如何在没有我的Winform的情况下获取屏幕截图？ [英] How Do I Get Screenshot Without My Winform On It?

问题描述

我有简单的窗体，只有几个按钮，其中一个应该暂时隐藏表格，将截图复制到剪贴板并返回表格。

这是代码：

I have simple windows form with few buttons, one of them should temporarily hide the form, copy the screenshot to the clipboard and return the form back.
Here is the code:

private void ButtonClick(object sender, EventArgs e)
{
    Hide();
    Clipboard.SetImage(ScreenShot());
    Show();
}

private Image ScreenShot()
{
    var screenSize = Screen.PrimaryScreen.Bounds.Size;
    var image = new Bitmap(screenSize.Width, screenSize.Height);
    using (var g = Graphics.FromImage(image))
    {
        g.CopyFromScreen(Point.Empty, Point.Empty, screenSize);
    }
    return image;
}

在某些情况下，当我点击按钮并从剪贴板粘贴图像时，我会看到我的winform。

据我所知，这是因为屏幕截图是在屏幕实际重新绘制之前拍摄的。

有没有办法避免这种影响？

In some cases when i click the button and paste the image from clipboard somewhere i see my winform on it.
As i understand this happens because screenshot is taken before the screen is actually repainted.
Is there any way to avoid this effect?

推荐答案

一个可能的解决方法：

One possible work-around it this:

this.Opacity = 0;
System.Windows.Forms.Clipboard.SetImage(ScreenShot());
this.Opacity = 1;

通过隐藏（）的可见性控制超出了消息队列，所以这不是一个可靠的调用，就顺序而言操作。正如我所发现的，即使是最低的消息传递优先级 SystemIdle 也会为您提供实际保证隐藏窗口从屏幕渲染中过早的事件。

-SA

Visibility control through Hide() goes outside of the message queue, so this is not a reliable call, in terms of order of operation. As I found, even the lowest messaging priority SystemIdle gives you the event which is too early to actually guarantee hide the window from screen rendering.

—SA

由于我无法重现MSPaint.exe和剪贴板的问题，这是我的测试程序，完成，减少到只有一个文件（不包括项目文件）：

As I could not reproduce the problem with MSPaint.exe and the clipboard, here is my test program, complete, reduced to just one file (not counting project file):

/*
    Referenced assemblies:
    1) System;
    2) System.Windows.Forms;
    3) System.Drawing;
    4) Nothing else.
*/
namespace HideAndCopyForm {
    using System;
    using System.Windows.Forms;
    using System.Drawing;

    public class MainForm : Form {

        public MainForm() {
            Button btn = new Button();
            btn.Text = "&Test";
            btn.Parent = this;
            btn.Click += (sender, eventArgs) => {
                this.Opacity = 0;
                System.Windows.Forms.Clipboard.SetImage(ScreenShot());
                this.Opacity = 1;
            }; //btn.Click
        } //MainForm

        Image ScreenShot() {
            var screenSize = Screen.PrimaryScreen.Bounds.Size;
            var image = new Bitmap(screenSize.Width, screenSize.Height);
            using (var g = Graphics.FromImage(image)) {
                g.CopyFromScreen(Point.Empty, Point.Empty, screenSize);
            }
            return image;
        } //ScreenShot

        [STAThread]
        static void Main() {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new MainForm());
        } //Main

    } //class MainForm

} //namespace HideAndCopyForm

说明：从头开始创建项目，确保上面只显示了3个引用的程序集，删除所有文件，添加上面显示的一个源文件。

有趣的观察： [STAThread] 对于剪贴板操作至关重要，它无法正常工作在 [MTAThread] 。



如果应用程序窗口最大化没问题，如果MSPaint.exe窗口没问题在后台。

-SA

Instructions: create project from scratch, makes sure there are only 3 referenced assemblies shown above, remove all files, add exactly one source file shown above.
Interesting observation: [STAThread] is essential for the clipboard operation, it cannot work in [MTAThread].

No problem if the application window is maximized, no problem if MSPaint.exe window is in background.

—SA

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