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POHow to cut a hole in UIImage?
 

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  1. POHow to cut a hole in UIImage?
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    <p>using a mask. mask is a usual black png image with transparent background. Here i create a usual white image with a size of a base image. Then added mask on a white image on the needed position. Then i invert mask because method maskImage:WithMask remove only black areas. So i have a base image with a hole which looks like a mask. On the position i need. And it works. But when i try to cut one more hole on the other position - it crashes. Please tell me: there's my fault?</p> <p>here is main method:</p> <pre><code>- (UIImage *)makeAHoleIn:(UIImage *)baseImage withAMask:(UIImage *)mask onPosition:(CGPoint)position { UIImage *whiteImage = [self createWhiteImageWithSize:baseImage.size]; UIImage *goodmask = [self mergeImage:whiteImage with:mask onPosition:position]; UIImage *finalmask = [self invertImage:goodmask]; UIImage *finalImage = [self maskImage:baseImage withMask:finalmask]; return finalImage; } </code></pre> <p>and other methods:</p> <pre><code>- (UIImage *)createWhiteImageWithSize:(CGSize)size { UIGraphicsBeginImageContext(size); CGContextSetRGBFillColor(UIGraphicsGetCurrentContext(), 255, 255, 255, 1); CGContextFillRect (UIGraphicsGetCurrentContext(), CGRectMake (0, 0, size.width, size.height)); UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return resultImage; } - (UIImage *) mergeImage:(UIImage *)backImage with:(UIImage *)frontImage onPosition:(CGPoint)position { CGSize finalSize = backImage.size; CGSize impositionSize = frontImage.size; UIGraphicsBeginImageContext(finalSize); [backImage drawInRect:CGRectMake(0, 0, finalSize.width, finalSize.height)]; [frontImage drawInRect:CGRectMake(position.x, position.y, impositionSize.width, impositionSize.height)]; UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return resultImage; } - (UIImage*) maskImage:(UIImage *)image withMask:(UIImage *)maskImage { 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); return [UIImage imageWithCGImage:masked]; } - (UIImage *)invertImage:(UIImage *)originalImage { UIGraphicsBeginImageContext(originalImage.size); CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeCopy); [originalImage drawInRect:CGRectMake(0, 0, originalImage.size.width, originalImage.size.height)]; CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeDifference); CGContextSetFillColorWithColor(UIGraphicsGetCurrentContext(),[UIColor whiteColor].CGColor); CGContextFillRect(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, originalImage.size.width, originalImage.size.height)); UIImage *returnImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return returnImage; } </code></pre>
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    1. USlikecatfood
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    1. COwhat line is the app crashing at? what's the error?
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      1. USMike M
    2. CO@MikeM it happens in method maskImage:withMask at line 'CGImageRef masked = CGImageCreateWithMask([image CGImage], mask);' here mask has an adress but masked -value is nill
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    3. COi mean it's 0x0
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