Split tone effect using core image filters?
| 1 0 0 -0.5 |   | 1.5 0.0 0    0 |   | 1 0 0 0.5 |
| 0 1 0 -0.5 | + | 0   1.5 0    0 | + | 0 1 0 0.5 |
| 0 0 1 -0.5 |   | 0   0.0 0.66 0 |   | 0 0 1 0.5 |
| 0 0 0  1.0 |   | 0   0.0 0.0 1.0|   | 0 0 0 1.0 |

CIFilter *lightDark = [CIFilter filterWithName:@"CIFalseColor"
                                       keysAndValues: @"inputImage", helper.ciImage, nil];
[lightDark setDefaults];
CIColor *myBlue = [CIColor colorWithRed:0.0 green:0.0 blue:0.6 alpha:0.5];
CIColor *myRed = [CIColor colorWithRed:1.0 green:0.8 blue:0.0 alpha:0.5];

[lightDark setValue:myBlue forKey:@"inputColor0"];
[lightDark setValue:myRed forKey:@"inputColor1"];
CIImage *mappedImage = [lightDark valueForKey:kCIOutputImageKey];

CIFilter *screenBlend = [CIFilter filterWithName:@"CIScreenBlendMode" keysAndValues: @"inputImage", mappedImage, @"inputBackgroundImage", helper.ciImage, nil];
CIImage *finalImage = [screenBlend valueForKey:kCIOutputImageKey];

if (finalImage) imageView.image = [UIImage imageWithCIImage:finalImage orientation:orientation];
else NSLog(@"Missing our image");