C#实现将桌面截屏为图片

网友Omar Abid问？

我想通过代码获取当前的电脑屏幕并保存为一张图片，就好像键盘的 截屏 按钮功能，请问这该如何实现？我没有好思路。

网友Gary Willoughby回答：

如果你的程序是 framework >2.0 的话，完全可以使用 CopyFromScreen() 方法，参考如下代码：.

//Create a new bitmap.
var bmpScreenshot = new Bitmap(Screen.PrimaryScreen.Bounds.Width,
                               Screen.PrimaryScreen.Bounds.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(Screen.PrimaryScreen.Bounds.X,
                            Screen.PrimaryScreen.Bounds.Y,
                            0,
                            0,
                            Screen.PrimaryScreen.Bounds.Size,
                            CopyPixelOperation.SourceCopy);

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

网友colton7909回答：

要想完美的通过代码截屏，通常有两个坑需要解决。

默认情况下是不能截图到扩展屏的，也就是 多显示器 的情况。
当显示屏设置了扩大或缩小展示，比如 125%，150% ，那么 Screen 返回的数值会是错误的。

解决这两个问题，最好的方式就是通过 p/invoke 调用底层的 win32 api 来实现，参考如下代码：

using System.Drawing;
using System.Linq;
using System.Runtime.InteropServices;
using System.Windows.Forms;
class Program
{
    const int ENUM_CURRENT_SETTINGS = -1;
    static void Main()
    {
        foreach (Screen screen in Screen.AllScreens)
        {
            DEVMODE dm = new DEVMODE();
            dm.dmSize = (short)Marshal.SizeOf(typeof(DEVMODE));
            EnumDisplaySettings(screen.DeviceName, ENUM_CURRENT_SETTINGS, ref dm);

            using (Bitmap bmp = new Bitmap(dm.dmPelsWidth, dm.dmPelsHeight))
            using (Graphics g = Graphics.FromImage(bmp))
            {
                g.CopyFromScreen(dm.dmPositionX, dm.dmPositionY, 0, 0, bmp.Size);
                bmp.Save(screen.DeviceName.Split('\\').Last() + ".png");
            }
        }
    }

    [DllImport("user32.dll")]
    public static extern bool EnumDisplaySettings(string lpszDeviceName, int iModeNum, ref DEVMODE lpDevMode);

    [StructLayout(LayoutKind.Sequential)]
    public struct DEVMODE
    {
        private const int CCHDEVICENAME = 0x20;
        private const int CCHFORMNAME = 0x20;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 0x20)]
        public string dmDeviceName;
        public short dmSpecVersion;
        public short dmDriverVersion;
        public short dmSize;
        public short dmDriverExtra;
        public int dmFields;
        public int dmPositionX;
        public int dmPositionY;
        public ScreenOrientation dmDisplayOrientation;
        public int dmDisplayFixedOutput;
        public short dmColor;
        public short dmDuplex;
        public short dmYResolution;
        public short dmTTOption;
        public short dmCollate;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 0x20)]
        public string dmFormName;
        public short dmLogPixels;
        public int dmBitsPerPel;
        public int dmPelsWidth;
        public int dmPelsHeight;
        public int dmDisplayFlags;
        public int dmDisplayFrequency;
        public int dmICMMethod;
        public int dmICMIntent;
        public int dmMediaType;
        public int dmDitherType;
        public int dmReserved1;
        public int dmReserved2;
        public int dmPanningWidth;
        public int dmPanningHeight;
    }
}

没想到截个屏还有这么多坑需要解决，不过用了 win32 api，那就限定了 windows 平台，不知道大家可有什么好的跨平台解决方案呢？

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