[Piglit] [PATCH 1/9] util: Add probe function to test for two colors.

[Fabian Bieler]

Add piglit_probe_rect_two_rgba.
This probe functions tests that all pixels in a rectangle are one of two
specified colors.

This is useful to test that two draw operations behave identically:
To use it clear the framebuffer, enable blending and make each draw operation
paint one color channel.
Then call piglit_probe_rect_two_rgba to determine that the framebuffer is either
the clear color or the combined color of both operations.
---
 tests/util/piglit-util-gl-common.c | 51 ++++++++++++++++++++++++++++++++++++++
 tests/util/piglit-util-gl-common.h |  2 ++
 2 files changed, 53 insertions(+)

diff --git a/tests/util/piglit-util-gl-common.c b/tests/util/piglit-util-gl-common.c
index 82ae820..0a01d5c 100644
--- a/tests/util/piglit-util-gl-common.c
+++ b/tests/util/piglit-util-gl-common.c
@@ -440,6 +440,57 @@ piglit_probe_rect_halves_equal_rgba(int x, int y, int w, int h)
 
 
 /**
+ * Checks that all pixels in a rectangular part of the framebuffer are one of
+ * two colors.
+ * \param  x, y, w, h the rectangle to test
+ * \param  expected1, expected2 the two expected colors
+ * \return 1 if all pixels in the rectangle are one of the expected colors,
+ *         0 otherwise.
+ */
+int
+piglit_probe_rect_two_rgba(int x, int y, int w, int h,
+			   const float* expected1, const float* expected2)
+{
+	int i, j, p;
+	GLubyte *probe;
+	GLubyte *pixels = malloc(w*h*4*sizeof(GLubyte));
+
+	glReadPixels(x, y, w, h, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
+
+	for (j = 0; j < h; j++) {
+		for (i = 0; i < w; i++) {
+			probe = &pixels[(j*w+i)*4];
+
+			for (p = 0; p < 4; ++p) {
+				if ((fabs(probe[p]/255.0 - expected1[p]) <
+				     piglit_tolerance[p]) ||
+				    (fabs(probe[p]/255.0 - expected2[p]) <
+				     piglit_tolerance[p]))
+					continue;
+
+				printf("Probe color at (%i,%i)\n", x+i, y+j);
+				printf("  Expected: %f %f %f %f\n",
+				       expected1[0], expected1[1],
+				       expected1[2], expected1[3]);
+				printf("        or: %f %f %f %f\n",
+				       expected2[0], expected2[1],
+				       expected2[2], expected2[3]);
+				printf("  Observed: %f %f %f %f\n",
+				       probe[0]/255.0, probe[1]/255.0,
+				       probe[2]/255.0, probe[3]/255.0);
+
+				free(pixels);
+				return 0;
+			}
+		}
+	}
+
+	free(pixels);
+	return 1;
+}
+
+
+/**
  * Return block size info for a specific texture compression format.
  * \param  bw returns the block width, in pixels
  * \param  bh returns the block height, in pixels
diff --git a/tests/util/piglit-util-gl-common.h b/tests/util/piglit-util-gl-common.h
index aa21391..02eeae7 100644
--- a/tests/util/piglit-util-gl-common.h
+++ b/tests/util/piglit-util-gl-common.h
@@ -145,6 +145,8 @@ int piglit_probe_rect_depth(int x, int y, int w, int h, float expected);
 int piglit_probe_pixel_stencil(int x, int y, unsigned expected);
 int piglit_probe_rect_stencil(int x, int y, int w, int h, unsigned expected);
 int piglit_probe_rect_halves_equal_rgba(int x, int y, int w, int h);
+int piglit_probe_rect_two_rgba(int x, int y, int w, int h,
+			       const float* expected1, const float* expected2);
 
 int piglit_use_fragment_program(void);
 int piglit_use_vertex_program(void);
-- 
1.8.1.2