Image decompression

gistfile1.txt

+ (UIImage *)decompressedImageWithImage:(UIImage *)image resizeTo:(CGSize)targetSize
{
  CGImageRef imageRef = image.CGImage;
  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
  CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef);
  BOOL sameSize = NO;
  if (CGSizeEqualToSize(targetSize, CGSizeMake(CGImageGetWidth(imageRef), CGImageGetHeight(imageRef)))) {
    targetSize = CGSizeMake(1, 1);
    sameSize = YES;
  }
  size_t imageWidth = (size_t)targetSize.width;
  size_t imageHeight = (size_t)targetSize.height;
  CGContextRef context = CGBitmapContextCreate(NULL,
      imageWidth,
      imageHeight,
      8,
      // Just always return width * 4 will be enough
      imageWidth * 4,
      // System only supports RGB, set explicitly
      colorSpace,
      // Makes system don't need to do extra conversion when displayed.
      alphaInfo | kCGBitmapByteOrder32Little);
  CGColorSpaceRelease(colorSpace);
  if (!context) {
    return nil;
  }


  CGRect rect = (CGRect){CGPointZero, {imageWidth, imageHeight}};
  CGContextDrawImage(context, rect, imageRef);
  if (sameSize) {
    CGContextRelease(context);
    return image;
  }
  CGImageRef decompressedImageRef = CGBitmapContextCreateImage(context);
  CGContextRelease(context);

  UIImage *decompressedImage = [[UIImage alloc] initWithCGImage:decompressedImageRef scale:image.scale orientation:image.imageOrientation];
  CGImageRelease(decompressedImageRef);
  return decompressedImage;
}