gistfile1

if (!compositeToneCurve)
    {
        compositeToneCurve = [CIFilter filterWithName:@"CIToneCurve" keysAndValues:
                              @"inputPoint0", [CIVector vectorWithX:0.0f Y:0.0f],
                              @"inputPoint1", [CIVector vectorWithX:0.184f Y:0.078f],
                              @"inputPoint2", [CIVector vectorWithX:0.427f Y:0.403f],
                              @"inputPoint3", [CIVector vectorWithX:0.741f Y:0.850f],
                              @"inputPoint4", [CIVector vectorWithX:1.0f Y:1.0f],
                              nil];
    }

    [compositeToneCurve setValue:self.inputImage forKey:kCIInputImageKey];

    if (!colorMatrix)
    {
        colorMatrix = [CIFilter filterWithName:@"CIColorMatrix" keysAndValues:
                       @"inputRVector", [CIVector vectorWithX:1 Y:0 Z:0 W:0],
                       @"inputGVector", [CIVector vectorWithX:0 Y:0 Z:0 W:0],
                       @"inputBVector", [CIVector vectorWithX:0 Y:0 Z:0 W:0],
                       @"inputBiasVector", [CIVector vectorWithX:0 Y:1 Z:1 W:0],
                       nil];
    }

    //    [colorMatrix setValue:compositeToneCurve.outputImage forKey:kCIInputImageKey];
    [colorMatrix setValue:self.inputImage forKey:kCIInputImageKey];

    CIFilter *mask = [CIFilter filterWithName:@"CIMinimumComponent" keysAndValues:kCIInputImageKey, colorMatrix.outputImage, nil];

    CIFilter *correction = [CIFilter filterWithName:@"CIColorMatrix" keysAndValues:
                            kCIInputImageKey, self.inputImage,
                            @"inputRVector", [CIVector vectorWithX:1 Y:0 Z:0 W:0],
                            @"inputGVector", [CIVector vectorWithX:0 Y:.5 Z:0 W:0],
                            @"inputBVector", [CIVector vectorWithX:0 Y:0 Z:.5 W:0],
                            @"inputBiasVector", [CIVector vectorWithX:0 Y:1 Z:1 W:0],
                            nil];

    CIFilter *multiplyComposite = [CIFilter filterWithName:@"CIBlendWithMask" keysAndValues:
                                   kCIInputImageKey, correction.outputImage,
                                   kCIInputBackgroundImageKey, self.inputImage,
                                   @"inputMaskImage", mask.outputImage,
                                   nil];
    return multiplyComposite.outputImage;