相机(摄像头)获取到的图片自动旋转90度解决办法

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

用相机拍摄出来的照片含有EXIF信息，UIImage的imageOrientation属性指的就是EXIF中的orientation信息。

如果我们忽略orientation信息，而直接对照片进行像素处理或者drawInRect等操作，得到的结果是翻转或者旋转90之后的样子。这是因为我们执行像素处理或者drawInRect等操作之后，imageOrientaion信息被删除了，imageOrientaion被重设为0，造成照片内容和imageOrientaion不匹配。

所以，在对照片进行处理之前，先将照片旋转到正确的方向，并且返回的imageOrientaion为0。

下面这个方法就是一个UIImage category中的方法，用它可以达到以上目的。

- (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;}