Pods/GPUImage/framework/Source/GPUImageLookupFilter.m
#import "GPUImageLookupFilter.h"

#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageLookupFragmentShaderString = SHADER_STRING
(
 varying highp vec2 textureCoordinate;
 varying highp vec2 textureCoordinate2; // TODO: This is not used
 
 uniform sampler2D inputImageTexture;
 uniform sampler2D inputImageTexture2; // lookup texture
 
 uniform lowp float intensity;

 void main()
 {
     highp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
     
     highp float blueColor = textureColor.b * 63.0;
     
     highp vec2 quad1;
     quad1.y = floor(floor(blueColor) / 8.0);
     quad1.x = floor(blueColor) - (quad1.y * 8.0);
     
     highp vec2 quad2;
     quad2.y = floor(ceil(blueColor) / 8.0);
     quad2.x = ceil(blueColor) - (quad2.y * 8.0);
     
     highp vec2 texPos1;
     texPos1.x = (quad1.x * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * textureColor.r);
     texPos1.y = (quad1.y * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * textureColor.g);
     
     highp vec2 texPos2;
     texPos2.x = (quad2.x * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * textureColor.r);
     texPos2.y = (quad2.y * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * textureColor.g);
     
     lowp vec4 newColor1 = texture2D(inputImageTexture2, texPos1);
     lowp vec4 newColor2 = texture2D(inputImageTexture2, texPos2);
     
     lowp vec4 newColor = mix(newColor1, newColor2, fract(blueColor));
     gl_FragColor = mix(textureColor, vec4(newColor.rgb, textureColor.w), intensity);
 }
);
#else
NSString *const kGPUImageLookupFragmentShaderString = SHADER_STRING
(
 varying vec2 textureCoordinate;
 varying vec2 textureCoordinate2; // TODO: This is not used
 
 uniform sampler2D inputImageTexture;
 uniform sampler2D inputImageTexture2; // lookup texture
 
 uniform float intensity;
 
 void main()
 {
     vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
     
     float blueColor = textureColor.b * 63.0;
     
     vec2 quad1;
     quad1.y = floor(floor(blueColor) / 8.0);
     quad1.x = floor(blueColor) - (quad1.y * 8.0);
     
     vec2 quad2;
     quad2.y = floor(ceil(blueColor) / 8.0);
     quad2.x = ceil(blueColor) - (quad2.y * 8.0);
     
     vec2 texPos1;
     texPos1.x = (quad1.x * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * textureColor.r);
     texPos1.y = (quad1.y * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * textureColor.g);
     
     vec2 texPos2;
     texPos2.x = (quad2.x * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * textureColor.r);
     texPos2.y = (quad2.y * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * textureColor.g);
     
     vec4 newColor1 = texture2D(inputImageTexture2, texPos1);
     vec4 newColor2 = texture2D(inputImageTexture2, texPos2);
     
     vec4 newColor = mix(newColor1, newColor2, fract(blueColor));
     gl_FragColor = mix(textureColor, vec4(newColor.rgb, textureColor.w), intensity);
 }
);
#endif

@implementation GPUImageLookupFilter

@synthesize intensity = _intensity;

#pragma mark -
#pragma mark Initialization and teardown

- (id)init;
{
    intensityUniform = [filterProgram uniformIndex:@"intensity"];
    self.intensity = 1.0f;
    
    if (!(self = [super initWithFragmentShaderFromString:kGPUImageLookupFragmentShaderString]))
    {
		return nil;
    }
    
    return self;
}

#pragma mark -
#pragma mark Accessors

- (void)setIntensity:(CGFloat)intensity
{
    _intensity = intensity;
    
    [self setFloat:_intensity forUniform:intensityUniform program:filterProgram];
}

@end
