如何获得控制截图？ DrawToBitmap 不工作

Question

我有一个通过 dll 调用在外部绘制的图片框。

private void myPictureBox_Paint(object sender, PaintEventArgs e)
{
     dllClass.RefreshEx(LWHANDLE, 0, 0);
}

这一切正常，但我现在需要获取该图片框的屏幕截图，但它无法正常工作。

这是我尝试过的：

        Control ctrlToDraw = myPictureBox;

        System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(ctrlToDraw.Width, ctrlToDraw.Height);
        ctrlToDraw.DrawToBitmap(bmp, ctrlToDraw.ClientRectangle); 

我也尝试过通过 Windows API 来实现，但它得到的结果与上面的代码完全相同：一个空白（非空）图像。

除了截取整个屏幕的屏幕截图之外，有人能提出一些建议吗？

Answer 1

我不知道您对外部程序有多少控制权，也不知道它如何绘制到您的图片框，但如果您使用 createGraphics，它将无法工作。

private void button1_Click(object sender, EventArgs e)
    {
        //here I am calling the graphics object of the Picture Box, this will draw to the picture box
        //But the DrawToBitmap, will not reflect this change, and once the Picturebox needs to be updated, this will disappear.
        Graphics g = pictureBox1.CreateGraphics();
        g.DrawRectangle(Pens.Blue, 10, 10, 20, 20);

        System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(pictureBox1.Width, pictureBox1.Height);
        Rectangle bounds = new Rectangle(Left, Top, Width, Height);
        pictureBox1.DrawToBitmap(bmp, pictureBox1.ClientRectangle);
        //Draws whatever is in the PictureBox to the Forms BackgroundImage
        this.BackgroundImage = bmp;
        //It will not draw the Blue rectangle

    }

如果您的外部程序要绘制位图，那么您可以将该位图设置为图片框背景

    Bitmap buffer;
    public Form1()
    {
        InitializeComponent();
        buffer = new Bitmap(pictureBox1.Width, pictureBox1.Height);
    }


    private void button1_Click(object sender, EventArgs e)
    {
        //draw to the bitmap named buffer
        using (Graphics g = Graphics.FromImage(buffer))
        {
            g.DrawRectangle(Pens.Blue, 10, 10, 20, 20);
        }
        //assign the picturebox image to buffer
        pictureBox1.Image = buffer;

        //Now this will show the blue rectangle
        System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(pictureBox1.Width, pictureBox1.Height);
        Rectangle bounds = new Rectangle(Left, Top, Width, Height);
        pictureBox1.DrawToBitmap(bmp, pictureBox1.ClientRectangle);

        this.BackgroundImage = bmp;
    }

编辑魅力第三次

这将截取屏幕截图，剪掉图片框，然后我更改了表单背景，只是为了证明它有效。

你需要添加

using System.Drawing.Imaging;

适用于像素格式。

 private void button1_Click(object sender, EventArgs e)
    {
        using (Graphics G = pictureBox1.CreateGraphics())
        {
            G.DrawRectangle(Pens.Blue, 10, 10, 10, 10);
        }
        Bitmap BMP = new Bitmap(Screen.PrimaryScreen.Bounds.Width,
                                        Screen.PrimaryScreen.Bounds.Height,
                                        PixelFormat.Format32bppArgb);
        using (Graphics GFX = Graphics.FromImage(BMP))
        {
            GFX.CopyFromScreen(Screen.PrimaryScreen.Bounds.X,
                                Screen.PrimaryScreen.Bounds.Y,
                                0, 0,
                                Screen.PrimaryScreen.Bounds.Size,
                                CopyPixelOperation.SourceCopy);
        }
        Bitmap YourPictureBoxImage = new Bitmap(pictureBox1.Width,pictureBox1.Height);
        using (Graphics g = Graphics.FromImage(YourPictureBoxImage))
        {
            Point np = pictureBox1.PointToScreen(new Point(0, 0));
            g.DrawImage(BMP,new Rectangle(0,0,100,100),new Rectangle(np,pictureBox1.Size),GraphicsUnit.Pixel);
        }

        this.BackgroundImage = YourPictureBoxImage;
    }

Answer 2

您可以使用 ALT+PRINTSCREEN 仅截取活动窗口的屏幕截图。这会将当前活动窗口作为位图捕获到剪贴板。将其粘贴到位图编辑工具中，裁剪到您想要的区域。

或者使用允许在屏幕上裁剪目标区域的屏幕捕获实用程序，例如 Evernote 版本 2 的旧屏幕剪辑器。