diff options
| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | src/cairo-color.c | 28 |
2 files changed, 15 insertions, 19 deletions
@@ -1,5 +1,11 @@ 2005-08-13 Behdad Esfahbod <behdad@behdad.org> + * src/cairo-color.c: Fix conversion to short, to get a uniform + range even for 0xffff. In other words, a color component of + of (1.0 - epsilon) would convert to 0xffff, not 0xfffe. + +2005-08-13 Behdad Esfahbod <behdad@behdad.org> + * RELEASING: * Makefile.am: Generate sh1sum instead of md5sum. Use gpg to sign it. You need gpg set up. diff --git a/src/cairo-color.c b/src/cairo-color.c index beb4a347..e202af24 100644 --- a/src/cairo-color.c +++ b/src/cairo-color.c @@ -89,29 +89,19 @@ _cairo_color_init_rgb (cairo_color_t *color, _cairo_color_init_rgba (color, red, green, blue, 1.0); } +/* We multiply colors by (0x10000 - epsilon), such that we get a uniform + * range even for 0xffff. In other words, (1.0 - epsilon) would convert + * to 0xffff, not 0xfffe. + */ +#define CAIRO_COLOR_ONE_MINUS_EPSILON (65536.0 - 1e-5) -/* XXX: The calculation of: - - channel * 0xffff - - isn't really what we want since: - - (1.0 - epsilon) * 0xffff = 0xfffe - - In other words, given an input range of [0.0, 1.0], we have an - infinitely small range tha maps to the output value 0xffff, - (while having large, uniformly sized input ranges for all - other output values). This is undesirable, particularly when - we want to do optimizations for "opaque" colors specfied as - floating-point. -*/ static void _cairo_color_compute_shorts (cairo_color_t *color) { - color->red_short = color->red * color->alpha * 0xffff; - color->green_short = color->green * color->alpha * 0xffff; - color->blue_short = color->blue * color->alpha * 0xffff; - color->alpha_short = color->alpha * 0xffff; + color->red_short = color->red * color->alpha * CAIRO_COLOR_ONE_MINUS_EPSILON; + color->green_short = color->green * color->alpha * CAIRO_COLOR_ONE_MINUS_EPSILON; + color->blue_short = color->blue * color->alpha * CAIRO_COLOR_ONE_MINUS_EPSILON; + color->alpha_short = color->alpha * CAIRO_COLOR_ONE_MINUS_EPSILON; } void |