如何在Metro C#应用程序中捕获屏幕

在Metro C#应用程序中捕获屏幕，可以使用Windows的API函数。以下是一个简单的示例代码，用于捕获整个屏幕并将其保存为PNG格式的图像文件：

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;

public class ScreenCapture
{
    [DllImport("user32.dll")]
    private static extern IntPtr GetDesktopWindow();

    [DllImport("user32.dll")]
    private static extern IntPtr GetWindowDC(IntPtr hWnd);

    [DllImport("gdi32.dll")]
    private static extern IntPtr CreateCompatibleBitmap(IntPtr hdc, int nWidth, int nHeight);

    [DllImport("gdi32.dll")]
    private static extern IntPtr CreateCompatibleDC(IntPtr hdc);

    [DllImport("gdi32.dll")]
    private static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);

    [DllImport("gdi32.dll")]
    private static extern bool BitBlt(IntPtr hdcDest, int xDest, int yDest, int wDest, int hDest, IntPtr hdcSource, int xSrc, int ySrc, CopyPixelOperation rop);

    [DllImport("gdi32.dll")]
    private static extern bool DeleteObject(IntPtr hObject);

    [DllImport("gdi32.dll")]
    private static extern bool DeleteDC(IntPtr hdc);

    [DllImport("user32.dll")]
    private static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);

    public static Bitmap CaptureScreen()
    {
        IntPtr hdc = GetWindowDC(GetDesktopWindow());
        int width = Screen.PrimaryScreen.Bounds.Width;
        int height = Screen.PrimaryScreen.Bounds.Height;
        IntPtr compatibleDeviceContext = CreateCompatibleDC(hdc);
        IntPtr compatibleBitmap = CreateCompatibleBitmap(hdc, width, height);
        IntPtr oldBitmap = SelectObject(compatibleDeviceContext, compatibleBitmap);
        BitBlt(compatibleDeviceContext, 0, 0, width, height, hdc, 0, 0, CopyPixelOperation.SourceCopy | CopyPixelOperation.CaptureBlt);
        Bitmap bitmap = Image.FromHbitmap(compatibleBitmap);
        SelectObject(compatibleDeviceContext, oldBitmap);
        DeleteObject(compatibleBitmap);
        DeleteDC(compatibleDeviceContext);
        ReleaseDC(GetDesktopWindow(), hdc);
        return bitmap;
    }
}

在上面的代码中，我们使用了Windows API函数来捕获屏幕，并将其保存为Bitmap格式的图像。在Metro C#应用程序中，可以使用以下代码来保存Bitmap格式的图像为PNG格式的文件：

private void SaveBitmapAsPng(Bitmap bitmap, string filePath)
{
    ImageCodecInfo imageCodecInfo = GetEncoderInfo("image/png");
    EncoderParameters encoderParameters = new EncoderParameters(1);
    encoderParameters.Param[0] = new EncoderParameter(Encoder.Quality, 100L);
    bitmap.Save(filePath, imageCodecInfo, encoderParameters);
}

private ImageCodecInfo GetEncoderInfo(string mimeType)
{
    ImageCodecInfo[] imageCodecInfos = ImageCodecInfo.GetImageEncoders();
    for (int i = 0; i< imageCodecInfos.Length; i++)
    {
        if (imageCodecInfos[i].MimeType == mimeType)
        {
            return imageCodecInfos[i];
        }
    }
    return null;
}

在上面的代码中，我们使用了ImageCodecInfo类来获取PNG格式的编码器信息，并使用EncoderParameters类来设置编码器的参数。最后，我们使用Bitmap类的Save方法来将Bitmap格式的图像保存为PNG格式的文件。