I'm implementing SVG support for TuxMath and TuxType as a GSOC project.
I would like to base my SVG loading code on what is already implemented in TuxPaint and I have a question about the color masks that are being set in load_svg() function in tuxpaint.c
Where do these values:

  rmask = 0x00ff0000;
  gmask = 0x0000ff00;
  bmask = 0x000000ff;
  amask = 0xff000000;

come from ? I tried to use SDL_CreateRGBSurface with different ones depending on SDL_BYTEORDER but the svg wasn't displayed correctly. Are values used in tuxpaint some cairo- or librsvg-related constants ? If os, are they independent on endianness ?

kind regards,
Bolesław Kulbabiński