How to add Transparent to ColorDialog in C#

Question

I want to add Transparent Color to my ColorDialog.

I tried this code :

MyDialog.CustomColors = new int[] { Color.Transparent.ToArgb() };    
MyDialog.ShowDialog();    
string hex = ColorTranslator.ToHtml(MyDialog.Color);    
MessageBox.Show(hex);

But, when I pick my Custom Color (I mean Transparent), the messageBox show me "White" instead of "Transparent". convert to White itself. But I want to pick Transparent. How can I do that?

Answer 1

My guess is that it is showing the colour behind. Please post your control XAML to be sure.

A common workaround to that is to put a chequerboard pattern behind your swatch control, so that as the alpha is decreased, the chequer shows through. Otherwise, how else do you show something that has no visibility?

Answer 2

The CustomColors property accepts colors in an Int32 composed of the BGR (blue, green, red) and you are passing it an ARGB representation of Transparent color. The A in ARGB controls the alpha channel and transparency. I would put a check box on the form for user to specify color transparency . Else you may map your white in the color dialog box to transparent selection.

If (dlgCol.Color.ToArgb() == Color.White.ToArgb() )
 {
        btnColor.BackColor = Color.Transparent;

 }

http://en.wikipedia.org/wiki/RGBA_color_space