我怎样才能获得uiimage的原始nsdata？ [英] How can i get original nsdata of uiimage?

问题描述

在我的应用程序中，用户可以从相册或相机中选择一张可以获得uiimage表示的照片。由于专辑可能有来自网络的图片，因此文件类型不仅仅是jpg。然后我需要将它发送到服务器而不转换。在这里我只能使用nsdata。


我知道UIImageJPEGRepresentation和UIImagePNGRepresentation，但我认为这两种方法可能会转换原始图像。也许当质量设置为1 UIImageJPEGRepresentation可以获得原始图片？


有没有什么方法可以获得原始的uiimage nsdata？

In my app, user can select a pic from album or camera where i can get uiimage representation. Since the album may have pic from web, the file type is not only jpg. Then i need to sent it to the server without convertion. Here i can only use nsdata.
I know UIImageJPEGRepresentation and UIImagePNGRepresentation, but i think this two method may convert the original image. Maybe when quality set to 1 UIImageJPEGRepresentation can get original pic?
Is there any method to get the original uiimage nsdata?

推荐答案

你可以使用 ALAssetsLibrary 和 ALAssetRepresentation 来获取原始数据。示例：

You can use the ALAssetsLibrary and ALAssetRepresentation to get the original data. Example:

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    NSURL *imageURL = [info objectForKey:UIImagePickerControllerReferenceURL];
    ALAssetsLibrary* library = [[ALAssetsLibrary alloc] init];
    [library assetForURL:imageURL resultBlock:^(ALAsset *asset) {
        ALAssetRepresentation *repr = [asset defaultRepresentation];
        NSUInteger size = repr.size;
        NSMutableData *data = [NSMutableData dataWithLength:size];
        NSError *error;
        [repr getBytes:data.mutableBytes fromOffset:0 length:size error:&error];
            /* Now data contains the image data, if no error occurred */
    } failureBlock:^(NSError *error) {
        /* handle error */
    }];
}

但有些事情需要考虑：

• assetForURL：异步工作。


• 在设备上，使用 assetForURL：将导致确认对话框，这可能会刺激用户：

• assetForURL: works asynchronously.
• On the device, using assetForURL: will cause a confirmation dialog, which might be irritating the user:

您的应用想要使用您当前的位置。这允许访问
照片和视频中的位置信息。

"Your App" would like to use your current location. This allows access to location information in photos and videos.

• 如果用户拒绝访问， assetForURL：调用失败块。


• 下次使用此方法时， assetForURL：将失败而不再询问用户。只有在系统设置中重置位置警告时，才会再次询问用户。


• If the user denies access, assetForURL: calls the failure block.
• The next time you use this method, assetForURL: will fail without asking the user again. Only if you reset the location warnings in System Settings, the user is asked again.

因此，您应该准备好此方法失败并且使用 UIImageJPEGRepresentation 或 UIImagePNGRepresentation 作为后备。但在这种情况下，您将无法获得原始数据，例如缺少元数据（EXIF等）。

So you should be prepared that this method fails and use UIImageJPEGRepresentation or UIImagePNGRepresentation as a fallback. But in that case you will not get the original data, e.g. the metadata (EXIF etc.) are missing.

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