test: Add partial coverage.

Another experiment in measuring consistency of rasterisation stratagems
across the backends.

1 files changed, 213 insertions, 0 deletions

diff --git a/test/partial-coverage.c b/test/partial-coverage.c
new file mode 100644
index 000000000..9df87d469
--- /dev/null
+++ b/test/partial-coverage.c
@@ -0,0 +1,213 @@
+/*
+ * Copyright 2010 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * Author: Chris Wilson <chris@chris-wilson.co.uk>
+ */
+
+#include "cairo-test.h"
+
+/* Test the sampling stratagems of the rasterisers by creating pixels
+ * containing minute holes and seeing how close to the expected
+ * coverage each rasteriser approaches.
+ */
+
+#define SIZE 64
+
+#include "../src/cairo-fixed-type-private.h"
+#define SAMPLE (1 << CAIRO_FIXED_FRAC_BITS)
+
+static uint32_t state;
+
+static uint32_t
+hars_petruska_f54_1_random (void)
+{
+#define rol(x,k) ((x << k) | (x >> (32-k)))
+    return state = (state ^ rol (state, 5) ^ rol (state, 24)) + 0x37798849;
+#undef rol
+}
+
+static double
+uniform_random (void)
+{
+    return hars_petruska_f54_1_random() / (double) UINT32_MAX;
+}
+
+/* coverage is given in [0,65535] */
+static void
+compute_occupancy (uint8_t *occupancy, int coverage)
+{
+    int i, c;
+
+    if (coverage < SAMPLE*SAMPLE/2) {
+	memset (occupancy, 0, SAMPLE*SAMPLE);
+	for (i = c = 0; i < SAMPLE*SAMPLE; i++) {
+	    if ((SAMPLE*SAMPLE - i) * uniform_random() < coverage - c) {
+		occupancy[i] = 0xff;
+		if (++c == coverage)
+		    return;
+	    }
+	}
+    } else {
+	coverage = SAMPLE*SAMPLE - coverage;
+	memset (occupancy, 0xff, SAMPLE*SAMPLE);
+	for (i = c = 0; i < SAMPLE*SAMPLE; i++) {
+	    if ((SAMPLE*SAMPLE - i) * uniform_random() < coverage - c) {
+		occupancy[i] = 0;
+		if (++c == coverage)
+		    return;
+	    }
+	}
+    }
+}
+
+static cairo_test_status_t
+reference (cairo_t *cr, int width, int height)
+{
+    int i;
+
+    cairo_set_source_rgb (cr, 0.0, 0.0, 0.0);
+    cairo_paint (cr);
+
+    for (i = 0; i < SIZE*SIZE; i++) {
+	cairo_set_source_rgba (cr, 1., 1., 1.,
+			       i / (double) (SIZE * SIZE));
+	cairo_rectangle (cr, i % SIZE, i / SIZE, 1, 1);
+	cairo_fill (cr);
+    }
+
+    return CAIRO_STATUS_SUCCESS;
+}
+
+static cairo_test_status_t
+rectangles (cairo_t *cr, int width, int height)
+{
+    uint8_t *occupancy;
+    int i, j, channel;
+
+    state = 0x12345678;
+    occupancy = xmalloc (SAMPLE*SAMPLE);
+
+    cairo_set_source_rgb (cr, 0.0, 0.0, 0.0);
+    cairo_paint (cr);
+
+    cairo_set_operator (cr, CAIRO_OPERATOR_ADD);
+    for (channel = 0; channel < 3; channel++) {
+	switch (channel) {
+	default:
+	case 0: cairo_set_source_rgb (cr, 1.0, 0.0, 0.0); break;
+	case 1: cairo_set_source_rgb (cr, 0.0, 1.0, 0.0); break;
+	case 2: cairo_set_source_rgb (cr, 0.0, 0.0, 1.0); break;
+	}
+
+	for (i = 0; i < SIZE*SIZE; i++) {
+	    int xs, ys;
+
+	    compute_occupancy (occupancy, SAMPLE*SAMPLE * i / (SIZE * SIZE));
+
+	    xs = i % SIZE * SAMPLE;
+	    ys = i / SIZE * SAMPLE;
+	    for (j = 0; j < SAMPLE*SAMPLE; j++) {
+		if (occupancy[j]) {
+		    cairo_rectangle (cr,
+				     (j % SAMPLE + xs) / (double) SAMPLE,
+				     (j / SAMPLE + ys) / (double) SAMPLE,
+				     1 / (double) SAMPLE,
+				     1 / (double) SAMPLE);
+		}
+	    }
+	    cairo_fill (cr);
+	}
+    }
+
+    free (occupancy);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+static cairo_test_status_t
+triangles (cairo_t *cr, int width, int height)
+{
+    uint8_t *occupancy;
+    int i, j, channel;
+
+    state = 0x12345678;
+    occupancy = xmalloc (SAMPLE*SAMPLE);
+
+    cairo_set_source_rgb (cr, 0.0, 0.0, 0.0);
+    cairo_paint (cr);
+
+    cairo_set_operator (cr, CAIRO_OPERATOR_ADD);
+    for (channel = 0; channel < 3; channel++) {
+	switch (channel) {
+	default:
+	case 0: cairo_set_source_rgb (cr, 1.0, 0.0, 0.0); break;
+	case 1: cairo_set_source_rgb (cr, 0.0, 1.0, 0.0); break;
+	case 2: cairo_set_source_rgb (cr, 0.0, 0.0, 1.0); break;
+	}
+
+	for (i = 0; i < SIZE*SIZE; i++) {
+	    int xs, ys;
+
+	    compute_occupancy (occupancy, SAMPLE*SAMPLE * i / (SIZE * SIZE));
+
+	    xs = i % SIZE * SAMPLE;
+	    ys = i / SIZE * SAMPLE;
+	    for (j = 0; j < SAMPLE*SAMPLE; j++) {
+		if (occupancy[j]) {
+		    int x = j % SAMPLE + xs;
+		    int y = j / SAMPLE + ys;
+		    cairo_move_to (cr, x / (double) SAMPLE, y / (double) SAMPLE);
+		    cairo_line_to (cr, (x+1) / (double) SAMPLE, (y+1) / (double) SAMPLE);
+		    cairo_line_to (cr, (x+1) / (double) SAMPLE, y / (double) SAMPLE);
+		    cairo_close_path (cr);
+		}
+	    }
+	    cairo_fill (cr);
+	}
+    }
+
+    free (occupancy);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+CAIRO_TEST (partial_coverage_rectangles,
+	    "Check the fidelity of the rasterisation.",
+	    "coverage raster", /* keywords */
+	    "raster", /* requirements */
+	    SIZE, SIZE,
+	    NULL, rectangles)
+
+CAIRO_TEST (partial_coverage_triangles,
+	    "Check the fidelity of the rasterisation.",
+	    "coverage raster", /* keywords */
+	    "raster", /* requirements */
+	    SIZE, SIZE,
+	    NULL, triangles)
+
+CAIRO_TEST (partial_coverage_reference,
+	    "Check the fidelity of this test.",
+	    "coverage raster", /* keywords */
+	    "raster", /* requirements */
+	    SIZE, SIZE,
+	    NULL, reference)