[Pixman] [PATCH 2/5] demos: Add linear-gradient demo program

[Søren Sandmann]

From: Søren Sandmann Pedersen <ssp at redhat.com>

This program displays a linear gradient from blue to yellow. Due to
limited precision in pixman-gradient-walker.c, it currently has some
ugly artefacts that gives it a 'brushed metal' appearance.
---
 demos/Makefile.am       |    2 +
 demos/linear-gradient.c |   50 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 0 deletions(-)
 create mode 100644 demos/linear-gradient.c

diff --git a/demos/Makefile.am b/demos/Makefile.am
index 5f53407..9be9ab6 100644
--- a/demos/Makefile.am
+++ b/demos/Makefile.am
@@ -15,6 +15,7 @@ DEMOS =				\
 	composite-test		\
 	gradient-test		\
 	radial-test		\
+	linear-gradient		\
 	conical-test		\
 	alpha-test		\
 	screen-test		\
@@ -38,6 +39,7 @@ trap_test_SOURCES = trap-test.c $(GTK_UTILS)
 screen_test_SOURCES = screen-test.c $(GTK_UTILS)
 convolution_test_SOURCES = convolution-test.c $(GTK_UTILS)
 radial_test_SOURCES = radial-test.c $(GTK_UTILS)
+linear_gradient_SOURCES = linear-gradient.c $(GTK_UTILS)
 conical_test_SOURCES = conical-test.c $(GTK_UTILS)
 tri_test_SOURCES = tri-test.c $(GTK_UTILS)
 checkerboard_SOURCES = checkerboard.c $(GTK_UTILS)
diff --git a/demos/linear-gradient.c b/demos/linear-gradient.c
new file mode 100644
index 0000000..46433a6
--- /dev/null
+++ b/demos/linear-gradient.c
@@ -0,0 +1,50 @@
+#include "../test/utils.h"
+#include "gtk-utils.h"
+
+#define WIDTH 1024
+#define HEIGHT 640
+
+int
+main (int argc, char **argv)
+{
+    pixman_image_t *src_img, *dest_img;
+    pixman_gradient_stop_t stops[] = {
+        { 0x00000, { 0x0000, 0x0000, 0x4444, 0xdddd } },
+        { 0x10000, { 0xeeee, 0xeeee, 0x8888, 0xdddd } },
+#if 0
+        /* These colors make it very obvious that dithering
+         * is useful even for 8-bit gradients
+         */
+	{ 0x00000, { 0x6666, 0x3333, 0x3333, 0xffff } },
+	{ 0x10000, { 0x3333, 0x6666, 0x6666, 0xffff } },
+#endif
+    };
+    pixman_point_fixed_t p1, p2;
+
+    enable_divbyzero_exceptions ();
+
+    dest_img = pixman_image_create_bits (PIXMAN_x8r8g8b8,
+					 WIDTH, HEIGHT,
+					 NULL, 0);
+
+    p1.x = p1.y = 0x0000;
+    p2.x = WIDTH << 16;
+    p2.y = HEIGHT << 16;
+    
+    src_img = pixman_image_create_linear_gradient (&p1, &p2, stops, ARRAY_LENGTH (stops));
+
+    pixman_image_composite32 (PIXMAN_OP_OVER,
+			      src_img,
+			      NULL,
+			      dest_img,
+			      0, 0,
+			      0, 0,
+			      0, 0,
+			      WIDTH, HEIGHT);
+
+    show_image (dest_img);
+
+    pixman_image_unref (dest_img);
+
+    return 0;
+}
-- 
1.7.4