相机图像改变方向

Question

我一直在尝试将相机图像从 iPhone 上传到我的网络服务器，但之后图像如何改变其方向。这种情况仅发生在相机图像上，而不是从我的机器上传到设备的简单图像上。

下面是代码：

    NSData *imgdataRepresentation = UIImageJPEGRepresentation(imgTemp, 0.5);


    ///////**********************************************
    // setting up the URL to post to
    NSString *addPhotoURL = [NSString stringWithFormat:@"%@%@%@",HTTP_HOST,ADD_PHOTO_URL,[userInfo.userDetail objectForKey:@"id"]];

    // setting up the request object now
    NSMutableURLRequest *request = [[[NSMutableURLRequest alloc] init] autorelease];
    [request setURL:[NSURL URLWithString:addPhotoURL]];
    [request setHTTPMethod:@"POST"];

    /*
     add some header info now
     we always need a boundary when we post a file
     also we need to set the content type

     You might want to generate a random boundary.. this is just the same
     as my output from wireshark on a valid html post
     */
    NSString *boundary = [NSString stringWithString:@"---------------------------14737809831466499882746641449"];
    NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];
    [request addValue:contentType forHTTPHeaderField: @"Content-Type"];

    /*
     now lets create the body of the post
     */
    NSMutableData *body = [NSMutableData data];
    [body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[[NSString stringWithString:@"Content-Disposition: form-data; name=\"Album\"; filename=\"ipodfile.jpg\"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[NSData dataWithData:imgdataRepresentation ]];
    [body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
    // setting the body of the post to the reqeust
    [request setHTTPBody:body];

    // now lets make the connection to the web
    NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
    NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];

Answer 1

无论手机如何握持，iPhone 图像始终以相同的方式存储，但在 EXIF 数据中设置了一个标志，指定图像应处于哪个方向。几乎所有本机 OSX 应用程序（例如 iPhoto 和 Preview）都可以读取此 EXIF 方向正确标记并自动旋转图像，但几乎所有 Windows 应用程序和 Web 浏览器都不考虑方向 EXIF 标记。在保存之前，您必须在网络服务器上手动旋转图像。我不知道您使用哪种 Web 服务器技术，但执行此操作的 C# 代码是：

public static void FixOrientation(this Image image)
{
    // 0x0112 is the EXIF byte address for the orientation tag
    if (!image.PropertyIdList.Contains(0x0112))
    {
        return;
    }

    // get the first byte from the orientation tag and convert it to an integer
    var orientationNumber = image.GetPropertyItem(0x0112).Value[0];

    switch (orientationNumber)
    {
        // up is pointing to the right
        case 8:
            image.RotateFlip(RotateFlipType.Rotate270FlipNone);
            break;
        // up is pointing to the bottom (image is upside-down)
        case 3:
            image.RotateFlip(RotateFlipType.Rotate180FlipNone);
            break;
        // up is pointing to the left
        case 6:
            image.RotateFlip(RotateFlipType.Rotate90FlipNone);
            break;
        // up is pointing up (correct orientation)
        case 1:
            break;
    }
}

Answer 2

您可以使用 imageOrientation 方法获取 UIImage 的图像方向。例如，你想保存从相机拍摄的图像，你可以这样做：

UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
if (image) {
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
    [library writeImageToSavedPhotosAlbum:[image CGImage] 
                              orientation:[image imageOrientation]
                          completionBlock:^(NSURL *assetURL, NSError *error){ /* error handling */ }];
    [library autorelease];
}

然后当你想从库中获取 UIImage 时，你可以通过执行以下操作来检索方向：

UIImage *image = [UIImage imageWithCGImage:[[asset defaultRepresentation] fullResolutionImage] scale:1.0 orientation:[asset orientation]];