Question

Short question:

I know how to draw text on a wx.Bitmap, but how can I draw text on a wx.Icon in wxpython so that it does not appear transparent?

Long question:

I have a wxpython based GUI application, that has a taskbar icon, which I set using mytaskbaricon.SetIcon("myicon.ico").

Now I would like to dynamically put some text on the icon, so I tried to use the wx .DrawText method as explained here.This works fine if I test this for bitmaps (which I use in menu items).

However, the taskbar requires an wxIcon instead of a wxBitmap. So I figured I’ll convert the icon to a bitmap, draw the text, and then convert it back to an icon. This works, except that the text is not shown transparent. Why ? And how can I make the text NOT transparent ?

My code is as roughly follows:

import wx
class MyTaskBarIcon(wx.TaskBarIcon):
  ...
  icon = wx.Icon("myicon.ico", wx.BITMAP_TYPE_ICO)
  bmp = wx.Bitmap("myicon.ico", wx.BITMAP_TYPE_ICO)

  memDC = wx.MemoryDC()
  memDC.SetTextForeground(wx.RED)
  memDC.SelectObject(bmp)
  memDC.DrawText("A", 0, 0)

  icon.CopyFromBitmap(bmp)
  self.SetIcon(icon, APP_NAME_WITH_VERSION)
  ...

So, no errors raised and myicon.ico is shown, but the letter A is transparant (instead of red). If I use a .bmp file to start with (myicon.bmp) the text appears in the correct color (but the borders are jagged). I’ve played around with masks, foreground and background colors, but that didn’t help.

(I am using Windows 7, Python 2.6, wxpython 2.8)

Edit: I’ve shortened my explanation, and made the code more self-contained

Answer 1

Short answer: It seems to me that there is a bug in this particular piece of wx code. I am going to report it and see what comes out of it.

Long answer: You can hack your way around. Setup a color, which is not used in the image. Then draw using that color and when done, fix alpha values and color of those pixels to match your expectation:

import wx
from wx import ImageFromStream, BitmapFromImage, EmptyIcon
import cStringIO, zlib

# ================================ ICON ======================================
def getData():
    return zlib.decompress(
'x\xda\x01\x97\x03h\xfc\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00\x00\x00\x10\
\x00\x00\x00\x10\x08\x06\x00\x00\x00\x1f\xf3\xffa\x00\x00\x00\x04sBIT\x08\
\x08\x08\x08|\x08d\x88\x00\x00\x03NIDAT8\x8dm\xd2ML\x9bu\x00\xc7\xf1\xef\xf3\
<\xed\xda><\xa3@\xcb\x8a\x0cp\xac8\x15\x87\x89/ \x11\xd1d&:5&#n\xc9\\\xa2\
\xc6\xc3b\xe2\xd1y0Y2\xa3q^\xcc\xb8\x9a\xb9\xf9rQc\xc6\x0es\xa4\xd1\x91\xe98\
\xc8\x96\xb98H\xc3\x8b\xc0\xc6\x00\x91\xd2\xb2\xa7}\xda\xe7\xa5\xcf\xd3\xf6\
\xf9{0\xa2\x07\xbf\xf7_\xf29\xfc$\x00\xf1>\xb2\xd9\xc7\tI0$\xc0\xd5d\x06\xa5\
\x17q\xf9O\xa5\x0b$$\x85KB\xa2\xec\xcb\xbc\x1e}\x81\xdf\x01$q\x9a`>\xce\xc9`\
\xc7\x91#\xa1\xce\xa3;\xed\xdbg\xb3s\x19c\xe1\x9cz\xbe*A\x0f\x80\x80\xf4A\
\xeb\xb0\xfcPG\xa2;\x10\x8aI\xe5\xd9\x93\x8bB\xe6`l\x88U)\xf3-\xc7\xc3\xbb_{\
;r\xef\xe1Vci\xa4\xb0\xbc:\x17\xb8\xdczQ\xd3B5"A\x1f\x00\xa7"\xe39\x16\xfb\
\xd6_\xb1wu\x1f@\xa9\x15-k\xe6\xd4j\xa2D\xbf\xec\x95\x91\xe5PGX_\x18),.\xcei\
W\xdb\xbf\xd3:\xb7{49\x0e\xeem\x1dkAG+Z\xb4l\xdf\xc6o-\xc3\xea\x9fK\xbf\x84\
\xe5\xa6\xfe&\xa1>\xa8\xad)\xec\x96n}\xc6`E\xa8g7\x95d\xdbD\xf2\x82\xda\xae\
\x06\x08\xd95\x1e\xeej\xa2\xa1^F \xa1\x1b5\xae\xcf\xe5\xa8D\x14\xea\xf4\xf3\
\xdco\x9es\xb7\x9933\xe1Z\xe9U\t\xe0\xd8\xe7\x17?\t4\xecz7\x99\xd0hp\x05\x87\
\xf6u\x927\x0c6-\x87\xf6\xd6\x16\x00\xaa\x02\xbeN\xdd\xc2\xd7\x04\x99\xec:9K\
\xf9\xf8\xd37\x07\x8e\xcb\x00\x99\xca=\xbd\xbe\x00\xbf\xe4\xb1wO\x0c\xbb*\
\x08\x06\x83\x8c\xfd\xf8\x03E\xc3\xa0\xe2\xba\\\x1a\xfb\x99\xee=q\x8c\xac\
\x83#7RtC\x03\x00\x01\x80r\xd9\xea\xa9z2\x86\xeb\x13\x8bEpk\x82:U\xe5\x8f\
\x95\x15\xc6~\x1a\'=5\xc9\xb3\xcf\xef\xa7q\x87Jn\xd3A4\x04)\x97\xad\x1e\x00\
\x19\xc0\xb3-,\xbb\x82\xe3\xf9\xb85\xa8\xf8\x905J\xd4i\x1a\xe9\xa9I^:0\xc4#\
\xbd}\xb8U\xa8x>\x96]\xc1\xb3-\xb6\x04^\xd9N\x17K\x91gv\xc6\x03,el\xeek\x8b\
\x82\x1c\xe6\xd1\xc7\xfby\xa0g/j\xb4\x1e\xd3\x85\xd5\x8cE0"\x91+\xd9xe;\xfd\
\xaf\xc0\xb1\xae\x14\r\x03\xbd\xecr\xf5\xe6\x06\xc1\x10\xd4\x85\x83<5\xf8$\
\xf1\xc6zB\x80\x16\x86_of\xf1\xf0(\x1a\x06\x9ec]\xd9\x12\xb8\xb63\xea:\xe6\
\xa1\xd9\x9a\xd2-\xb7U\xf9bD\xf0\\o\x82\xaeD\x1d\x08X\xc9Z\x8c^\xcbP4\xd6\
\x99\xdf\xb00\xf3k3\x08e\x14@\xfa\xe7\xeb}GO\xbd\xf5Xr\xc7\xf0BAS[\xe3\x1a\
\xb1P\x08\xc5\x97\xa9\xf9\x82\x8aT\xc5\xf0\\\xaa\xd5*\xaa\xb8k\xa7\xefl\xbes\
\xfd\xcc\xb1\xd3[\x02\x80\xe17\x9e\x98\x8fF\xa3jv3_;12\xaf\xccJ*\xb2\x12\x06\
\xc0\xaf\x95iV+\xbc\xf7rR\xc8rcD\xa2kv\xe0\xcc\xdf;\x19 \x95J5\x17\n\x85\xef\
\xc3\xe10f\xa9`\x98\xf9;\x1f\xda\xb9\xe9qk\xe3\x86nm\xdc\xd0\xed\xdc\xf4\xf8\
\xf2\xf2\xfc\x07\x85B\xdel\x8e\xc7%]\xd7/\xa7R\xa9\xe4\x96\xc04M\xc7q\x9c\
\xb5\x89\x89\x89N!\xc4\xd3S\xdf|4\xcd\xfftw\xff\x97_]\xd3\xf5I\xc0\xf2}\xdf\
\x02\xf8\x0b\xc1.\x9e\xd8Y.\x85\x85\x00\x00\x00\x00IEND\xaeB`\x822\x86\xba\
\xb3' )

