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POHow to Rotate a UIImage 90 degrees?
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  1. POHow to Rotate a UIImage 90 degrees?
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    copied!<p>I have a <code>UIImage</code> that is <code>UIImageOrientationUp</code> (portrait) that I would like to rotate counter-clockwise by 90 degrees (to landscape). I don't want to use a <code>CGAffineTransform</code>. I want the pixels of the <code>UIImage</code> to actually shift position. I am using a block of code (shown below) originally intended to resize a <code>UIImage</code> to do this. I set a target size as the current size of the <code>UIImage</code> but I get an error:</p> <blockquote> <p>(Error): CGBitmapContextCreate: invalid data bytes/row: should be at least 1708 for 8 integer bits/component, 3 components, kCGImageAlphaPremultipliedLast.</p> </blockquote> <p>(I don't get an error whenever I provide a SMALLER size as the target size BTW). How can I ROTATE my <code>UIImage</code> 90 degrees CCW using just core graphics functions while preserving the current size?</p> <pre><code>-(UIImage*)reverseImageByScalingToSize:(CGSize)targetSize:(UIImage*)anImage { UIImage* sourceImage = anImage; CGFloat targetWidth = targetSize.height; CGFloat targetHeight = targetSize.width; CGImageRef imageRef = [sourceImage CGImage]; CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef); CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef); if (bitmapInfo == kCGImageAlphaNone) { bitmapInfo = kCGImageAlphaNoneSkipLast; } CGContextRef bitmap; if (sourceImage.imageOrientation == UIImageOrientationUp || sourceImage.imageOrientation == UIImageOrientationDown) { bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo); } else { bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo); } if (sourceImage.imageOrientation == UIImageOrientationRight) { CGContextRotateCTM (bitmap, radians(90)); CGContextTranslateCTM (bitmap, 0, -targetHeight); } else if (sourceImage.imageOrientation == UIImageOrientationLeft) { CGContextRotateCTM (bitmap, radians(-90)); CGContextTranslateCTM (bitmap, -targetWidth, 0); } else if (sourceImage.imageOrientation == UIImageOrientationDown) { // NOTHING } else if (sourceImage.imageOrientation == UIImageOrientationUp) { CGContextRotateCTM (bitmap, radians(90)); CGContextTranslateCTM (bitmap, 0, -targetHeight); } CGContextDrawImage(bitmap, CGRectMake(0, 0, targetWidth, targetHeight), imageRef); CGImageRef ref = CGBitmapContextCreateImage(bitmap); UIImage* newImage = [UIImage imageWithCGImage:ref]; CGContextRelease(bitmap); CGImageRelease(ref); return newImage; } </code></pre>
 

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