* Merged chroma key feature, but removed unsupported parameters and color names....

[casparcg] / accelerator / ogl / image / blending_glsl.h

diff --git a/accelerator/ogl/image/blending_glsl.h b/accelerator/ogl/image/blending_glsl.h
index 2d5635de8185959cb5cdfcc0b71fcb25762e3196..42e95f37f83a9775a76369955d587ce49dc3c459 100644 (file)
--- a/accelerator/ogl/image/blending_glsl.h
+++ b/accelerator/ogl/image/blending_glsl.h
@@ -267,3 +267,54 @@ static std::string get_blend_glsl()
 
        return glsl;
 }
+
+static std::string get_chroma_glsl()
+{
+       static std::string glsl = R"shader(
+               // Chroma keying
+               // Author: Tim Eves <timseves@googlemail.com>
+               //
+               // This implements the Chroma key algorithm described in the paper:
+               //      'Software Chroma Keying in an Imersive Virtual Environment'
+               //      by F. van den Bergh & V. Lalioti
+               // but as a pixel shader algorithm.
+               //
+
+               float       chroma_blend_w = chroma_blend.y - chroma_blend.x;
+               const vec4  grey_xfer  = vec4(0.3, 0.59, 0.11, 0.0);
+
+               float fma(float a, float b, float c) { return a*b + c; }
+
+               // This allows us to implement the paper's alphaMap curve in software
+               // rather than a largeish array
+               float alpha_map(float d)
+               {
+                   return 1.0-smoothstep(chroma_blend.x, chroma_blend.y, d);
+               }
+
+               vec4 supress_spill(vec4 c, float d)
+               {
+                   float ds = smoothstep(chroma_spill, 1.0, d/chroma_blend.y);
+                   float gl = dot(grey_xfer, c);
+                   return mix(c, vec4(vec3(gl*gl), gl), ds);
+               }
+
+               // Key on green
+               vec4 ChromaOnGreen(vec4 c)
+               {
+                   float d = fma(2.0, c.g, -c.r - c.b)/2.0;
+                   c *= alpha_map(d);
+                   return supress_spill(c, d);
+               }
+
+               //Key on blue
+               vec4 ChromaOnBlue(vec4 c)
+               {
+                   float d = fma(2.0, c.b, -c.r - c.g)/2.0;
+                   c *= alpha_map(d);
+                   return supress_spill(c, d);
+               }
+       )shader";
+
+       return glsl;
+}