要捕获最小化窗口的屏幕截图

Question

i am working with MDI application. before minimize any sdi form i want to capture it's screen shot without title bar.my code is working but the way i am capturing image that is not clear rather bit obscure. this way i do it. here is my code.

protected override void WndProc(ref Message m)
        {

            if (m.Msg == WM_COMMAND && m.WParam.ToInt32() == SC_MINIMIZE)
            {
                OnMinimize(EventArgs.Empty);
            }

            base.WndProc(ref m);
        }

protected virtual void OnMinimize(EventArgs e)
        {

            if (_lastSnapshot == null)
            {
                _lastSnapshot = new Bitmap(100, 100);
            }

            using (Image windowImage = new Bitmap(ClientRectangle.Width, ClientRectangle.Height))
            using (Graphics windowGraphics = Graphics.FromImage(windowImage))
            using (Graphics tipGraphics = Graphics.FromImage(_lastSnapshot))
            {
                Rectangle r = this.RectangleToScreen(ClientRectangle);
                windowGraphics.CopyFromScreen(new Point(r.Left, r.Top), Point.Empty, new Size(r.Width, r.Height));
                windowGraphics.Flush();

                float scaleX = 1;
                float scaleY = 1;
                if (ClientRectangle.Width > ClientRectangle.Height)
                {
                    scaleY = (float)ClientRectangle.Height / ClientRectangle.Width;
                }
                else if (ClientRectangle.Height > ClientRectangle.Width)
                {
                    scaleX = (float)ClientRectangle.Width / ClientRectangle.Height;
                }
                tipGraphics.DrawImage(windowImage, 0, 0, 100 * scaleX, 100 * scaleY);
            }
        }

so guide me how should i get the snap of the sdi form which will be better clear and prominent. any idea. thanks.

Answer 1

You scale the picture and any scaling - no matter of up or down-scaling - will lead to a lower quality image. Instead of scaling the image I would get the width and height of the window, create a new bitmap with that size and finally draw the image with the same size as well.

protected virtual void OnMinimize(EventArgs e)
{
    Rectangle r = this.RectangleToScreen(ClientRectangle);

    if (_lastSnapshot == null)
    {
        _lastSnapshot = new Bitmap(r.Width, r.Height);
    }

    using (Image windowImage = new Bitmap(r.Width, r.Height))
    using (Graphics windowGraphics = Graphics.FromImage(windowImage))
    using (Graphics tipGraphics = Graphics.FromImage(_lastSnapshot))
    {
        windowGraphics.CopyFromScreen(new Point(r.Left, r.Top), new Point(0, 0), new Size(r.Width, r.Height));
        windowGraphics.Flush();

        tipGraphics.DrawImage(windowImage, 0, 0, r.Width, r.Height);
    }
}

or something close to the above - I have not actually been able to test it.