最近在接入一個拍照翻譯的api時，發(fā)現(xiàn)用自帶相機拍攝的照片傳上去時返回的文字的rect對不上，而去相冊里把照片截屏再上傳之又是正常的，在排查了一段時間之后終于在輸出照片的大小時發(fā)現(xiàn)了端倪

CGFloat imageW = CGImageGetWidth(photo.CGImage);
CGFloat imageH = CGImageGetHeight(photo.CGImage);

在用上面的方法輸出圖片的高度和寬度時，發(fā)現(xiàn)用相機拍攝的照片輸出的寬度居然大于高度，可UIimageView里顯示的照片明顯是高度比寬度大一些的，于是上網(wǎng)搜索有關(guān)資料，果不其然：

相機拍照后直接取出來的UIimage（用UIImagePickerControllerOriginalImage取出），它本身的imageOrientation屬性是3，即UIImageOrientationRight。如果這個圖片直接使用則沒事，但是如果對它進行裁剪、縮放等操作后，它的這個imageOrientation屬性會變成0。此時這張圖片用在別的地方就會發(fā)生旋轉(zhuǎn)。imageOrientation是只讀的，不能直接修改其值。

最坑的地方在于，UIimageView在使用照片的時候會自動旋轉(zhuǎn)回來，這給人的誤導(dǎo)就是如果不通過CGImageGetHeight的方式輸出照片的寬高，根本無法發(fā)現(xiàn)這個問題！因為你看到屏幕上顯示的圖片確實是正常的

知道了原因，解決起來就簡單了，給UIImage寫一個分類解決這個問題：

- (UIImage *)fixOrientation{
    // No-op if the orientation is already correct
    UIImage *image = self;
    if (image.imageOrientation == UIImageOrientationUp)
        return image;
    // 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 (image.imageOrientation) {
        case UIImageOrientationDown:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width, image.size.height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width,0);
            transform = CGAffineTransformRotate(transform, M_PI_2);
            break;
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, 0, image.size.height);
            transform = CGAffineTransformRotate(transform, -M_PI_2);
            break;
        default:
            break;
    }
    switch (image.imageOrientation) {
        case UIImageOrientationUpMirrored:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width,0);
            transform = CGAffineTransformScale(transform, -1, 1);
            break;
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, image.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, image.size.width, image.size.height,
                                            CGImageGetBitsPerComponent(image.CGImage),0,
                                            CGImageGetColorSpace(image.CGImage),
                                            CGImageGetBitmapInfo(image.CGImage));
    CGContextConcatCTM(ctx, transform);
    switch (image.imageOrientation) {
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            // Grr...
            CGContextDrawImage(ctx,CGRectMake(0,0,image.size.height,image.size.width), image.CGImage);
            break;
        default:
            CGContextDrawImage(ctx,CGRectMake(0,0,image.size.width,image.size.height), image.CGImage);
            break;
    }
    // And now we just create a new UIImage from the drawing context
    CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
    UIImage *resultImg = [UIImage imageWithCGImage:cgimg];
    CGContextRelease(ctx);
    CGImageRelease(cgimg);
    return resultImg;
}

使用時，直接調(diào)用- (UIImage *)fixOrientation方法即可