demo/ImageAlpha.py

#!/usr/bin/env python

import wx
from Main import opj


#----------------------------------------------------------------------

msg = "Some text will appear mixed in the image's shadow..."

class TestPanel(wx.Panel):
    def __init__(self, parent, log):
        self.log = log
        wx.Panel.__init__(self, parent, -1)

        self.Bind(wx.EVT_PAINT, self.OnPaint)


    def OnPaint(self, evt):
        dc = wx.PaintDC(self)
        dc.SetBackground(wx.Brush("WHITE"))
        dc.Clear()

        dc.SetFont(wx.Font(16, wx.FONTFAMILY_SWISS, wx.FONTSTYLE_NORMAL, wx.FONTWEIGHT_BOLD, True))
        dc.DrawText("Bitmap alpha blending (on all ports but gtk+ 1.2)",
                    25,25)

        bmp = wx.Bitmap(opj('bitmaps/toucan.png'))
        if "gtk1" in wx.PlatformInfo:
            # Try to make up for lack of alpha support in wxGTK (gtk+
            # 1.2) by converting the alpha blending into a
            # transparency mask.

            # first convert to a wx.Image
            img = bmp.ConvertToImage()

            # Then convert the alpha channel to a mask, specifying the
            # threshold below which alpha will be made fully
            # transparent
            img.ConvertAlphaToMask(220)

            # convert back to a wx.Bitmap
            bmp = img.ConvertToBitmap()


        dc.DrawBitmap(bmp, 25,100, True)

        dc.SetFont(self.GetFont())
        y = 75
        for line in range(10):
            y += dc.GetCharHeight() + 5
            dc.DrawText(msg, 200, y)
        dc.DrawBitmap(bmp, 250,100, True)


#----------------------------------------------------------------------

def runTest(frame, nb, log):
    win = TestPanel(nb, log)
    return win

#----------------------------------------------------------------------


overview = """<html><body>
<h2><center>Images with Alpha</center></h2>

wxMSW and wxMac now support alpha channels of supported image
types, and will properly blend that channel when drawing a
bitmap.  It is not supported yet on wxGTK, (if you would like to
change that please submit a patch!)

<p>On wxGTK this demo turns the alpha channel into a 1-bit mask, so
yes, it looks like crap.  Please help us fix it!

</body></html>
"""


if __name__ == '__main__':
    import sys,os
    import run
    run.main(['', os.path.basename(sys.argv[0])] + sys.argv[1:])