[cairo-bugs] [Bug 5824] New: Rounding error introduced in recent commit

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https://bugs.freedesktop.org/show_bug.cgi?id=5824          
     
           Summary: Rounding error introduced in recent commit
           Product: cairo
           Version: 1.1.1
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: pdf backend
        AssignedTo: krh at bitplanet.net
        ReportedBy: jlt_fdo at shamrock.dyndns.org
         QAContact: cairo-bugs at cairographics.org


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          
     
     
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