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copied!<p>Merely using <code>imageWithCGImage</code> is not sufficient. It will scale, but the result will be blurry and suboptimal whether scaling up or down.</p> <p>If you want to get the aliasing right and get rid of the "jaggies" you need something like this: <a href="http://vocaro.com/trevor/blog/2009/10/12/resize-a-uiimage-the-right-way/" rel="noreferrer">http://vocaro.com/trevor/blog/2009/10/12/resize-a-uiimage-the-right-way/</a>.</p> <p>My working test code looks something like this, which is Trevor's solution with one small adjustment to work with my transparent PNGs:</p> <pre><code>- (UIImage *)resizeImage:(UIImage*)image newSize:(CGSize)newSize { CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height)); CGImageRef imageRef = image.CGImage; UIGraphicsBeginImageContextWithOptions(newSize, NO, 0); CGContextRef context = UIGraphicsGetCurrentContext(); // Set the quality level to use when rescaling CGContextSetInterpolationQuality(context, kCGInterpolationHigh); CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, newSize.height); CGContextConcatCTM(context, flipVertical); // Draw into the context; this scales the image CGContextDrawImage(context, newRect, imageRef); // Get the resized image from the context and a UIImage CGImageRef newImageRef = CGBitmapContextCreateImage(context); UIImage *newImage = [UIImage imageWithCGImage:newImageRef]; CGImageRelease(newImageRef); UIGraphicsEndImageContext(); return newImage; } </code></pre>

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