laplacian: precalculate coordinates

Precalculate coordinates to avoid unneeded texture indirections.
Now laplacian works on i915.

1 files changed, 29 insertions, 24 deletions

diff --git a/gst/gl/gstglfilterlaplacian.c b/gst/gl/gstglfilterlaplacian.c
index c6ebe0f..79de5bb 100644
--- a/gst/gl/gstglfilterlaplacian.c
+++ b/gst/gl/gstglfilterlaplacian.c
@@ -1,6 +1,6 @@
 /*
  * GStreamer
- * Copyright (C) 2008 Filippo Argiolas <filippo.argiolas@gmail.com>
+ * Copyright (C) 2008-2010 Filippo Argiolas <filippo.argiolas@gmail.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ -65,30 +65,35 @@ static void gst_gl_filter_laplacian_callback (gint width, gint height,
     guint texture, gpointer stuff);
 
 /* *INDENT-OFF* */
+
+/* This filter is meant as a demo of gst-plugins-gl + glsl
+   capabilities. So I'm keeping this shader readable enough. If and
+   when this shader will be used in production be careful to hard code
+   kernel into the shader and remove unneeded zero multiplications in
+   the convolution */
 static const gchar *convolution_fragment_source =
-    "#extension GL_ARB_texture_rectangle : enable\n"
-    "uniform sampler2DRect tex;"
-    "uniform float kernel[9];"
-    "void main () {"
-    "  vec2 offset[9];"
-    "  offset[0] = vec2(-1.0,-1.0);"
-    "  offset[1] = vec2( 0.0,-1.0);"
-    "  offset[2] = vec2( 1.0,-1.0);"
-    "  offset[3] = vec2(-1.0, 0.0);"
-    "  offset[4] = vec2( 0.0, 0.0);"
-    "  offset[5] = vec2( 1.0, 0.0);"
-    "  offset[6] = vec2(-1.0, 1.0);"
-    "  offset[7] = vec2( 0.0, 1.0);"
-    "  offset[8] = vec2( 1.0, 1.0);"
-    "  vec2 texturecoord = gl_TexCoord[0].st;"
-    "  int i;"
-    "  vec4 sum = vec4 (0.0);"
-    "  for (i = 0; i < 9; i++) { "
-    "    vec4 neighbor = texture2DRect(tex, texturecoord + vec2(offset[i]));"
-    "    sum += neighbor * kernel[i];"
-    "  }"
-    "  gl_FragColor = sum;"
-    "}";
+  "#extension GL_ARB_texture_rectangle : enable\n"
+  "uniform sampler2DRect tex;"
+  "uniform float kernel[9];"
+  "void main () {"
+  "  vec2 texturecoord[9];"
+  "  texturecoord[4] = gl_TexCoord[0].st;"                /*  0  0 */
+  "  texturecoord[5] = texturecoord[4] + vec2(1.0, 0.0);" /*  1  0 */
+  "  texturecoord[2] = texturecoord[5] - vec2(0.0, 1.0);" /*  1 -1 */
+  "  texturecoord[1] = texturecoord[2] - vec2(1.0, 0.0);" /*  0 -1 */
+  "  texturecoord[0] = texturecoord[1] - vec2(1.0, 0.0);" /* -1 -1 */
+  "  texturecoord[3] = texturecoord[0] + vec2(0.0, 1.0);" /* -1  0 */
+  "  texturecoord[6] = texturecoord[3] + vec2(0.0, 1.0);" /* -1  1 */
+  "  texturecoord[7] = texturecoord[6] + vec2(1.0, 0.0);" /*  0  1 */
+  "  texturecoord[8] = texturecoord[7] + vec2(1.0, 0.0);" /*  1  1 */
+  "  int i;"
+  "  vec4 sum = vec4 (0.0);"
+  "  for (i = 0; i < 9; i++) { "
+  "    vec4 neighbor = texture2DRect(tex, texturecoord[i]);"
+  "    sum += neighbor * kernel[i];"
+  "  }"
+  "  gl_FragColor = sum;"
+  "}";
 /* *INDENT-ON* */
 
 static void