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copied!<p>If you really want to scale an image, do it, but you should resize it before using it. Resizing it at run time will just lose CPU cycles.</p> <p>This is the category I'm using to scale an image :</p> <p>UIImage+Extra.h </p> <pre><code>@interface UIImage (Extras) - (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize; @end; </code></pre> <p>UIImage+Extra.m</p> <pre><code>@implementation UIImage (Extras) - (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize { UIImage *sourceImage = self; UIImage *newImage = nil; CGSize imageSize = sourceImage.size; CGFloat width = imageSize.width; CGFloat height = imageSize.height; CGFloat targetWidth = targetSize.width; CGFloat targetHeight = targetSize.height; CGFloat scaleFactor = 0.0; CGFloat scaledWidth = targetWidth; CGFloat scaledHeight = targetHeight; CGPoint thumbnailPoint = CGPointMake(0.0,0.0); if (!CGSizeEqualToSize(imageSize, targetSize)) { CGFloat widthFactor = targetWidth / width; CGFloat heightFactor = targetHeight / height; if (widthFactor < heightFactor) scaleFactor = widthFactor; else scaleFactor = heightFactor; scaledWidth = width * scaleFactor; scaledHeight = height * scaleFactor; // center the image if (widthFactor < heightFactor) { thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; } else if (widthFactor > heightFactor) { thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5; } } // this is actually the interesting part: UIGraphicsBeginImageContext(targetSize); CGRect thumbnailRect = CGRectZero; thumbnailRect.origin = thumbnailPoint; thumbnailRect.size.width = scaledWidth; thumbnailRect.size.height = scaledHeight; [sourceImage drawInRect:thumbnailRect]; newImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); if(newImage == nil) NSLog(@"could not scale image"); return newImage ; } @end </code></pre> <p>You can use it to the size you want. Like :</p> <pre><code>[self.itemImageButton setImage:[stretchImage imageByScalingProportionallyToSize:CGSizeMake(20,20)]]; </code></pre>

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