Save File Thumbnail as image in windows runtime

Question

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 !
}

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

Answer 1

There are couple of things you need to handle:

• 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.

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);
    }
}