How to get bitmap from painted panel in C#

问题

I have a panel and I use it's Graphics gr = panel1.CreateGraphics() to draw lines and other stuff. I need to get pixel color of the point where mouse is clicked, so I decided to use GetPixel method of Bitmap. I create bitmap this way:

Bitmap b = new Bitmap(width, height);            
panel1.DrawToBitmap(b, new Rectangle(0, 0, width, height));
b.Save("D:/aaa.bmp");

but I get only white rectangle even if I've drawn anything. What's the problem?

回答1:

Only things that are drawn in the Paint event will be rendered by DrawToBitmap. Instead of explicitly call panel1.CreateGraphics(), handle the Paint event of the panel and do your drawing using e.Graphics.

来源：https://stackoverflow.com/questions/8553794/how-to-get-bitmap-from-painted-panel-in-c-sharp