Is there a way to achieve real transparency with ToolboxBitmap?

Question

I'm creating icons for my usercontrols using Paint.NET. I'd like to have proper transparency like 32 bit PNG or BMPX provides. Is there a way to achieve that? Looking at the toolbox, the regular Label control does seem to use a fully transparent icon (unless MS assumes an always white toolbox background?).

Currently I'm embedding my icons as bitmaps compiled to embedded resource, and use the ToolboxBitmapAttribute(Type, String) constructor. I tried using ICO or PNG or BMPX, but none of those work at all, they don't even get displayed, whereas a simple BMP does get displayed (using the lower left corner pixel color as transparent color).

*Real* transparency? No. But faked transparency works just fine, if you use a bitmap. Hans explains all the details below. — Cody Gray - on strike, Jun 15 '11 at 13:27
Thanks. Pity though, I've come to appreciate the AntiAliasing capabilities of PDN over the last months. — takrl, Jun 15 '11 at 13:49

Hans Passant · Accepted Answer · 2011-06-15T13:23:03.533

3

The built-in Winforms toolbox bitmaps use Color.Fuchsia as the background color. A pretty standard choice as the Bitmap.MakeTransparent() color, it is a nice fuchsed up color that is unlikely to cause unintended transparency in the rest of the image. Here's the one for the Label control, retrieved from the System.Windows.Forms.dll assembly:

enter image description here

It got turned into a PNG while uploading it, it is actually a BMP.

edited Jun 15 '11 at 13:23

answered Jun 15 '11 at 13:17

Hans Passant

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Thanks. I had no idea how to extract the original image from System.Windows.Forms, otherwise I'd probably have checked that first. I remember that color from the VB6 days, it was used for the same purpose back then as well. – takrl Jun 15 '11 at 13:50

Is there a way to achieve real transparency with ToolboxBitmap?

1 Answers1