如何在UWP中为图片添加文本水印？

// 获取Image控件和TextBlock控件
Image imageControl = FindName("imageControl") as Image;
TextBlock watermarkTextBlock = FindName("watermarkTextBlock") as TextBlock;

// 创建RenderTargetBitmap对象并渲染Image控件
RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();
await renderTargetBitmap.RenderAsync(imageControl);

// 创建WriteableBitmap对象并复制像素数据
WriteableBitmap writeableBitmap = new WriteableBitmap(renderTargetBitmap.PixelWidth, renderTargetBitmap.PixelHeight);
await writeableBitmap.SetSourceAsync(await renderTargetBitmap.GetPixelsAsync());

// 在WriteableBitmap上绘制水印文本
using (var stream = writeableBitmap.PixelBuffer.AsStream())
{
    var textRenderer = new CanvasTextRenderer();
    textRenderer.DrawText(stream, writeableBitmap.PixelWidth, writeableBitmap.PixelHeight, watermarkTextBlock.Text, new Point(10, 10), Colors.White, "Arial", 20);
}

// 将带有水印的WriteableBitmap赋值给Image控件的Source属性
imageControl.Source = writeableBitmap;