1 files changed, 30 insertions, 0 deletions
diff --git a/vcl/opengl/shaders/diffTextureFragmentShader.glsl b/vcl/opengl/shaders/diffTextureFragmentShader.glsl
new file mode 100644
index 000000000..8c50ddf98
--- /dev/null
+++ b/vcl/opengl/shaders/diffTextureFragmentShader.glsl
@@ -0,0 +1,30 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#version 130
+
+/*precision mediump float;*/
+varying vec2 tex_coord;
+varying vec2 mask_coord;
+uniform sampler2D texture; /* white background */
+uniform sampler2D mask;    /* black background */
+
+void main()
+{
+    float alpha;
+    vec4 texel0, texel1;
+    texel0 = texture2D(texture, tex_coord);
+    texel1 = texture2D(mask, mask_coord);
+    alpha = 1.0 - abs(texel0.r - texel1.r);
+    if(alpha > 0.0)
+        gl_FragColor = texel1 / alpha;
+    gl_FragColor.a = alpha;
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */