在 Windows 运行时将文件缩略图另存为图像 [英] Save File Thumbnail as image in windows runtime

问题描述

我想获取存储在 Videos 文件夹中的文件的缩略图，并将它们作为图像保存在我的本地文件夹中.这是我获取文件的代码.

I want to get Thumbnail of files stored in Videos folder and save them as image in my local folder . here is my code to get files .

var v = await KnownFolders.VideosLibrary.GetFilesAsync();
foreach (var file in v)
{
    var thumb = await file.GetScaledImageAsThumbnailAsync(Windows.Storage.FileProperties.ThumbnailMode.SingleItem);
    BitmapImage Img = new BitmapImage();
    Img.SetSource(thumb);
    await ApplicationData.Current.LocalFolder.CreateFolderAsync("VideoThumb");
    var imageFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(
              "VideoThumb\\" + file.Name, CreationCollisionOption.FailIfExists);
    var fs = await imageFile.OpenAsync(FileAccessMode.ReadWrite);
    //I don't know how to save thumbnail on this file !
}

我的项目是一个 Windows Phone 8.1 运行时 C# 应用程序.

my project is a Windows Phone 8.1 Runtime C# app .

推荐答案

您需要处理两件事情:

• 你不需要BitmapImage，因为缩略图提供了一个你可以直接写入文件的流，
• 您没有处理创建文件方法失败(文件存在)的情况，
• create folder 方法将抛出异常，因为文件夹是用 foreach 中的第一个文件创建的(或已经存在).而不是在 foreach 之外创建/打开文件夹，
• 还使用 file.Name 创建图像不是一个好主意，因此这些是视频，它们的扩展名可能是 mp4/mpg/other 而不是 jpg/png/其他,
• 记得在 packageappx.manifest 文件中添加 capabilities.

• you don't need BitmapImage, as thumbnail provides a stream which you can write directly to file,
• you are not handling the case when create file method fails (file exists),
• create folder method will throw exception as the folder is created (or already exists) with the first file in foreach. Rather than that, create/open folder outside foreach,
• also creating image with file.Name is not a good idea, hence those are videos and their extension will likely be mp4/mpg/other not jpg/png/other,
• remember to add capabilities in packageappx.manifest file.

我认为下面的代码应该可以完成这项工作:

I think the below code should do the job:

private async Task SaveViedoThumbnails()
{
    IBuffer buf;
    StorageFolder videoFolder = await ApplicationData.Current.LocalFolder.CreateFolderAsync("VideoThumb", CreationCollisionOption.OpenIfExists);
    Windows.Storage.Streams.Buffer inputBuffer = new Windows.Storage.Streams.Buffer(1024);

    var v = await KnownFolders.VideosLibrary.GetFilesAsync();
    foreach (var file in v)
    {
        var thumb = await file.GetScaledImageAsThumbnailAsync(Windows.Storage.FileProperties.ThumbnailMode.SingleItem);
        var imageFile = await videoFolder.CreateFileAsync(file.DisplayName + ".jpg", CreationCollisionOption.ReplaceExisting);
        using (var destFileStream = await imageFile.OpenAsync(FileAccessMode.ReadWrite))
            while ((buf = (await thumb.ReadAsync(inputBuffer, inputBuffer.Capacity, Windows.Storage.Streams.InputStreamOptions.None))).Length > 0)
                await destFileStream.WriteAsync(buf);
    }
}

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