_get()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to set the metadata on</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>the name to give the metadata</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>value</code></em> :</span></p></td>
<td>the GValue to copy into the image</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get"></a><h3>vips_image_get ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">GValue</span> *value_copy</code></em>);</pre>
<p>
Fill <em class="parameter"><code>value_copy</code></em> with a copy of the header field. <em class="parameter"><code>value_copy</code></em> must be zeroed
but uninitialised.
</p>
<p>
This will return -1 and add a message to the error buffer if the field
does not exist. Use <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a> to test for the
existence
of a field first if you are not certain it will be there.
</p>
<p>
For example, to read a double from an image (though of course you would use
<a class="link" href="libvips-header.html#vips-image-get-double" title="vips_image_get_double ()"><code class="function">vips_image_get_double()</code></a> in practice):
</p>
<p>
</p>
<div class="informalexample"><pre class="programlisting">
GValue value = { 0 };
double d;
if( vips_image_get( image, field, &value ) )
return( -1 );
if( G_VALUE_TYPE( &value ) != G_TYPE_DOUBLE ) {
vips_error( "mydomain",
_( "field \"%s\" is of type %s, not double" ),
field,
g_type_name( G_VALUE_TYPE( &value ) ) );
g_value_unset( &value );
return( -1 );
}
d = g_value_get_double( &value );
g_value_unset( &value );
return( 0 );
</pre></div>
<p>
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a>, <a class="link" href="libvips-header.html#vips-image-get-double" title="vips_image_get_double ()"><code class="function">vips_image_get_double()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to get the field from from</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>the name to give the metadata</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>value_copy</code></em> :</span></p></td>
<td>the GValue is copied into this</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, -1 otherwise.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-as-string"></a><h3>vips_image_get_as_string ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get_as_string (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">char</span> **out</code></em>);</pre>
<p>
Gets <em class="parameter"><code>out</code></em> from <em class="parameter"><code>im</code></em> under the name <em class="parameter"><code>field</code></em>.
This function will read any field, returning it as a printable string.
You need to free the string with <code class="function">g_free()</code> when you are done with it.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()"><code class="function">vips_image_get()</code></a>, <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to get the header field from</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>field name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td>
<td>return field value as string</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, -1 otherwise.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-typeof"></a><h3>vips_image_get_typeof ()</h3>
<pre class="programlisting"><span class="returnvalue">GType</span> vips_image_get_typeof (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>);</pre>
<p>
Read the GType for a header field. Returns zero if there is no
field of that name.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()"><code class="function">vips_image_get()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to test</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>the name to search for</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the GType of the field, or zero if there is no
field of that name.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-remove"></a><h3>vips_image_remove ()</h3>
<pre class="programlisting"><span class="returnvalue">gboolean</span> vips_image_remove (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>);</pre>
<p>
Find and remove an item of metadata. Return <code class="literal">FALSE</code> if no metadata of that
name was found.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-set" title="vips_image_set ()"><code class="function">vips_image_set()</code></a>, <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to test</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>the name to search for</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>
<code class="literal">TRUE</code> if an item of metadata of that name was found and removed</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="VipsImageMapFn"></a><h3>VipsImageMapFn ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> * (*VipsImageMapFn) (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">GValue</span> *value</code></em>,
<em class="parameter"><code><span class="type">void</span> *a</code></em>);</pre>
<p>
</p>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-map"></a><h3>vips_image_map ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> * vips_image_map (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code><a class="link" href="libvips-header.html#VipsImageMapFn" title="VipsImageMapFn ()"><span class="type">VipsImageMapFn</span></a> fn</code></em>,
<em class="parameter"><code><span class="type">void</span> *a</code></em>);</pre>
<p>
This function calls <em class="parameter"><code>fn</code></em> for every header field, including every item of
metadata.
