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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | <html><head><title>The ImageChops Module</title><link rel="stylesheet" type="text/css" href="effbot.css" /></head><body><div id="IMAGECHOPS-MODULE" class="chapter"><h1 style="chapter">The ImageChops Module</h1><p>This module contains a number of arithmetical image operations,
called <i>channel operations</i>
(<span>"chops"</span>). These can be used for various purposes,
including special effects, image compositions, algorithmic painting,
and more.</p><div class="sect1"><h2 style="sect1">Functions</h2><p>Most channel operations take one or two image arguments and
returns a new image. Unless otherwise noted, the result of a channel
operation is always clipped to the range 0 to MAX (which is 255 for
all modes supported by the operations in this module).</p><div class="sect2"><h3 style="sect2">constant</h3><p><tt>constant(image, value)</tt>. Return a layer with the
same size as the given image, but filled with the given pixel value.</p></div><div class="sect2"><h3 style="sect2">duplicate</h3><p><tt>duplicate(image)</tt>. Return a copy of the given
image.</p></div><div class="sect2"><h3 style="sect2">invert</h3><p><tt>invert(image)</tt>. Inverts an image.</p><pre> out = MAX - image</pre></div><div class="sect2"><h3 style="sect2">lighter</h3><p><tt>lighter(image1, image2)</tt>. Compares the two images,
pixels by pixel, and returns a new image containing the lighter value
for each pixel.</p><pre> out = max(image1, image2)</pre></div><div class="sect2"><h3 style="sect2">darker</h3><p><tt>darker(image1, image2)</tt>. Compares the two images,
pixels by pixel, and returns a new image containing the darker value
for each pixel.</p><pre> out = min(image1, image2)</pre></div><div class="sect2"><h3 style="sect2">difference</h3><p><tt>difference(image1, image2)</tt>. Returns the absolute
value of the difference between the two images.</p><pre> out = abs(image1 - image2)</pre></div><div class="sect2"><h3 style="sect2">multiply</h3><p><tt>multiply(image1, image2)</tt>. Superimposes two images
on top of each other. If you multiply an image with a solid black
image, the result is black. If you multiply with a solid white image,
the image is unaffected.</p><pre> out = image1 * image2 / MAX</pre></div><div class="sect2"><h3 style="sect2">screen</h3><p><tt>screen(image1, image2)</tt>. Superimposes two inverted
images on top of each other.</p><pre> out = MAX - ((MAX - image1) * (MAX - image2) / MAX)</pre></div><div class="sect2"><h3 style="sect2">add</h3><p><tt>add(image1, image2, scale, offset)</tt>. Adds two
images, dividing the result by scale and adding the offset. If
omitted, scale defaults to 1.0, and offset to 0.0.</p><pre> out = (image1 + image2) / scale + offset</pre></div><div class="sect2"><h3 style="sect2">subtract</h3><p><tt>subtract(image1, image2, scale, offset)</tt>. Subtracts
two images, dividing the result by scale and adding the offset. If
omitted, scale defaults to 1.0, and offset to 0.0.</p><pre> out = (image1 - image2) / scale + offset</pre></div><div class="sect2"><h3 style="sect2">blend</h3><p><tt>blend(image1, image2, alpha)</tt>. Same as the
<tt>blend</tt> function in the
<tt>Image</tt> module.</p></div><div class="sect2"><h3 style="sect2">composite</h3><p><tt>composite(image1, image2, mask)</tt>. Same as the
<tt>composite</tt> function in the
<tt>Image</tt> module.</p></div><div class="sect2"><h3 style="sect2">offset</h3><p>(Deprecated) <tt>offset(xoffset, yoffset)</tt>. Returns a
copy of the image where data have been offset by the given
distances. Data wraps around the edges. If yoffset is omitted, it is
assumed to be equal to xoffset.</p></div></div></div></body></html>
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