+ (UIImage *)fixOrientation:(UIImage *)aImage {
  // No-op if the orientation is already correct
  if (aImage.imageOrientation ==UIImageOrientationUp)
    return aImage;
  // We need to calculate the proper transformation to make the image upright.
  // We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.
  CGAffineTransform transform =CGAffineTransformIdentity;
  switch (aImage.imageOrientation) {
    caseUIImageOrientationDown:
    caseUIImageOrientationDownMirrored:
      transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height);
      transform = CGAffineTransformRotate(transform, M_PI);
      break;
    caseUIImageOrientationLeft:
    caseUIImageOrientationLeftMirrored:
      transform = CGAffineTransformTranslate(transform, aImage.size.width,0);
      transform = CGAffineTransformRotate(transform, M_PI_2);
      break;
    caseUIImageOrientationRight:
    caseUIImageOrientationRightMirrored:
      transform = CGAffineTransformTranslate(transform, 0, aImage.size.height);
      transform = CGAffineTransformRotate(transform, -M_PI_2);
      break;
    default:
      break;
  }
  switch (aImage.imageOrientation) {
    caseUIImageOrientationUpMirrored:
    caseUIImageOrientationDownMirrored:
      transform = CGAffineTransformTranslate(transform, aImage.size.width,0);
      transform = CGAffineTransformScale(transform, -1, 1);
      break;
    caseUIImageOrientationLeftMirrored:
    caseUIImageOrientationRightMirrored:
      transform = CGAffineTransformTranslate(transform, aImage.size.height,0);
      transform = CGAffineTransformScale(transform, -1, 1);
      break;
    default:
      break;
  }
  // Now we draw the underlying CGImage into a new context, applying the transform
  // calculated above.
  CGContextRef ctx =CGBitmapContextCreate(NULL, aImage.size.width, aImage.size.height,
                       CGImageGetBitsPerComponent(aImage.CGImage),0,
                       CGImageGetColorSpace(aImage.CGImage),
                       CGImageGetBitmapInfo(aImage.CGImage));
  CGContextConcatCTM(ctx, transform);
  switch (aImage.imageOrientation) {
    caseUIImageOrientationLeft:
    caseUIImageOrientationLeftMirrored:
    caseUIImageOrientationRight:
    caseUIImageOrientationRightMirrored:
      // Grr...
      CGContextDrawImage(ctx,CGRectMake(0,0,aImage.size.height,aImage.size.width), aImage.CGImage);
      break;
    default:
      CGContextDrawImage(ctx,CGRectMake(0,0,aImage.size.width,aImage.size.height), aImage.CGImage);
      break;
  }
  // And now we just create a new UIImage from the drawing context
  CGImageRef cgimg =CGBitmapContextCreateImage(ctx);
  UIImage *img = [UIImageimageWithCGImage:cgimg];
  CGContextRelease(ctx);
  CGImageRelease(cgimg);
  return img;
}