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image: Round down when rendering antialiased boxes

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Matches Pixman's output when going via pixman_rasterize_trapezoid()
This commit is contained in:
Benjamin Otte 2010-04-29 22:12:02 +02:00
parent 95179a5de9
commit 6d36f06751
2 changed files with 11 additions and 4 deletions
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6
src/cairo-fixed-private.h
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@ -165,6 +165,12 @@ _cairo_fixed_integer_round (cairo_fixed_t f)
return (f + (CAIRO_FIXED_FRAC_MASK+1)/2) >> CAIRO_FIXED_FRAC_BITS;
}
static inline int
_cairo_fixed_integer_round_down (cairo_fixed_t f)
{
return (f + CAIRO_FIXED_FRAC_MASK/2) >> CAIRO_FIXED_FRAC_BITS;
}
static inline int
_cairo_fixed_fractional_part (cairo_fixed_t f)
{

9
src/cairo-image-surface.c
View file

@ -2864,10 +2864,11 @@ _composite_boxes (cairo_image_surface_t *dst,
cairo_box_t *box = chunk->base;
for (i = 0; i < chunk->count; i++) {
int x1 = _cairo_fixed_integer_round (box[i].p1.x);
int y1 = _cairo_fixed_integer_round (box[i].p1.y);
int x2 = _cairo_fixed_integer_round (box[i].p2.x);
int y2 = _cairo_fixed_integer_round (box[i].p2.y);
/* round down here to match Pixman's behavior when using traps. */
int x1 = _cairo_fixed_integer_round_down (box[i].p1.x);
int y1 = _cairo_fixed_integer_round_down (box[i].p1.y);
int x2 = _cairo_fixed_integer_round_down (box[i].p2.x);
int y2 = _cairo_fixed_integer_round_down (box[i].p2.y);
if (x2 == x1 || y2 == y1)
continue;