使用C＃在Windows Store App中裁剪并保存图像（UIElement）

Question

I already can take a print screen from the actual content of my application. I choose az UIElement (eg a grid), and I render it into a bmp file.

But how can I crop this image as i feel? The code is below works, just the cropping missing. I work for windows 8.1.

public async void SaveVisualElementToFile(UIElement element, StorageFile file)
    {
        var renderTargetBitmap = new RenderTargetBitmap();
        await renderTargetBitmap.RenderAsync(element);
        var pixels = await renderTargetBitmap.GetPixelsAsync();

        using (IRandomAccessStream stream = await 
               file.OpenAsync(FileAccessMode.ReadWrite))
        {
            var encoder = await BitmapEncoder.CreateAsync(
                                              BitmapEncoder.JpegEncoderId, stream);
            byte[] bytes = pixels.ToArray();
            encoder.SetPixelData(BitmapPixelFormat.Bgra8,
                                 BitmapAlphaMode.Ignore,
                                 (uint)renderTargetBitmap.PixelWidth, 
                                 (uint)renderTargetBitmap.PixelHeight,
                                 96, 96, bytes);

            await encoder.FlushAsync();
        }
    } 

Answer 1

There are a couple of ways to do this. There's the traditional way as espoused by MSFT themself. You can also use some extensions such as WinRTXamlToolkit and WriteableBitmapEx . The latter two make it quite easy. Check in their source codes on Codeplex for their sample applications, which will have samples for how to use cropping.