Question

I am using Core Image and would like to produce a black and white effect on the chosen image.

Ideally I would like to have access to the same sort of options that are available on Photoshop i.e. Reds, Cyan, Greens, Blues and Magenta. The goal being to create different types of the black and white effect.

Does anyone know what filter would be best to manipulate these sort of options? If not does anyone know of a good approach to creating the black and white effect using other filters?

Thanks

Oliver

Answer 1

- (UIImage *)imageBlackAndWhite
{
    CIImage *beginImage = [CIImage imageWithCGImage:self.CGImage];

    CIImage *blackAndWhite = [CIFilter filterWithName:@"CIColorControls" keysAndValues:kCIInputImageKey, beginImage, @"inputBrightness", [NSNumber numberWithFloat:0.0], @"inputContrast", [NSNumber numberWithFloat:1.1], @"inputSaturation", [NSNumber numberWithFloat:0.0], nil].outputImage;
    CIImage *output = [CIFilter filterWithName:@"CIExposureAdjust" keysAndValues:kCIInputImageKey, blackAndWhite, @"inputEV", [NSNumber numberWithFloat:0.7], nil].outputImage; 

    CIContext *context = [CIContext contextWithOptions:nil];
    CGImageRef cgiimage = [context createCGImage:output fromRect:output.extent];
    //UIImage *newImage = [UIImage imageWithCGImage:cgiimage];
    UIImage *newImage = [UIImage imageWithCGImage:cgiimage scale:image.scale orientation:image.imageOrientation];
    CGImageRelease(cgiimage);

    return newImage;
}

Upd.: For iOS6 there is CIColorMonochrome filter, but I played with it and found it not so good as mine.