</p>
<p>
Like all _map functions, the user function should return <code class="literal">NULL</code> to continue
iteration, or a non-<code class="literal">NULL</code> pointer to indicate early termination.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a>, <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()"><code class="function">vips_image_get()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to map over</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>fn</code></em> :</span></p></td>
<td>function to call for each header field</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>a</code></em> :</span></p></td>
<td>user data for function</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>
<code class="literal">NULL</code> on success, the failing pointer otherwise.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-set-area"></a><h3>vips_image_set_area ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> vips_image_set_area (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">VipsCallbackFn</span> free_fn</code></em>,
<em class="parameter"><code><span class="type">void</span> *data</code></em>);</pre>
<p>
Attaches <em class="parameter"><code>data</code></em> as a metadata item on <em class="parameter"><code>image</code></em> under the name <em class="parameter"><code>field</code></em>. When
VIPS no longer needs the metadata, it will be freed with <em class="parameter"><code>free_fn</code></em>.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get-double" title="vips_image_get_double ()"><code class="function">vips_image_get_double()</code></a>, <a class="link" href="libvips-header.html#vips-image-set" title="vips_image_set ()"><code class="function">vips_image_set()</code></a>
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to attach the metadata to</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>metadata name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>free_fn</code></em> :</span></p></td>
<td>free function for <em class="parameter"><code>data</code></em>. <span class="annotation">[<acronym title="The callback is valid until first called."><span class="acronym">scope async</span></acronym>]</span>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>data</code></em> :</span></p></td>
<td>pointer to area of memory</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-area"></a><h3>vips_image_get_area ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get_area (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">void</span> **data</code></em>);</pre>
<p>
Gets <em class="parameter"><code>data</code></em> from <em class="parameter"><code>image</code></em> under the name <em class="parameter"><code>field</code></em>. A convenience
function over <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()"><code class="function">vips_image_get()</code></a>. Use <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a> to test for
the existance of a piece of metadata.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-set-area" title="vips_image_set_area ()"><code class="function">vips_image_set_area()</code></a>, <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()"><code class="function">vips_image_get()</code></a>,
<a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a>
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to get the metadata from</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>metadata name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>data</code></em> :</span></p></td>
<td>return metadata value</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, -1 otherwise.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-set-blob"></a><h3>vips_image_set_blob ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> vips_image_set_blob (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">VipsCallbackFn</span> free_fn</code></em>,
<em class="parameter"><code><span class="type">void</span> *data</code></em>,
<em class="parameter"><code><span class="type">size_t</span> length</code></em>);</pre>
<p>
Attaches <em class="parameter"><code>blob</code></em> as a metadata item on <em class="parameter"><code>image</code></em> under the name <em class="parameter"><code>field</code></em>. A
convenience
function over <a class="link" href="libvips-header.html#vips-image-set" title="vips_image_set ()"><code class="function">vips_image_set()</code></a> using an vips_blob.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get-blob" title="vips_image_get_blob ()"><code class="function">vips_image_get_blob()</code></a>, <a class="link" href="libvips-header.html#vips-image-set" title="vips_image_set ()"><code class="function">vips_image_set()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to attach the metadata to</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>metadata name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>free_fn</code></em> :</span></p></td>
<td>free function for <em class="parameter"><code>data</code></em>. <span class="annotation">[<acronym title="The callback is valid until first called."><span class="acronym">scope async</span></acronym>]</span>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>data</code></em> :</span></p></td>
<td>pointer to area of memory</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>length</code></em> :</span></p></td>
<td>length of memory area</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-blob"></a><h3>vips_image_get_blob ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get_blob (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">void</span> **data</code></em>,
<em class="parameter"><code><span class="type">size_t</span> *length</code></em>);</pre>
<p>
Gets <em class="parameter"><code>blob</code></em> from <em class="parameter"><code>image</code></em> under the name <em class="parameter"><code>field</code></em>, optionally return its length in
<em class="parameter"><code>length</code></em>. A convenience
function over <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()"><code class="function">vips_image_get()</code></a>. Use <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a> to test for the
existance
of a piece of metadata.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()"><code class="function">vips_image_get()</code></a>, <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a>, <code class="function">vips_blob_get()</code>,
