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copied!<p>I'm pretty sure you can't define a transparency when creating UIImages like this - you could mask your UIImageView which uses the image though.</p> <p>Something like the following functions allow for this type of operation:</p> <pre><code>// handles img masking operation CGImageRef CopyImageAndAddAlphaChannel(CGImageRef sourceImage) { CGImageRef retVal = NULL; size_t width = CGImageGetWidth(sourceImage); size_t height = CGImageGetHeight(sourceImage); CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); CGContextRef offscreenContext = CGBitmapContextCreate(NULL, width, height, 8, 0, colorSpace, kCGImageAlphaPremultipliedFirst); if (offscreenContext != NULL) { CGContextDrawImage(offscreenContext, CGRectMake(0, 0, width, height), sourceImage); retVal = CGBitmapContextCreateImage(offscreenContext); CGContextRelease(offscreenContext); } CGColorSpaceRelease(colorSpace); return retVal; } // png masks can mask png, gif or jpg... - (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 sourceImage = [image CGImage]; CGImageRef imageWithAlpha = sourceImage; //add alpha channel for images that don't have one (ie GIF, JPEG, etc...) //this however has a computational cost if ((CGImageGetAlphaInfo(sourceImage) == kCGImageAlphaNone) || (CGImageGetAlphaInfo(sourceImage) == kCGImageAlphaNoneSkipFirst)) { imageWithAlpha = CopyImageAndAddAlphaChannel(sourceImage); } CGImageRef masked = CGImageCreateWithMask(imageWithAlpha, mask); CGImageRelease(mask); //release imageWithAlpha if it was created by CopyImageAndAddAlphaChannel if (sourceImage != imageWithAlpha) { CGImageRelease(imageWithAlpha); } UIImage* retImage = [UIImage imageWithCGImage:masked]; CGImageRelease(masked); return retImage; } </code></pre> <p>You can than call it like this:</p> <pre><code>UIImage *imgMasked = [self maskImage:[UIImage imageNamed:@"full_image.png"] withMask:[UIImage imageNamed:@"masked_image.png"]]; </code></pre> <p>masked_image.png needs to be an alpha channeled image which will cut out your black bg.</p>

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