/**
* 修正图片的转向
*
* @param aImage 原图片
*
* @return 修正后图片
*/

• (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) {
  case UIImageOrientationDown:
  case UIImageOrientationDownMirrored:
  transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height);
  transform = CGAffineTransformRotate(transform, M_PI);
  break;

  case UIImageOrientationLeft:
  case UIImageOrientationLeftMirrored:
      transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
      transform = CGAffineTransformRotate(transform, M_PI_2);
      break;
  
  case UIImageOrientationRight:
  case UIImageOrientationRightMirrored:
      transform = CGAffineTransformTranslate(transform, 0, aImage.size.height);
      transform = CGAffineTransformRotate(transform, -M_PI_2);
      break;
  default:
      break;
  

  }

  switch (aImage.imageOrientation) {
  case UIImageOrientationUpMirrored:
  case UIImageOrientationDownMirrored:
  transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
  transform = CGAffineTransformScale(transform, -1, 1);
  break;

  case UIImageOrientationLeftMirrored:
  case UIImageOrientationRightMirrored:
      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) {
  case UIImageOrientationLeft:
  case UIImageOrientationLeftMirrored:
  case UIImageOrientationRight:
  case UIImageOrientationRightMirrored:
  // 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 = [UIImage imageWithCGImage:cgimg];
  CGContextRelease(ctx);
  CGImageRelease(cgimg);
  return img;
  }