http://www.tuicool.com/articles/IfEZre

今天写demo的时候发现, 如果把通过相机获取到的图片，直接进行操作, 比如裁剪, 缩放, 则会把原图片向又旋转90度。

刚开始觉得莫名其妙, 不知所措。 后来百度了一下，找到了解决办法。

ps: 查找过程中, 碰到了一种说法:

//get original photo from iOS photos
//如果该图片大于2M，会自动旋转90度；否则不旋转
UIImage* originalImg=[dict objectForKey:UIImagePickerControllerOriginalImage];

至于是否正确, 还没确定。 先Mark。

下面的解决办法亲测可行。 原文:http://www.cnblogs.com/jiangyazhou/archive/2012/03/22/2412343.html

- (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; }