最近在做一个项目，需要把相机拍照原图转成Mat ,但发现在把UIImage转成Mat类型时候图像严重变形，最后发现原来是图片的imageOrientation属性所导致。
解决办法：
+ (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; }
