9f1cb386
 dangge
auto package
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#ifdef GL_ES
precision mediump float;
#endif
varying vec2 v_texCoord;
uniform float u_hueAdjust;
const vec4 kRGBToYPrime = vec4 (0.299, 0.587, 0.114, 0.0);
const vec4 kRGBToI = vec4 (0.595716, -0.274453, -0.321263, 0.0);
const vec4 kRGBToQ = vec4 (0.211456, -0.522591, 0.31135, 0.0);
const vec4 kYIQToR = vec4 (1.0, 0.9563, 0.6210, 0.0);
const vec4 kYIQToG = vec4 (1.0, -0.2721, -0.6474, 0.0);
const vec4 kYIQToB = vec4 (1.0, -1.1070, 1.7046, 0.0);
void main ()
{
// Sample the input pixel
vec4 color = texture2D(CC_Texture0, v_texCoord);
// Convert to YIQ
float YPrime = dot (color, kRGBToYPrime);
float I = dot (color, kRGBToI);
float Q = dot (color, kRGBToQ);
// Calculate the hue and chroma
float hue = atan (Q, I);
float chroma = sqrt (I * I + Q * Q);
// Make the user's adjustments
hue += (-u_hueAdjust); //why negative rotation?
// Convert back to YIQ
Q = chroma * sin (hue);
I = chroma * cos (hue);
// Convert back to RGB
vec4 yIQ = vec4 (YPrime, I, Q, 0.0);
color.r = dot (yIQ, kYIQToR);
color.g = dot (yIQ, kYIQToG);
color.b = dot (yIQ, kYIQToB);
// Save the result
gl_FragColor = color;
}
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