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test/coverage: Exercise invariance under mirror symmetry

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Massimo noticed that the record/record-flip were not being rasterised as
identical mirror images due to a half-subpixel offset in the tor scan
converter. This test attempts to reproduce this error by rendering a
rhombus around the origin of each cell (that is it generates 4 mirror
images of a triangle in the 4 different orientations0. The expectation
is that each pixel in the group is lit identically as the coverage is
identical.

References: https://bugs.freedesktop.org/show_bug.cgi?id=84396
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
This commit is contained in:
Chris Wilson 2014-09-29 08:37:56 +01:00
parent fbb0a260b7
commit 5c03b20732
2 changed files with 55 additions and 0 deletions
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55
test/coverage.c
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@ -98,6 +98,54 @@ rectangles (cairo_t *cr, int width, int height)
return CAIRO_TEST_SUCCESS;
}
static cairo_test_status_t
rhombus (cairo_t *cr, int width, int height)
{
int x, y;
cairo_set_source_rgb (cr, 0.0, 0.0, 0.0);
cairo_paint (cr);
#if GENERATE_REFERENCE
for (y = 0; y < WIDTH; y++) {
for (x = 0; x < WIDTH; x++) {
cairo_set_source_rgba (cr, 1, 1, 1,
x * y / (2. * WIDTH * WIDTH));
cairo_rectangle (cr, 2*x, 2*y, 2, 2);
cairo_fill (cr);
}
}
#else
cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
cairo_set_source_rgb (cr, 1, 1, 1);
for (y = 0; y < WIDTH; y++) {
double yf = y / (double) WIDTH;
for (x = 0; x < WIDTH; x++) {
double xf = x / (double) WIDTH;
cairo_move_to (cr,
2*x + 1 - xf,
2*y + 1);
cairo_line_to (cr,
2*x + 1,
2*y + 1 - yf);
cairo_line_to (cr,
2*x + 1 + xf,
2*y + 1);
cairo_line_to (cr,
2*x + 1,
2*y + 1 + yf);
cairo_close_path (cr);
}
}
cairo_fill (cr);
#endif
return CAIRO_TEST_SUCCESS;
}
static cairo_test_status_t
intersecting_quads (cairo_t *cr, int width, int height)
{
@ -365,6 +413,13 @@ CAIRO_TEST (coverage_rectangles,
WIDTH, HEIGHT,
NULL, rectangles)
CAIRO_TEST (coverage_rhombus,
"Check the fidelity of the rasterisation.",
NULL, /* keywords */
"target=raster slow", /* requirements */
2*WIDTH, 2*WIDTH,
NULL, rhombus)
CAIRO_TEST (coverage_intersecting_quads,
"Check the fidelity of the rasterisation.",
NULL, /* keywords */

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