iOS 拍照获取照片 翻转90度的问题

有次在工作开发的过程中,拍照获取照片然后上传,照片会翻转90度,比如竖着的照片会变成横向的

查了一些资料,说是

//如果该图片大于2M，会自动旋转90度；否则不旋转

UIImage* originalImg=[dict objectForKey:UIImagePickerControllerOriginalImage];

这个说法暂时没有仔细去验证,不过有了解决办法,判断照片的方向并翻转(如果有必要)

PS:补充一点这方面的信息,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。

 

上代码

+ (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;

}