colour spaces for a given image. For instance, if pipi_gaussian_blur is
    applied to a 32-bpp image, it is automatically converted to gamma-corrected
    32-bit floats beforehands, then converted back to normal.
  * TODO: clipping, regions of interest, more formats, getpixel macros...

git-svn-id: file:///srv/caca.zoy.org/var/lib/svn/libpipi/trunk@2605 92316355-f0b4-4df1-b90c-862c8a59935f