Add new test of filter reduction from BILINEAR to NEAREST

This new test tests a bunch of bilinear downscalings, where many have
a transformation such that the BILINEAR filter can be reduced to
NEAREST (and many don't).

A CRC32 is computed for all the resulting images and compared to a
known-good value for both 4-bit and 7-bit interpolation.

V2: Remove leftover comment, some minor formatting fixes, use a
timestamp as the PRNG seed.

Signed-off-by: Søren Sandmann <soren.sandmann@gmail.com>
Reviewed-by: Bill Spitzak <spitzak@gmail.com>

2 files changed, 113 insertions, 0 deletions

diff --git a/test/Makefile.sources b/test/Makefile.sources
index 5d55e67..0a56231 100644
--- a/test/Makefile.sources
+++ b/test/Makefile.sources
@@ -21,6 +21,7 @@ TESTPROGRAMS =			      \
 	gradient-crash-test	      \
 	pixel-test		      \
 	matrix-test		      \
+	filter-reduction-test         \
 	composite-traps-test	      \
 	region-contains-test	      \
 	glyph-test		      \
diff --git a/test/filter-reduction-test.c b/test/filter-reduction-test.c
new file mode 100644
index 0000000..705fa4b
--- /dev/null
+++ b/test/filter-reduction-test.c
@@ -0,0 +1,112 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include "utils.h"
+
+static const pixman_fixed_t entries[] =
+{
+    pixman_double_to_fixed (-1.0),
+    pixman_double_to_fixed (-0.5),
+    pixman_double_to_fixed (-1/3.0),
+    pixman_double_to_fixed (0.0),
+    pixman_double_to_fixed (0.5),
+    pixman_double_to_fixed (1.0),
+    pixman_double_to_fixed (1.5),
+    pixman_double_to_fixed (2.0),
+    pixman_double_to_fixed (3.0),
+};
+
+#define SIZE 12
+
+static uint32_t
+test_scale (const pixman_transform_t *xform, uint32_t crc)
+{
+    uint32_t *srcbuf, *dstbuf;
+    pixman_image_t *src, *dest;
+
+    srcbuf = malloc (SIZE * SIZE * 4);
+    prng_randmemset (srcbuf, SIZE * SIZE * 4, 0);
+    src = pixman_image_create_bits (
+	PIXMAN_a8r8g8b8, SIZE, SIZE, srcbuf, SIZE * 4);
+
+    dstbuf = malloc (SIZE * SIZE * 4);
+    prng_randmemset (dstbuf, SIZE * SIZE * 4, 0);
+    dest = pixman_image_create_bits (
+	PIXMAN_a8r8g8b8, SIZE, SIZE, dstbuf, SIZE * 4);
+
+    pixman_image_set_transform (src, xform);
+    pixman_image_set_repeat (src, PIXMAN_REPEAT_NORMAL);
+    pixman_image_set_filter (src, PIXMAN_FILTER_BILINEAR, NULL, 0);
+
+    image_endian_swap (src);
+    image_endian_swap (dest);
+
+    pixman_image_composite (PIXMAN_OP_SRC,
+			    src, NULL, dest,
+			    0, 0, 0, 0, 0, 0,
+			    SIZE, SIZE);
+
+    crc = compute_crc32_for_image (crc, dest);
+
+    pixman_image_unref (src);
+    pixman_image_unref (dest);
+
+    free (srcbuf);
+    free (dstbuf);
+
+    return crc;
+}
+
+#if BILINEAR_INTERPOLATION_BITS == 7
+#define CHECKSUM 0x02169677
+#elif BILINEAR_INTERPOLATION_BITS == 4
+#define CHECKSUM 0xE44B29AC
+#else
+#define CHECKSUM 0x00000000
+#endif
+
+int
+main (int argc, const char *argv[])
+{
+    const pixman_fixed_t *end = entries + ARRAY_LENGTH (entries);
+    const pixman_fixed_t *t0, *t1, *t2, *t3, *t4, *t5;
+    uint32_t crc = 0;
+
+    prng_srand (0x56EA1DBD);
+
+    for (t0 = entries; t0 < end; ++t0)
+    {
+	for (t1 = entries; t1 < end; ++t1)
+	{
+	    for (t2 = entries; t2 < end; ++t2)
+	    {
+		for (t3 = entries; t3 < end; ++t3)
+		{
+		    for (t4 = entries; t4 < end; ++t4)
+		    {
+			for (t5 = entries; t5 < end; ++t5)
+			{
+			    pixman_transform_t xform = {
+				{ { *t0, *t1, *t2 },
+				  { *t3, *t4, *t5 },
+				  { 0, 0, pixman_fixed_1 } }
+			    };
+
+			    crc = test_scale (&xform, crc);
+			}
+		    }
+		}
+	    }
+	}
+    }
+
+    if (crc != CHECKSUM)
+    {
+	printf ("filter-reduction-test failed! (checksum=0x%08X, expected 0x%08X)\n", crc, CHECKSUM);
+	return 1;
+    }
+    else
+    {
+	printf ("filter-reduction-test passed (checksum=0x%08X)\n", crc);
+	return 0;
+    }
+}