| Summary: | Rounding error introduced in recent commit | ||
|---|---|---|---|
| Product: | cairo | Reporter: | Jens Taprogge <jlt_fdo> |
| Component: | pdf backend | Assignee: | Kristian Høgsberg <krh> |
| Status: | RESOLVED NOTABUG | QA Contact: | cairo-bugs mailing list <cairo-bugs> |
| Severity: | normal | ||
| Priority: | high | ||
| Version: | 1.1.1 | ||
| Hardware: | x86 (IA32) | ||
| OS: | Linux (All) | ||
| Whiteboard: | |||
| i915 platform: | i915 features: | ||
Given the old code, the correct conversion is what I noted here: http://lists.freedesktop.org/archives/cairo/2005-October/005433.html ie, stops[i].color_char[0] = pattern->stops[i].color.red * 0xff + 0.5; should be changed to something like this: stops[i].color_char[0] = pattern->stops[i].color.red * (256 - 1e-5); but now that stops[i].color_char[0] are uchars, the current code is correct, cause, we want to have a uniform mapping, and that's what we've got: 0000-00ff -> 00 0100-01ff -> 01 ... ff00-ffff -> ff So each target bin is stuffed with exactly 0x100 source items. Perfect. In other words, no, 0x12ff should map to 0x12, cause we cannot map 0xffff to 0x100 anyway... |
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I think a recent commit introduced a rounding error in the PDF backend: Index: cairo-pdf-surface.c =================================================================== RCS file: /cvs/cairo/cairo/src/cairo-pdf-surface.c,v retrieving revision 1.69 retrieving revision 1.70 diff -u -d -r1.69 -r1.70 --- cairo-pdf-surface.c 16 Dec 2005 11:02:35 -0000 1.69 +++ cairo-pdf-surface.c 5 Jan 2006 13:06:50 -0000 1.70 @@ -971,11 +971,11 @@ n_stops = pattern->n_stops; for (i = 0; i < pattern->n_stops; i++) { - stops[i].color_char[0] = pattern->stops[i].color.red * 0xff + 0.5; - stops[i].color_char[1] = pattern->stops[i].color.green * 0xff + 0.5; - stops[i].color_char[2] = pattern->stops[i].color.blue * 0xff + 0.5; - stops[i].color_char[3] = pattern->stops[i].color.alpha * 0xff + 0.5; - stops[i].offset = _cairo_fixed_to_double (pattern->stops[i].offset); + stops[i].color_char[0] = pattern->stops[i].color.red >> 8; + stops[i].color_char[1] = pattern->stops[i].color.green >> 8; + stops[i].color_char[2] = pattern->stops[i].color.blue >> 8; + stops[i].color_char[3] = pattern->stops[i].color.alpha >> 8; + stops[i].offset = _cairo_fixed_to_double (pattern->stops[i].x); stops[i].id = i; } The colour conversion should rather be: stops[i].color_char[0] = (pattern->stops[i].color.red + 0x80) >> 8; stops[i].color_char[1] = (pattern->stops[i].color.green + 0x80) >> 8; stops[i].color_char[2] = (pattern->stops[i].color.blue + 0x80) >> 8; stops[i].color_char[3] = (pattern->stops[i].color.alpha + 0x80) >> 8; (Think of a color value such as 0x12ff which should obviously be converted to 0x13) Jens