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to get the metadata from</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>metadata name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>data</code></em> :</span></p></td>
<td>pointer to area of memory</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>length</code></em> :</span></p></td>
<td>return the blob length here, optionally</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, -1 otherwise.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-int"></a><h3>vips_image_get_int ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get_int (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">int</span> *out</code></em>);</pre>
<p>
Gets <em class="parameter"><code>out</code></em> from <em class="parameter"><code>im</code></em> under the name <em class="parameter"><code>field</code></em>. This function searches for
int-valued fields.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()"><code class="function">vips_image_get()</code></a>, <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a>
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to get the header field from</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>field name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td>
<td>return field value</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, -1 otherwise.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-set-int"></a><h3>vips_image_set_int ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> vips_image_set_int (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">int</span> i</code></em>);</pre>
<p>
Attaches <em class="parameter"><code>i</code></em> as a metadata item on <em class="parameter"><code>image</code></em> under the name <em class="parameter"><code>field</code></em>. A
convenience
function over <a class="link" href="libvips-header.html#vips-image-set" title="vips_image_set ()"><code class="function">vips_image_set()</code></a>.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get-int" title="vips_image_get_int ()"><code class="function">vips_image_get_int()</code></a>, <a class="link" href="libvips-header.html#vips-image-set" title="vips_image_set ()"><code class="function">vips_image_set()</code></a>
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to attach the metadata to</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>metadata name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>i</code></em> :</span></p></td>
<td>metadata value</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-double"></a><h3>vips_image_get_double ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get_double (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">double</span> *out</code></em>);</pre>
<p>
Gets <em class="parameter"><code>out</code></em> from <em class="parameter"><code>im</code></em> under the name <em class="parameter"><code>field</code></em>.
This function searches for
double-valued fields.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()"><code class="function">vips_image_get()</code></a>, <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a>
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to get the header field from</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>field name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td>
<td>return field value</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, -1 otherwise.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-set-double"></a><h3>vips_image_set_double ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> vips_image_set_double (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code><span class="type">double</span> d</code></em>);</pre>
<p>
Attaches <em class="parameter"><code>d</code></em> as a metadata item on <em class="parameter"><code>image</code></em> under the name <em class="parameter"><code>field</code></em>. A
convenience
function over <a class="link" href="libvips-header.html#vips-image-set" title="vips_image_set ()"><code class="function">vips_image_set()</code></a>.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get-double" title="vips_image_get_double ()"><code class="function">vips_image_get_double()</code></a>, <a class="link" href="libvips-header.html#vips-image-set" title="vips_image_set ()"><code class="function">vips_image_set()</code></a>
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to attach the metadata to</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>metadata name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>d</code></em> :</span></p></td>
<td>metadata value</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-string"></a><h3>vips_image_get_string ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_get_string (<em class="parameter"><code>const <a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code>const <span class="type">char</span> **out</code></em>);</pre>
<p>
Gets <em class="parameter"><code>out</code></em> from <em class="parameter"><code>im</code></em> under the name <em class="parameter"><code>field</code></em>.
This function searches for string-valued fields.
</p>
<p>
Do not free <em class="parameter"><code>out</code></em>.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get" title="vips_image_get ()"><code class="function">vips_image_get()</code></a>, <a class="link" href="libvips-header.html#vips-image-get-typeof" title="vips_image_get_typeof ()"><code class="function">vips_image_get_typeof()</code></a>
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to get the header field from</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>field name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td>
<td>return field value</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, -1 otherwise.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-set-string"></a><h3>vips_image_set_string ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> vips_image_set_string (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *field</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *str</code></em>);</pre>
<p>
Attaches <em class="parameter"><code>str</code></em> as a metadata item on <em class="parameter"><code>image</code></em> under the name <em class="parameter"><code>field</code></em>.
