ios - 从 Assets Library URL iOS 获取 MIME 类型

Question

我正在尝试上传图片，但在发布请求中我需要传递“Content-Type”，即我从 iOS 照片库中选择的图片的 mime 类型，但是当我试图获取mime 类型它即将到来 nil。

这是过程:-

注意: imgProfileURL 的类型是NSString

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
    {
        imgProfileURL=[NSString stringWithFormat:@"%@",[info objectForKey:@"UIImagePickerControllerReferenceURL"]];

    }

imgProfileURL 现在包含:-

assets-library://asset/asset.JPG?id=B6C0A21C-07C3-493D-8B44-3BA4C9981C25&ext=JPG

现在，我调用下面的函数来获取 MIME 类型并传递 imgProfileURL 的值

- (NSString *)mimeTypeForPath:(NSString *)path
{
    // get a mime type for an extension using MobileCoreServices.framework



    CFStringRef extension = (__bridge CFStringRef)[path pathExtension];
    CFStringRef UTI = UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension, extension, NULL);
    assert(UTI != NULL);

    NSString *mimetype = CFBridgingRelease(UTTypeCopyPreferredTagWithClass(UTI, kUTTagClassMIMEType));  //it is NULL
    assert(mimetype != NULL); // Crashing here

    CFRelease(UTI);

    return mimetype;
}

mimetype 在这里变为 NULL。

我已经回答了这个问题，但没有帮助我:- LINK

Answer 1

这是我获取图像名称、类型和大小所做的:

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    UIImage *imgSelected = [info objectForKey:@"UIImagePickerControllerOriginalImage"];
    NSURL *fileURL = [info valueForKey:UIImagePickerControllerReferenceURL];

    ALAssetsLibraryAssetForURLResultBlock resultblock = ^(ALAsset *myasset)
    {
        ALAssetRepresentation *representation = [myasset defaultRepresentation];
        NSString *fileName = [representation filename];
        NSString *fileSize = [NSString stringWithFormat:@"%lld",[representation size]];
        NSString *MIMEType = (__bridge_transfer NSString*)UTTypeCopyPreferredTagWithClass
        ((__bridge CFStringRef)[representation UTI], kUTTagClassMIMEType);

        NSLog(@"file name : %@",fileName);
        NSLog(@"file size : %@",fileSize);
        NSLog(@"file type : %@",MIMEType);
    };

    ALAssetsLibrary* assetslibrary = [[ALAssetsLibrary alloc] init] ;
    [assetslibrary assetForURL:fileURL resultBlock:resultblock failureBlock:nil];
}