Pixelated layer on image in ios - ios

Question

I need to add pixelated rectangular layer on UIImage which can be undo. Just like this..
I used this code but its not doing the same thing as i need
CALayer *maskLayer = [CALayer layer];
CALayer *mosaicLayer = [CALayer layer];
// Mask image ends with 0.15 opacity on both sides. Set the background color of the layer
// to the same value so the layer can extend the mask image.
mosaicLayer.contents = (id)[img CGImage];
mosaicLayer.frame = CGRectMake(0,0, img.size.width, img.size.height);
UIImage *maskImg = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:#"mask" ofType:#"png"]];
maskLayer.contents = (id)[maskImg CGImage];
maskLayer.frame = CGRectMake(100,150, maskImg.size.width, maskImg.size.height);
mosaicLayer.mask = maskLayer;
[imageView.layer addSublayer:mosaicLayer];
UIGraphicsBeginImageContext(imageView.layer.bounds.size);
[imageView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *saver = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
is there any built-in filter by apple for iOS? Please guide me Thanks

Answer 1

You can use GPUImage's GPUImagePixellateFilter https://github.com/BradLarson/GPUImage/blob/8811da388aed22e04ed54ca9a5a76791eeb40551/framework/Source/GPUImagePixellateFilter.h

Answer 2

We can use GPUImage framework but lot better is to use iOS own filters. easy coding :)
- (UIImage *)applyCIPixelateFilter:(UIImage*)fromImage withScale:(double)scale
{
/*
Makes an image blocky by mapping the image to colored squares whose color is defined by the replaced pixels.
Parameters
inputImage: A CIImage object whose display name is Image.
inputCenter: A CIVector object whose attribute type is CIAttributeTypePosition and whose display name is Center.
Default value: [150 150]
inputScale: An NSNumber object whose attribute type is CIAttributeTypeDistance and whose display name is Scale.
Default value: 8.00
*/
CIContext *context = [CIContext contextWithOptions:nil];
CIFilter *filter= [CIFilter filterWithName:#"CIPixellate"];
CIImage *inputImage = [[CIImage alloc] initWithImage:fromImage];
CIVector *vector = [CIVector vectorWithX:fromImage.size.width /2.0f Y:fromImage.size.height /2.0f];
[filter setDefaults];
[filter setValue:vector forKey:#"inputCenter"];
[filter setValue:[NSNumber numberWithDouble:scale] forKey:#"inputScale"];
[filter setValue:inputImage forKey:#"inputImage"];
CGImageRef cgiimage = [context createCGImage:filter.outputImage fromRect:filter.outputImage.extent];
UIImage *newImage = [UIImage imageWithCGImage:cgiimage scale:1.0f orientation:fromImage.imageOrientation];
CGImageRelease(cgiimage);
return newImage;
}