GdkPixbufs are not premultiplied, so when using them to display pixman
images, there is some unecessary conversions going on: First the image
is converted to non-premultiplied, and then GdkPixbuf premultiplies
before sending the result to the X server. These conversions may cause
the displayed image to not be exactly identical to the original.
This patch just uses a cairo image surface instead, which avoids these
conversions.
Also make the comment about sRGB a little more concise.
This makes show_image() deal with more formats than just a8r8g8b8, in
particular, a8r8g8b8_sRGB can now be handled.
Images that are passed to show_image with a format of a8r8g8b8_sRGB
are displayed without modification under the assumption that the
monitor is approximately sRGB.
Images with a format of a8r8g8b8 are also displayed without
modification since many other users of show_image() have been
generating essentially sRGB data with this format. Other formats are
also assumed to be gamma compressed; these are converted to a8r8g8b8
before being displayed.
With these changes, srgb-test.c doesn't need to do its own conversion
anymore.
This separates the test suite from the random gtk+ using test
programs. "demos" is somewhat misleading because the programs there
are not particularly exciting (with the possible exception of
composite-test which shows off all the compositing operators).
