假设把通过相机获取到的图片，直接进行操作, 比方裁剪, 缩放, 则会把原图片向又旋转90度。
ps: 查找过程中, 碰到了一种说法:
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UIImage* originalImg=[dict objectForKey:UIImagePickerControllerOriginalImage];
至于是否正确, 还没确定。 先Mark。
以下的解决的方法亲測可行。 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。
假设我们忽略orientation信息。而直接对比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。这是由于我们运行像素处理或者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。在对比片进行处理之前。先将照片旋转到正确的方向，而且返回的imageOrientaion为0。
以下这种方法就是一个UIImage category中的方法。用它能够达到以上目的。
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- (UIImage *)fixOrientation:(UIImage *)aImage {
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if (aImage.imageOrientation == UIImageOrientationUp)
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return aImage;
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CGAffineTransform transform = CGAffineTransformIdentity;
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switch (aImage.imageOrientation) {
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case UIImageOrientationDown:
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case UIImageOrientationDownMirrored:
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transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height);
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transform = CGAffineTransformRotate(transform, M_PI);
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break;
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case UIImageOrientationLeft:
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case UIImageOrientationLeftMirrored:
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transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
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transform = CGAffineTransformRotate(transform, M_PI_2);
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break;
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case UIImageOrientationRight:
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case UIImageOrientationRightMirrored:
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transform = CGAffineTransformTranslate(transform, 0, aImage.size.height);
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transform = CGAffineTransformRotate(transform, -M_PI_2);
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break;
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default:
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break;
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}
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switch (aImage.imageOrientation) {
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case UIImageOrientationUpMirrored:
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case UIImageOrientationDownMirrored:
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transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
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transform = CGAffineTransformScale(transform, -1, 1);
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break;
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case UIImageOrientationLeftMirrored:
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case UIImageOrientationRightMirrored:
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transform = CGAffineTransformTranslate(transform, aImage.size.height, 0);
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transform = CGAffineTransformScale(transform, -1, 1);
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break;
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default:
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break;
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}
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CGContextRef ctx = CGBitmapContextCreate(NULL, aImage.size.width, aImage.size.height,
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CGImageGetBitsPerComponent(aImage.CGImage), 0,
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CGImageGetColorSpace(aImage.CGImage),
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CGImageGetBitmapInfo(aImage.CGImage));
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CGContextConcatCTM(ctx, transform);
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switch (aImage.imageOrientation) {
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case UIImageOrientationLeft:
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case UIImageOrientationLeftMirrored:
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case UIImageOrientationRight:
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case UIImageOrientationRightMirrored:
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CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.height,aImage.size.width), aImage.CGImage);
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break;
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default:
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CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.width,aImage.size.height), aImage.CGImage);
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break;
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}
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CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
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UIImage *img = [UIImage imageWithCGImage:cgimg];
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CGContextRelease(ctx);
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CGImageRelease(cgimg);
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return img;
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}
