将SurfaceImageSource转换为PNG

using System;
using System.IO;
using Windows.Graphics.Capture;
using Windows.Graphics.DirectX;
using Windows.Graphics.Imaging;
using Windows.Storage;
using Windows.UI.Xaml.Media.Imaging;

// 创建SurfaceImageSource对象
SurfaceImageSource surfaceImageSource = new SurfaceImageSource(width, height, isOpaque);

// 创建RenderTarget2D对象
RenderTargetBitmap renderTarget = new RenderTargetBitmap();
await renderTarget.RenderAsync(surfaceImageSource);

// 创建PNG编码器
BitmapEncoder encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, await file.OpenAsync(FileAccessMode.ReadWrite));

// 将RenderTarget2D对象的像素数据复制到一个字节数组中
IBuffer pixelBuffer = await renderTarget.GetPixelsAsync();
byte[] pixels = pixelBuffer.ToArray();

// 设置PNG编码器的像素数据
encoder.SetPixelData(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Premultiplied, (uint)width, (uint)height, 96, 96, pixels);

// 编码并保存为PNG文件
await encoder.FlushAsync();