#extension GL_OES_EGL_image_external : require

precision highp float;

varying highp vec2 textureCoordinate;

uniform samplerExternalOES inputImageTexture;
uniform sampler2D curve; 

vec3 rgb2hsv(vec3 c)
{ 
    vec4 K = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0); 
    vec4 p = mix(vec4(c.bg, K.wz), vec4(c.gb, K.xy), step(c.b, c.g)); 
    vec4 q = mix(vec4(p.xyw, c.r), vec4(c.r, p.yzx), step(p.x, c.r)); 
    
    float d = q.x - min(q.w, q.y); 
    float e = 1.0e-10; 
    return vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x); 
} 

vec3 hsv2rgb(vec3 c) { 
    vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0); 
    vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www); 
    return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y); 
} 

void main() {
    float GreyVal; 
    lowp vec4 textureColor; 
    lowp vec4 textureColorOri; 
    float xCoordinate = textureCoordinate.x; 
    float yCoordinate = textureCoordinate.y; 

    highp float redCurveValue; 
    highp float greenCurveValue; 
    highp float blueCurveValue; 
    textureColor = texture2D( inputImageTexture, vec2(xCoordinate, yCoordinate)); 
    // step1 curve 
    redCurveValue = texture2D(curve, vec2(textureColor.r, 0.0)).r; 
    greenCurveValue = texture2D(curve, vec2(textureColor.g, 0.0)).g; 
    blueCurveValue = texture2D(curve, vec2(textureColor.b, 0.0)).b; 


    //textureColor = vec4(redCurveValue, greenCurveValue, blueCurveValue, 1.0); 
    vec3 tColor = vec3(redCurveValue, greenCurveValue, blueCurveValue); 
    tColor = rgb2hsv(tColor);

    tColor.g = tColor.g * 1.2; 

    float dStrength = 1.0; 
    float dSatStrength = 0.3; 

    float dGap = 0.0; 

    if( tColor.r >= 0.0 && tColor.r < 0.417) 
    { 
        tColor.g = tColor.g + (tColor.g * dSatStrength); 
    } 
    else if( tColor.r > 0.958 && tColor.r <= 1.0) 
    { 
        tColor.g = tColor.g + (tColor.g * dSatStrength);
    } 
    else if( tColor.r >= 0.875 && tColor.r <= 0.958) 
    { 
        dGap = abs(tColor.r - 0.875); 
        dStrength = (dGap / 0.0833); 
        
        tColor.g = tColor.g + (tColor.g * dSatStrength * dStrength);
    } 
    else if( tColor.r >= 0.0417 && tColor.r <= 0.125) 
    { 
        dGap = abs(tColor.r - 0.125); 
        dStrength = (dGap / 0.0833);

        tColor.g = tColor.g + (tColor.g * dSatStrength * dStrength); 
    } 

    tColor = hsv2rgb(tColor); 
    tColor = clamp(tColor, 0.0, 1.0); 

    redCurveValue = texture2D(curve, vec2(tColor.r, 1.0)).r; 
    greenCurveValue = texture2D(curve, vec2(tColor.g, 1.0)).r; 
    blueCurveValue = texture2D(curve, vec2(tColor.b, 1.0)).r; 

    redCurveValue = texture2D(curve, vec2(redCurveValue, 1.0)).g; 
    greenCurveValue = texture2D(curve, vec2(greenCurveValue, 1.0)).g; 
    blueCurveValue = texture2D(curve, vec2(blueCurveValue, 1.0)).g; 

    textureColor = vec4(redCurveValue, greenCurveValue, blueCurveValue, 1.0); 

    gl_FragColor = vec4(textureColor.r, textureColor.g, textureColor.b, 1.0); 
}