如何从窗口获取屏幕截图？

Question

I'm having trouble by taking a screenshot of a window.

This is the code I'm using:

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

namespace Alerts
{
    class ImgSearch
    {
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern IntPtr FindWindow(string strClassName, string strWindowName);
        [DllImport("user32.dll")]
        public static extern bool GetWindowRect(IntPtr hwnd, ref Rect rectangle);

        public struct Rect
        {
            public int Left { get; set; }
            public int Top { get; set; }
            public int Right { get; set; }
            public int Bottom { get; set; }
        }

        public static void ScreenShotWindow(IntPtr whandle)
        {
            // Get the window rectangle
            Rect window = new Rect();
            GetWindowRect(whandle, ref window);

            // Get window size
            int width = window.Right - window.Left;
            int height = window.Bottom - window.Top;
            Size size = new Size();
            size.Width = width;
            size.Height = height;

            //Create a new bitmap.
            var bmpScreenshot = new Bitmap(width,
                                           height,
                                           PixelFormat.Format32bppArgb);

            // Create a graphics object from the bitmap.
            var gfxScreenshot = Graphics.FromImage(bmpScreenshot);                

            // Take the screenshot from the upper left corner to the right bottom corner.
            gfxScreenshot.CopyFromScreen(window.Left,
                                        window.Right,
                                        0,
                                        0,
                                        size,
                                        CopyPixelOperation.SourceCopy);

            // Save the screenshot to the specified path that the user has chosen.
            bmpScreenshot.Save("Screenshot.png", ImageFormat.Png);
        }
    }
}

This is the result:

So as you can see the image is empty, and I expected to get an image like this:

I'm 100% sure the window handle is not the problem because GetWindowRect is working perfectly

Answer 1

There is a small mistake in the code that can be easily overlooked.

gfxScreenshot.CopyFromScreen(window.Left,
  window.Top, // window.Top instead of window.Right
  0,
  0,
  size,
  CopyPixelOperation.SourceCopy);

Instead of window.Right you should use window.Top here. The second parameter is the Y coordinate of the area.