Hello,
I would like to use wxPython to create simple images consisting of graphical
primitives, save them as *.PNG files, and visualize them inside a wx.Frame
on a wx.Panel. I have written a small sample program to demonstrate with a
simple example how that could be achieved. Even eith this simple program,
there are two things that I don't understand.
1. The space that is reserved on the wx.Panel to display the contents of the
wx.DC is the size of bitmap that sits "behind" the wx.MemoryDC. In lines 33
and 34, I try to change the size of the bitmap, but that seems to be ignored
when the wx.Panel is finally drawn. All that I see is the area that
corresponds to the bitmaps original size. How can I adjust the size of the
bitmap or the device context after creation?
2. When I try to change the size of the bitmap, I get an empty *.PNG file
without drawing. When I comment out these two lines, I get the expected
content in the created PNG. The contents of the wx.Panel are the same in
both cases. What is the reason for the different ouput in the file?
Here is my sample program:
import wx
···
#______________________________________________
class BitmapPanel(wx.Panel):
def __init__(self,id,parent,virtualDC):
wx.Panel.__init__(self,parent,id)
self.virtualDC = virtualDC
self.Bind(wx.EVT_PAINT,self.OnPaint)
def OnPaint(self,event):
dc = wx.PaintDC(self)
dc.Blit(0,0,1024,768,self.virtualDC,0,0)
#______________________________________________
class VirtualBitmap(wx.MemoryDC):
def __init__(self,width=200,height=200):
wx.MemoryDC.__init__(self)
self.width = width
self.height = height
self.bitmap = wx.EmptyBitmap(width,height)
self.SelectObject(self.bitmap)
self.Clear()
def SaveFile(self,name,bmptype=wx.BITMAP_TYPE_PNG):
return self.bitmap.SaveFile(name,bmptype)
#______________________________________________
def DrawGrid(panel):
border = 5
size = 24
lineNumber = 30
panel.bitmap.SetWidth(lineNumber*size+border*2)
panel.bitmap.SetHeight(lineNumber*size+border*2)
for i in range(lineNumber):
#draw vertical lines
panel.DrawLine(border+i*size,border,border+i*size,border+(lineNumber-1)*size)
#draw horizontal lines
panel.DrawLine(border,border+i*size,border+(lineNumber-1)*size,border+i*size)
if __name__ == '__main__':
app = wx.PySimpleApp()
width = 500
height = 500
img = VirtualBitmap(width,height)
brush = wx.Brush(wx.Colour(120,120,120),wx.SOLID)
pen = wx.Pen(wx.Colour(120,120,120),3,wx.SOLID)
img.SetBrush(brush)
img.SetPen(pen)
pen.SetCap(wx.CAP_BUTT)
DrawGrid(img)
bool = img.SaveFile("wxBitmap.png",wx.BITMAP_TYPE_PNG)
if not bool:
print "Couldn't save"
frame = wx.Frame(None,-1,"View")
panel = BitmapPanel(-1,frame,img)
panel.SetSize((1024,768))
frame.Fit()
frame.Show(True)
app.MainLoop()
I work with Python 2.3.4, wxPython 2.6.0.1 on WindowsME.
Many thanks for your explanations and hints
Piet
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Thanks Chris!