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POCreating mask with CGImageMaskCreate is all black (iphone)
 

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  1. POCreating mask with CGImageMaskCreate is all black (iphone)
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    <p>I'm trying to create an image mask that from a composite of two existing images.</p> <p>First I start with creating the composite which consists of a small image that is the masking image, and a larger image which is the same size as the background:</p> <pre><code>UIImage * BaseTextureImage = [UIImage imageNamed:@"background.png"]; UIImage * MaskImage = [UIImage imageNamed:@"my_mask.jpg"]; UIImage * ShapesBase = [UIImage imageNamed:@"largerimage.jpg"]; UIImage * MaskImageFull; CGSize finalSize = CGSizeMake(480.0, 320.0); UIGraphicsBeginImageContext(finalSize); [ShapesBase drawInRect:CGRectMake(0, 0, 480, 320)]; [MaskImage drawInRect:CGRectMake(150, 50, 250, 250)]; MaskImageFull = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); </code></pre> <p>I can output this UIImage (MaskImageFull) and it looks right, it is a fullsize background size and it is a white background with my mask object in black, in the right place on the screen.</p> <p>I then pass the MaskImageFull UIImage through this:</p> <pre><code>CGImageRef maskRef = [maskImage CGImage]; CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef), CGImageGetHeight(maskRef), CGImageGetBitsPerComponent(maskRef), CGImageGetBitsPerPixel(maskRef), CGImageGetBytesPerRow(maskRef), CGImageGetDataProvider(maskRef), NULL, false); CGImageRef masked = CGImageCreateWithMask([image CGImage], mask); UIImage* retImage= [UIImage imageWithCGImage:masked]; </code></pre> <p>The problem is that the retImage is all black. If I send a pre-made UIImage in as the mask it works fine, it is just when I try to make it from multiple images that it breaks.</p> <p>I thought it was a colorspace thing but couldn't seem to fix it. Any help is much appreciated!</p>
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