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图片旋转90度解决的方法
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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- //get original photo from iOS photos
- //假设该图片大于2M,会自己主动旋转90度;否则不旋转
- UIImage* originalImg=[dict objectForKey:UIImagePickerControllerOriginalImage];
至于是否正确, 还没确定。
先Mark。
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 {
- // 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;
- }
图片旋转90度解决的方法
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