/usr/lib/python2.7/dist-packages/cairocffi/pixbuf.py is in python-cairocffi 0.7.2-2.
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"""
cairocffi.pixbuf
~~~~~~~~~~~~~~~~
Loading various image formats with GDK-PixBuf
:copyright: Copyright 2013 by Simon Sapin
:license: BSD, see LICENSE for details.
"""
import sys
from io import BytesIO
from functools import partial
from array import array
from . import dlopen, ImageSurface, Context, constants
from .compat import xrange
try:
from ._ffi_pixbuf import ffi
except ImportError:
# PyPy < 2.6 compatibility
from .ffi_build import ffi_pixbuf as ffi
__all__ = ['decode_to_image_surface']
gdk_pixbuf = dlopen(ffi, 'gdk_pixbuf-2.0', 'gdk_pixbuf-2.0-0')
gobject = dlopen(ffi, 'gobject-2.0', 'gobject-2.0-0')
glib = dlopen(ffi, 'glib-2.0', 'glib-2.0-0')
try:
gdk = dlopen(ffi, 'gdk-3', 'gdk-x11-2.0', 'gdk-win32-2.0-0')
except OSError:
gdk = None
gobject.g_type_init()
class ImageLoadingError(ValueError):
"""PixBuf returned an error when loading an image.
The image data is probably corrupted.
"""
def handle_g_error(error, return_value):
"""Convert a :c:type:`GError**` to a Python :exception:`ImageLoadingError`,
and raise it.
"""
error = error[0]
assert bool(return_value) == (error == ffi.NULL)
if error != ffi.NULL:
if error.message != ffi.NULL:
message = ('Pixbuf error: ' +
ffi.string(error.message).decode('utf8', 'replace'))
else:
message = 'Pixbuf error'
glib.g_error_free(error)
raise ImageLoadingError(message)
class Pixbuf(object):
"""Wrap a :c:type:`GdkPixbuf` pointer and simulate methods."""
def __init__(self, pointer):
gobject.g_object_ref(pointer)
self._pointer = ffi.gc(pointer, gobject.g_object_unref)
def __getattr__(self, name):
function = getattr(gdk_pixbuf, 'gdk_pixbuf_' + name)
return partial(function, self._pointer)
def decode_to_pixbuf(image_data):
"""Decode an image from memory with GDK-PixBuf.
The file format is detected automatically.
:param image_data: A byte string
:returns:
A tuple of a new :class:`PixBuf` object
and the name of the detected image format.
:raises:
:exc:`ImageLoadingError` if the image data is invalid
or in an unsupported format.
"""
loader = ffi.gc(
gdk_pixbuf.gdk_pixbuf_loader_new(), gobject.g_object_unref)
error = ffi.new('GError **')
handle_g_error(error, gdk_pixbuf.gdk_pixbuf_loader_write(
loader, ffi.new('guchar[]', image_data), len(image_data), error))
handle_g_error(error, gdk_pixbuf.gdk_pixbuf_loader_close(loader, error))
format_ = gdk_pixbuf.gdk_pixbuf_loader_get_format(loader)
format_name = (
ffi.string(gdk_pixbuf.gdk_pixbuf_format_get_name(format_))
.decode('ascii')
if format_ != ffi.NULL else None)
pixbuf = gdk_pixbuf.gdk_pixbuf_loader_get_pixbuf(loader)
if pixbuf == ffi.NULL:
raise ImageLoadingError('Not enough image data (got a NULL pixbuf.)')
return Pixbuf(pixbuf), format_name
def decode_to_image_surface(image_data):
"""Decode an image from memory into a cairo surface.
The file format is detected automatically.
:param image_data: A byte string
:returns:
A tuple of a new :class:`~cairocffi.ImageSurface` object
and the name of the detected image format.
:raises:
:exc:`ImageLoadingError` if the image data is invalid
or in an unsupported format.
"""
pixbuf, format_name = decode_to_pixbuf(image_data)
surface = (
pixbuf_to_cairo_gdk(pixbuf) if gdk is not None
else pixbuf_to_cairo_slices(pixbuf) if not pixbuf.get_has_alpha()
else pixbuf_to_cairo_png(pixbuf))
return surface, format_name
def pixbuf_to_cairo_gdk(pixbuf):
"""Convert from PixBuf to ImageSurface, using GDK.
This method is fastest but GDK is not always available.
"""
dummy_context = Context(ImageSurface(constants.FORMAT_ARGB32, 1, 1))
gdk.gdk_cairo_set_source_pixbuf(
dummy_context._pointer, pixbuf._pointer, 0, 0)
return dummy_context.get_source().get_surface()
def pixbuf_to_cairo_slices(pixbuf):
"""Convert from PixBuf to ImageSurface, using slice-based byte swapping.
This method is 2~5x slower than GDK but does not support an alpha channel.
(cairo uses pre-multiplied alpha, but not Pixbuf.)
"""
assert pixbuf.get_colorspace() == gdk_pixbuf.GDK_COLORSPACE_RGB
assert pixbuf.get_n_channels() == 3
assert pixbuf.get_bits_per_sample() == 8
width = pixbuf.get_width()
height = pixbuf.get_height()
rowstride = pixbuf.get_rowstride()
pixels = ffi.buffer(pixbuf.get_pixels(), pixbuf.get_byte_length())
# TODO: remove this when cffi buffers support slicing with a stride.
pixels = pixels[:]
# Convert GdkPixbuf’s big-endian RGBA to cairo’s native-endian ARGB
cairo_stride = ImageSurface.format_stride_for_width(
constants.FORMAT_RGB24, width)
data = bytearray(cairo_stride * height)
big_endian = sys.byteorder == 'big'
pixbuf_row_length = width * 3 # stride == row_length + padding
cairo_row_length = width * 4 # stride == row_length + padding
alpha = b'\xff' * width # opaque
for y in xrange(height):
offset = rowstride * y
end = offset + pixbuf_row_length
red = pixels[offset:end:3]
green = pixels[offset + 1:end:3]
blue = pixels[offset + 2:end:3]
offset = cairo_stride * y
end = offset + cairo_row_length
if big_endian: # pragma: no cover
data[offset:end:4] = alpha
data[offset + 1:end:4] = red
data[offset + 2:end:4] = green
data[offset + 3:end:4] = blue
else:
data[offset + 3:end:4] = alpha
data[offset + 2:end:4] = red
data[offset + 1:end:4] = green
data[offset:end:4] = blue
data = array('B', data)
return ImageSurface(constants.FORMAT_RGB24,
width, height, data, cairo_stride)
def pixbuf_to_cairo_png(pixbuf):
"""Convert from PixBuf to ImageSurface, by going through the PNG format.
This method is 10~30x slower than GDK but always works.
"""
buffer_pointer = ffi.new('gchar **')
buffer_size = ffi.new('gsize *')
error = ffi.new('GError **')
handle_g_error(error, pixbuf.save_to_buffer(
buffer_pointer, buffer_size, ffi.new('char[]', b'png'), error,
ffi.new('char[]', b'compression'), ffi.new('char[]', b'0'),
ffi.NULL))
png_bytes = ffi.buffer(buffer_pointer[0], buffer_size[0])
return ImageSurface.create_from_png(BytesIO(png_bytes))
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