ICommand-Bitmap: Transparency Trick?

AndryJoos

Hey ESRI-Staff

First of all - the new icons on the toolbars in ArcGIS 9.4 Beta 1 look awesome compared to what was there before. We're currently planning in "upgrading" our own icons, too.

I noticed, that the "old" rule of the color of the upper left pixel being threatened as the transparent color still is in effect - however ESRI seems to have icons where this doesn't apply: For example, all the "Show window" icons (show Pyhton window, search window ...) do have another transparency color set than what's on the upper left pixel (the upper left pixel is part of the "iconized application window"-picture). Can you confirm this?

And how would it be possible to achieve the same result (using the C++ API) - any tricks? Can the toolbars finally treat transparent PNGs?

Greetings,
Andry

AndryJoos

I would be curious to hear how you solved this problem, I am facing something similar with legacy ICommands

Just a few general hints (or do you work with Delphi?)

* I load the PNG image from the resource file using a ressource stream
* Create a new BITMAPV5Header and mask the colors properly (which seems to be the only way to make GDI accept alpha values)
* Use CreateDIBSection using the new header
* Then a bitwise (or scanline-wise) copy of the pixel data from the previously loaded PNG ressource to the DIB
* This results in a bitmap handle that works for ESRI's toolbars...

.. full alpha transparency looks just better 😉 The thing I like about this solution is that it really does the job for 100% working alpha transparency and no nasty premultiplied alpha tricks are needed (which wouldn't properly work with the gradient background of the toolbars anyway).

Best regards,
Andry