Layer.renderInContext ignoring layer.mask?

Question

I am trying to make some UIImages into one single image that I can save in my photo album. But does layer.renderInContext seem to not account for the account?

Current behavior: the photo saves, and I see mosaicLayer, without the maskLayer masking effect.

Expected behavior: the photo is saved, and I see the image in my view, and mosaicLayer is masked on top of it.

I use the following code to mask an image

UIImage *maskImg = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"mask" ofType:@"png"]]; maskLayer = [[UIImageView alloc] initWithImage:maskImg]; maskLayer.multipleTouchEnabled = YES; maskLayer.userInteractionEnabled = YES; UIImageView *mosaicLayer = [[UIImageView alloc] initWithImage:img]; mosaicLayer.contentMode = UIViewContentModeScaleAspectFill; mosaicLayer.frame = [imageView bounds]; mosaicLayer.layer.mask = maskLayer.layer; [imageView addSubview:mosaicLayer]; 

And then I use this code to save my folded image:

 UIGraphicsBeginImageContext(imageView.bounds.size); [imageView.layer renderInContext:UIGraphicsGetCurrentContext()]; UIImage *saver = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); UIImageWriteToSavedPhotosAlbum(saver, self, @selector(image:didFinishSavingWithError:contextInfo:), nil); 

EDIT . Applies the mask correctly.

 -(IBAction) saveImage { UIImage * saver = nil; CGImageRef image = imageView.image.CGImage; size_t cWidth = CGImageGetWidth(image); size_t cHeight = CGImageGetHeight(image); size_t bitsPerComponent = 8; size_t bytesPerRow = 4 * cWidth; //Now we build a Context with those dimensions. CGContextRef context = CGBitmapContextCreate(nil, cWidth, cHeight, bitsPerComponent, bytesPerRow, CGColorSpaceCreateDeviceRGB(), CGImageGetBitmapInfo(image)); //The location where you draw your image on the context is not always the same location you have in your UIView, //this could change and you need to calculate that position according to the scale between you images real size, and the size of the UIImage being show on the UIView. Hence the mod floats... CGContextDrawImage(context, CGRectMake(0, 0, cWidth,cHeight), image); float mod = cWidth/(imageView.frame.size.width); float modTwo = cHeight/(imageView.frame.size.height); //Make the drawing right with coordinate switch CGContextTranslateCTM(context, 0, cHeight); CGContextScaleCTM(context, 1.0, -1.0); CGContextClipToMask(context, CGRectMake(maskLayer.frame.origin.x * mod, maskLayer.frame.origin.y * modTwo, maskLayer.frame.size.width * mod,maskLayer.frame.size.height * modTwo), maskLayer.image.CGImage); //Reverse the coordinate switch CGAffineTransform ctm = CGContextGetCTM(context); ctm = CGAffineTransformInvert(ctm); CGContextConcatCTM(context, ctm); CGContextDrawImage(context, CGRectMake(0, 0, cWidth,cHeight), mosaicLayer.image.CGImage); CGImageRef mergeResult = CGBitmapContextCreateImage(context); saver = [[UIImage alloc] initWithCGImage:mergeResult]; CGContextRelease(context); CGImageRelease(mergeResult); UIImageWriteToSavedPhotosAlbum(saver, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);} 

Answer 1

Documentation for renderInContext: which, among other mask properties, is not supported on Mac OS X 10.5. I suspect this is the same on iOS, even if the documentation doesn't talk about it.

To solve your problem, you may have to draw layers separately in the graphics context, setting the correct mask in the graphics context itself.