def getBitmap():
    return BitmapFromImage(getImage())

def getImage():
    stream = cStringIO.StringIO(getData())
    return ImageFromStream(stream)

def getIcon():
    icon = EmptyIcon()
    icon.CopyFromBitmap(getBitmap())
    return icon

# ============================================================================
class MainWindow(wx.Frame):
    def __init__(self, *args, **kwargs):
        wx.Frame.__init__(self, *args, **kwargs)
        self.number = 0
        self.Bind(wx.EVT_CLOSE, self.OnClose)
        self.panel = wx.Panel(self)
        self.button = wx.Button(self.panel, label="Test")
        self.button.Bind(wx.EVT_BUTTON, self.OnButton)
        self.tbicon = wx.TaskBarIcon()
        self.tbicon.SetIcon(getIcon(), "Test")
        self.sizer = wx.BoxSizer()
        self.sizer.Add(self.button)
        self.panel.SetSizerAndFit(self.sizer)
        self.Show()

#   --------------------------------------------------------------------------
    def OnClose(self, e):
        self.tbicon.Destroy()
        self.Destroy()
        wx.Exit()

#   --------------------------------------------------------------------------
    def OnButton(self, e):
        # HERE WE GO!
        self.number += 1

        bitmap = getBitmap()

        # Find unused color
        image = bitmap.ConvertToImage()
        my_solid_color = wx.Color(*image.FindFirstUnusedColour(0, 0, 0)[1:])

        # Use the unused *unique* color to draw
        dc = wx.MemoryDC()
        dc.SetTextForeground(my_solid_color)
        dc.SelectObject(bitmap)
        dc.DrawText(str(self.number), 0, 0)
        dc.SelectObject(wx.NullBitmap)

        # Convert the bitmap to Image again 
        # and fix the alpha of pixels with that color 
        image = bitmap.ConvertToImage()
        for x in range(image.GetWidth()):
            for y in range(image.GetHeight()):
                p = wx.Colour(image.GetRed(x, y),
                              image.GetGreen(x, y),
                              image.GetBlue(x, y))
                if p == my_solid_color:
                    image.SetAlpha(x, y, 255)   # Clear the alpha
                    image.SetRGB(x, y, 0, 0, 0) # Set the color that we want

        # Convert back to Bitmap and save to Icon
        bitmap = image.ConvertToBitmap() 
        icon = wx.IconFromBitmap(bitmap)
        self.tbicon.SetIcon(icon, "Test")

app = wx.App(False)
win = MainWindow(None)
app.MainLoop()

Note: A had to add some icon. You can ignore that part of the code.