iOS开发- 相机(摄像头)获取到的图片自动旋转90度解决办法

  今天要做一个读取摄像头图片功能，发现拍摄之后的图片会在拍摄水平的基础上自动发生90°旋转。通过下面的方法 确实修正了，未避免选照片也发生该案例，我觉得在选取图片的时候也要进行修正。Mark!感谢 原文 http://blog.youkuaiyun.com/hitwhylz/article/details/39518463

 //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

  网络上说：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。

修正代码如下：

- (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;
}