operator-alpha-alpha.c [plain text]
#include "cairo-test.h"
#define STEPS 16
#define START_OPERATOR CAIRO_OPERATOR_CLEAR
#define STOP_OPERATOR CAIRO_OPERATOR_HSL_LUMINOSITY
#define SIZE 3
#define COUNT 6
#define FULL_WIDTH ((STEPS + 1) * COUNT - 1)
#define FULL_HEIGHT ((COUNT + STOP_OPERATOR - START_OPERATOR) / COUNT) * (STEPS + 1)
static void
create_patterns (cairo_t *bg, cairo_t *fg)
{
int x;
for (x = 0; x < STEPS; x++) {
double i = (double) x / (STEPS - 1);
cairo_set_source_rgba (bg, 0, 0, 0, i);
cairo_rectangle (bg, x, 0, 1, STEPS);
cairo_fill (bg);
cairo_set_source_rgba (fg, 0, 0, 0, i);
cairo_rectangle (fg, 0, x, STEPS, 1);
cairo_fill (fg);
}
}
static void
do_composite (cairo_t *cr, cairo_operator_t op, cairo_surface_t *bg, cairo_surface_t *fg)
{
cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
cairo_set_source_surface (cr, bg, 0, 0);
cairo_paint (cr);
cairo_set_operator (cr, op);
cairo_set_source_surface (cr, fg, 0, 0);
cairo_paint (cr);
}
static void
subdraw (cairo_t *cr, int width, int height)
{
size_t i = 0;
cairo_operator_t op;
cairo_t *bgcr, *fgcr;
cairo_surface_t *bg, *fg;
bg = cairo_surface_create_similar (cairo_get_target (cr),
CAIRO_CONTENT_COLOR_ALPHA, SIZE * STEPS, SIZE * STEPS);
fg = cairo_surface_create_similar (cairo_get_target (cr),
CAIRO_CONTENT_COLOR_ALPHA, SIZE * STEPS, SIZE * STEPS);
bgcr = cairo_create (bg);
fgcr = cairo_create (fg);
cairo_scale (bgcr, SIZE, SIZE);
cairo_scale (fgcr, SIZE, SIZE);
create_patterns (bgcr, fgcr);
cairo_destroy (bgcr);
cairo_destroy (fgcr);
for (op = START_OPERATOR; op <= STOP_OPERATOR; op++, i++) {
cairo_save (cr);
cairo_translate (cr,
SIZE * (STEPS + 1) * (i % COUNT),
SIZE * (STEPS + 1) * (i / COUNT));
cairo_rectangle (cr, 0, 0, SIZE * (STEPS + 1), SIZE * (STEPS+1));
cairo_clip (cr);
do_composite (cr, op, bg, fg);
cairo_restore (cr);
}
cairo_surface_destroy (fg);
cairo_surface_destroy (bg);
}
static cairo_surface_t *
create_source (cairo_surface_t *target, int width, int height)
{
cairo_surface_t *similar;
cairo_t *cr;
similar = cairo_surface_create_similar (target,
CAIRO_CONTENT_ALPHA,
width, height);
cr = cairo_create (similar);
cairo_surface_destroy (similar);
subdraw (cr, width, height);
similar = cairo_surface_reference (cairo_get_target (cr));
cairo_destroy (cr);
return similar;
}
static cairo_test_status_t
draw (cairo_t *cr, int width, int height)
{
cairo_surface_t *source;
cairo_set_source_rgb (cr, 1, 1, 1);
cairo_paint (cr);
source = create_source (cairo_get_target (cr), width, height);
cairo_set_source_surface (cr, source, 0, 0);
cairo_surface_destroy (source);
cairo_paint (cr);
return CAIRO_TEST_SUCCESS;
}
CAIRO_TEST (operator_alpha_alpha,
"Tests result of compositing pure-alpha surfaces"
"\nCompositing of pure-alpha sources is inconsistent across backends.",
"alpha, similar, operator",
NULL,
FULL_WIDTH * SIZE, FULL_HEIGHT * SIZE,
NULL, draw)