On Sun, Feb 25, 2007 at 07:01:50PM -0400, bulia byak wrote:
Here's a message from a cairo developer - not sure if it reached our list, so I'm forwarding it. It confirms that my initial description was indeed incorrect: Inkscape uses fixed order, while Cairo's order depends on platform. Sorry for the confusion (though it amounts to the same thing from compatibility viewpoint). However, Inkscape's code assumes a fixed byte order (see below). i.e R is byte 0, G is byte 1 etc.
r = NR_RGBA32_R (rgba); g = NR_RGBA32_G (rgba); b = NR_RGBA32_B (rgba); a = NR_RGBA32_A (rgba);
These macros along with a lot of others that appear to do similar rgba operations are in nr-pixops.h. Perhaps a starting point would be to put #ifdefs around them and provide cairo-compatible versions of each, if some define is specified.
for (y = h; y > 0; y--) { if (a == 0) { memset(px, 0, w*4); } else { unsigned char *d = px; const unsigned char *m = mpx; for (x = w; x > 0; x--) { d[0] = r; d[1] = g; d[2] = b; d[3] = NR_PREMUL_111 (m[0], a);
Next would be to find all the places where byte-order dependent operations are being done, and add new macros in nr-pixops.h or some other central place for those things that allow them to be ifdef'd as well.
Bryce