A convenience
function over <a class="link" href="libvips-header.html#vips-image-set" title="vips_image_set ()"><code class="function">vips_image_set()</code></a> using an vips_ref_string.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get-double" title="vips_image_get_double ()"><code class="function">vips_image_get_double()</code></a>, <a class="link" href="libvips-header.html#vips-image-set" title="vips_image_set ()"><code class="function">vips_image_set()</code></a>, vips_ref_string
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to attach the metadata to</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>field</code></em> :</span></p></td>
<td>metadata name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>str</code></em> :</span></p></td>
<td>metadata value</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-history-printf"></a><h3>vips_image_history_printf ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_history_printf (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *format</code></em>,
<em class="parameter"><code>...</code></em>);</pre>
<p>
Add a line to the image history. The <em class="parameter"><code>format</code></em> and arguments are expanded, the
date and time is appended prefixed with a hash character, and the whole
string is appended to the image history and terminated with a newline.
</p>
<p>
For example:
</p>
<p>
</p>
<div class="informalexample"><pre class="programlisting">
vips_image_history_printf( image, "vips im_invert %s %s",
in->filename, out->filename );
</pre></div>
<p>
</p>
<p>
Might add the string
</p>
<p>
</p>
<div class="informalexample"><pre class="programlisting">
"vips im_invert /home/john/fred.v /home/john/jim.v # Fri Apr 3 23:30:35
2009\n"
</pre></div>
<p>
</p>
<p>
VIPS operations don't add history lines for you because a single action at
the application level might involve many VIPS operations. History must be
recorded by the application.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>add history line to this image</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>format</code></em> :</span></p></td>
<td>printf() format string</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, -1 on error.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-history-args"></a><h3>vips_image_history_args ()</h3>
<pre class="programlisting"><span class="returnvalue">int</span> vips_image_history_args (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>,
<em class="parameter"><code>const <span class="type">char</span> *name</code></em>,
<em class="parameter"><code><span class="type">int</span> argc</code></em>,
<em class="parameter"><code><span class="type">char</span> *argv[]</code></em>);</pre>
<p>
Formats the name/argv as a single string and calls
<a class="link" href="libvips-header.html#vips-image-history-printf" title="vips_image_history_printf ()"><code class="function">vips_image_history_printf()</code></a>. A
convenience function for command-line prorams.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-get-history" title="vips_image_get_history ()"><code class="function">vips_image_get_history()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>image to attach history line to</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>name</code></em> :</span></p></td>
<td>program name</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>argc</code></em> :</span></p></td>
<td>number of program arguments</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>argv</code></em> :</span></p></td>
<td>program arguments</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>0 on success, -1 on error.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="vips-image-get-history"></a><h3>vips_image_get_history ()</h3>
<pre class="programlisting">const <span class="returnvalue">char</span> * vips_image_get_history (<em class="parameter"><code><a class="link" href="VipsImage.html" title="VipsImage"><span class="type">VipsImage</span></a> *image</code></em>);</pre>
<p>
This function reads the image history as a C string. The string is owned
by VIPS and must not be freed.
</p>
<p>
VIPS tracks the history of each image, that is, the sequence of operations
that generated that image. Applications built on VIPS need to call
<a class="link" href="libvips-header.html#vips-image-history-printf" title="vips_image_history_printf ()"><code class="function">vips_image_history_printf()</code></a> for each action they perform, setting the
command-line equivalent for the action.
</p>
<p>
See also: <a class="link" href="libvips-header.html#vips-image-history-printf" title="vips_image_history_printf ()"><code class="function">vips_image_history_printf()</code></a>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>image</code></em> :</span></p></td>
<td>get history from here</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>The history of <em class="parameter"><code>image</code></em> as a C string. Do not free!</td>
</tr>
</tbody>
</table></div>
</div>
</div>
<div class="refsect1">
<a name="libvips-header.see-also"></a><h2>See Also</h2>
meta,
check
</div>
</div>
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