Problem when using MemoryDC

wxPython Users
1

Why does my code print the lines gray instead of black?

Thanks,
Ram

import wx

class MyFrame(wx.Frame):
    def __init__(self,*args,**kwargs):
        wx.Frame.__init__(self,*args,**kwargs)
        self.panel=wx.Panel(self,-1,size=(1000,1000))
        self.Bind(wx.EVT_PAINT, self.on_paint)
        self.Bind(wx.EVT_SIZE, self.on_size)

        self.bitmap=wx.EmptyBitmapRGBA(1000,1000,255,255,255,255)

        dc=wx.MemoryDC()
        dc.SelectObject(self.bitmap)
        dc.SetPen(wx.Pen(wx.NamedColor("black"),10,wx.SOLID))
        dc.DrawCircle(0,0,30)
        dc.DrawLine(40,40,70,70)
        dc.Destroy()

        self.Show()

    def on_size(self,e=None):
        self.Refresh()

    def on_paint(self,e=None):
        dc=wx.PaintDC(self.panel)
        dc.DrawBitmap(self.bitmap,0,0)
        dc.Destroy()

if __name__=="__main__":
    app=wx.PySimpleApp()
    my_frame=MyFrame(parent=None,id=-1)
    app.MainLoop()

2

cool-RR wrote:

Why does my code print the lines gray instead of black?

They are black for me.

I'm using OS-X 10.4, python2.5, wxPython'2.8.9.1'

What system are you on?

-Chris

···

Thanks,
Ram

import wx

class MyFrame(wx.Frame):
    def __init__(self,*args,**kwargs):
        wx.Frame.__init__(self,*args,**kwargs)
        self.panel=wx.Panel(self,-1,size=(1000,1000))
        self.Bind(wx.EVT_PAINT, self.on_paint)
        self.Bind(wx.EVT_SIZE, self.on_size)

        self.bitmap=wx.EmptyBitmapRGBA(1000,1000,255,255,255,255)

        dc=wx.MemoryDC()
        dc.SelectObject(self.bitmap)
        dc.SetPen(wx.Pen(wx.NamedColor("black"),10,wx.SOLID))
        dc.DrawCircle(0,0,30)
        dc.DrawLine(40,40,70,70)
        dc.Destroy()

        self.Show()

    def on_size(self,e=None):
        self.Refresh()

    def on_paint(self,e=None):
        dc=wx.PaintDC(self.panel)
        dc.DrawBitmap(self.bitmap,0,0)
        dc.Destroy()

if __name__=="__main__":
    app=wx.PySimpleApp()
    my_frame=MyFrame(parent=None,id=-1)
    app.MainLoop()

_______________________________________________
wxpython-users mailing list
wxpython-users@lists.wxwidgets.org
http://lists.wxwidgets.org/mailman/listinfo/wxpython-users

--
Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception

Chris.Barker@noaa.gov

3

I'm using OS-X 10.4, python2.5, wxPython'2.8.9.1'

What system are you on?

win xp, python 2.6, wxpython 2.8.9.2

4

cool-RR wrote:

Why does my code print the lines gray instead of black?

Because drawing on a 32-bit context with alpha has undefined results when using a non alpha-aware DC. You have other problems in your code as well: you're using the frame's paint event to draw the panel, and you've overridden the frame's EVT_SIZE so it's not going to autosize the panel to fill the frame. (Although you can get the same effect of calling Refresh in EVT_SIZE simply by using a non-default style, so it isn't really needed.)

import wx

class MyFrame(wx.Frame):
     def __init__(self,*args,**kwargs):
         wx.Frame.__init__(self,*args,**kwargs)
         self.panel=wx.Panel(self, style=wx.FULL_REPAINT_ON_RESIZE)
         self.panel.Bind(wx.EVT_PAINT, self.on_paint)
         self.panel.Bind(wx.EVT_ERASE_BACKGROUND, lambda e: None)

         self.bitmap=wx.EmptyBitmapRGBA(1000,1000,255,255,255,255)

         dc=wx.GCDC(wx.MemoryDC(self.bitmap))
         dc.SetPen(wx.Pen(wx.NamedColor("black"),10,wx.SOLID))
         dc.DrawCircle(0,0,30)
         dc.DrawLine(40,40,70,70)
         del dc

         self.Show()

     def on_paint(self,e=None):
         dc=wx.PaintDC(self.panel)
         dc.DrawBitmap(self.bitmap,0,0)

if __name__=="__main__":
     app=wx.PySimpleApp()
     my_frame=MyFrame(parent=None,id=-1)
     app.MainLoop()

···

--
Robin Dunn
Software Craftsman

5

Thank you!

Ram.