I’ve been building a small GUI program with wxPython, and it’s mostly a straightforward experience (if you’re accustomed to the way GUIs tend to be built). wxGlade helps a lot with building the visible components of the UI. But I was going nuts trying to figure out why my Windows icons didn’t look right. I went to the trouble of reading a technote (Icons in Win32) to decide which sizes and depths of icon I needed to provide to get a nice looking taskbar icon and alt-tab icon. But my taskbar icon always came out smeared, clearly having been scaled down from a 32×32 image.

I was ready to start reverse-engineering Windows’ algorithm for picking the icon image, when I thankfully decided to look into the wxGlade-generated code first. Here’s what it gave me for setting the icon in my main frame:

_icon = wx.EmptyIcon()
_icon.CopyFromBitmap(wx.Bitmap("myapp.ico", wx.BITMAP_TYPE_ANY))
self.SetIcon(_icon)

This clearly seems to be picking a single image from the icon, then setting it as the icon. That defeats the whole idea of a multi-image icon. No wonder Windows seems to be scaling a large image for the taskbar. The .ico bitmap loader probably just picks the highest quality image it finds.

Digging deeper into the wxWidgets docs, I found wxIconBundle and wxTopLevelWindow.SetIcons, and came up with this instead:

ib = wx.IconBundle()
ib.AddIconFromFile("myapp.ico", wx.BITMAP_TYPE_ANY)
self.SetIcons(ib)

This works like a charm, giving me pixel-perfect icons for the taskbar and the alt-tab image. Bliss! I couldn’t find much discussion of this issue, or use of these methods in existing code, and I don’t know what it does on other platforms, but it works great on Windows.