pink halfton

pink halfton

- (NSString *)getFragmentShaderString
{
    NSString *const kFragmentShaderString = SHADER_STRING
    (
     varying highp vec2 textureCoordinate;

     uniform sampler2D inputImageTexture;

     uniform highp float fractionalWidthOfPixel;
     uniform highp float aspectRatio;
     uniform highp float dotScaling;

    const highp vec3 W = vec3(0.2125, 0.7154, 0.0721);
     
     void main()
     {
         highp vec2 sampleDivisor = vec2(fractionalWidthOfPixel, fractionalWidthOfPixel / aspectRatio);

         highp vec2 samplePos = textureCoordinate - mod(textureCoordinate, sampleDivisor) + 0.5 * sampleDivisor;
         
         highp vec2 textureCoordinateToUse = vec2(textureCoordinate.x, (textureCoordinate.y * aspectRatio + 0.5 - 0.5 * aspectRatio));
         highp vec2 adjustedSamplePos = vec2(samplePos.x, (samplePos.y * aspectRatio + 0.5 - 0.5 * aspectRatio));
         highp float distanceFromSamplePoint = distance(adjustedSamplePos, textureCoordinateToUse);
         lowp float checkForPresenceWithinDot = step(distanceFromSamplePoint, (fractionalWidthOfPixel * 0.5) * dotScaling);

         highp vec3 dispColor = vec4(texture2D(inputImageTexture, samplePos ).rgb * checkForPresenceWithinDot, 1.0).rgb;

         highp float gray = step(0.45,dot(dispColor, W));

         lowp vec4 colorToDisplay = vec4(1.0, 1.0, 1.0, 1.0);

         if (gray < 1.00)
         {
             colorToDisplay = vec4(0.58, 0.00, 0.83, 1.0);
         }

         highp float gray2 = step(0.25,dot(dispColor, W));

         if (gray2 < 1.00)
         {
             colorToDisplay = vec4(1.00, 0.41, 0.71, 1.0);
         }
         
         gl_FragColor = colorToDisplay;
     }

     );

    return kFragmentShaderString;
}