41 lines
1.1 KiB
GLSL
41 lines
1.1 KiB
GLSL
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uniform sampler2D inputTexture;
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uniform float hueAdjust;
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void main ()
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{
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const vec4 kRGBToYPrime = vec4 (0.299, 0.587, 0.114, 0.0);
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const vec4 kRGBToI = vec4 (0.596, -0.275, -0.321, 0.0);
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const vec4 kRGBToQ = vec4 (0.212, -0.523, 0.311, 0.0);
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const vec4 kYIQToR = vec4 (1.0, 0.956, 0.621, 0.0);
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const vec4 kYIQToG = vec4 (1.0, -0.272, -0.647, 0.0);
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const vec4 kYIQToB = vec4 (1.0, -1.107, 1.704, 0.0);
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// Sample the input pixel
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vec4 color = texture2D (inputTexture, gl_TexCoord [ 0 ].xy);
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// Convert to YIQ
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float YPrime = dot (color, kRGBToYPrime);
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float I = dot (color, kRGBToI);
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float Q = dot (color, kRGBToQ);
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// Calculate the hue and chroma
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float hue = atan (Q, I);
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float chroma = sqrt (I * I + Q * Q);
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// Make the user's adjustments
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hue += hueAdjust;
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// Convert back to YIQ
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Q = chroma * sin (hue);
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I = chroma * cos (hue);
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// Convert back to RGB
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vec4 yIQ = vec4 (YPrime, I, Q, 0.0);
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color.r = dot (yIQ, kYIQToR);
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color.g = dot (yIQ, kYIQToG);
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color.b = dot (yIQ, kYIQToB);
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// Save the result
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gl_FragColor = color;
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}
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