使用 C#、WPF 和 DWM 保存窗口的屏幕截图

Question

这是this question的后续问题

上述解决方案使用 DWM 显示活动窗口的缩略图。如果我理解正确，它的工作原理是让您指定要查看的应用程序的窗口句柄，然后让您提供窗口句柄和该窗口上的位置，窗口应在该位置绘制目标窗口的内容。

有没有办法将窗口屏幕截图直接渲染到 BitmapImage 或 Image，而不是直接在窗口中的某个位置绘制它？ （基本上只是抓取窗口的屏幕截图——即使它被另一个窗口覆盖——而不使用更新缩略图。）

感谢您的帮助！

Answer 1

Control.DrawToBitmap 并不总是有效，因此我求助于以下提供更一致结果的本机 API 调用：

实用程序类。调用 Utilities.CaptureWindow(Control.Handle) 捕获特定控件：

public static class Utilities
{
    public static Image CaptureScreen()
    {
        return CaptureWindow(User32.GetDesktopWindow());
    }

    public static Image CaptureWindow(IntPtr handle)
    {

        IntPtr hdcSrc = User32.GetWindowDC(handle);

        RECT windowRect = new RECT();
        User32.GetWindowRect(handle, ref windowRect);

        int width = windowRect.right - windowRect.left;
        int height = windowRect.bottom - windowRect.top;

        IntPtr hdcDest = Gdi32.CreateCompatibleDC(hdcSrc);
        IntPtr hBitmap = Gdi32.CreateCompatibleBitmap(hdcSrc, width, height);

        IntPtr hOld = Gdi32.SelectObject(hdcDest, hBitmap);
        Gdi32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, ApiConstants.SRCCOPY);
        Gdi32.SelectObject(hdcDest, hOld);
        Gdi32.DeleteDC(hdcDest);
        User32.ReleaseDC(handle, hdcSrc);

        Image image = Image.FromHbitmap(hBitmap);
        Gdi32.DeleteObject(hBitmap);

        return image;
    }
}

Gdi32 类：

public class Gdi32
{
    [DllImport("gdi32.dll")]
    public static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hObjectSource, int nXSrc, int nYSrc, int dwRop);
    [DllImport("gdi32.dll")]
    public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth, int nHeight);
    [DllImport("gdi32.dll")]
    public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
    [DllImport("gdi32.dll")]
    public static extern bool DeleteDC(IntPtr hDC);
    [DllImport("gdi32.dll")]
    public static extern bool DeleteObject(IntPtr hObject);
    [DllImport("gdi32.dll")]
    public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
}

User32 类：

public static class User32
{
    [DllImport("user32.dll")]
    public static extern IntPtr GetDesktopWindow();
    [DllImport("user32.dll")]
    public static extern IntPtr GetWindowDC(IntPtr hWnd);
    [DllImport("user32.dll")]
    public static extern IntPtr GetWindowRect(IntPtr hWnd, ref RECT rect);
    [DllImport("user32.dll")]
    public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
}

使用的常量：

    public const int SRCCOPY = 13369376;

使用的结构：

[StructLayout(LayoutKind.Sequential)]
public struct RECT
{
    public int left;
    public int top;
    public int right;
    public int bottom;
}

一个友好的控件扩展方法：

public static class ControlExtensions
{
    public static Image DrawToImage(this Control control)
    {
        return Utilities.CaptureWindow(control.Handle);
    }
}

Answer 2

使用Control.DrawToBitmap Method

Image img = myForm.DrawToBitmap();
Image img = myPanel.DrawToBitmap();