wxPython - API di disegno

GDI+ (Interfaccia di disegno grafico), CoreGraphics e Cairo librariesformano il framework dell'API di disegno in wxPython. wx.GraphicsContext è l'oggetto drawable principale, utilizzando il quale vengono creati vari oggetti Device Context.

wx.DC è una classe astratta. Le sue classi derivate vengono utilizzate per eseguire il rendering di grafica e testo su dispositivi diversi. Le classi Device Context sono:

  • wx.ScreenDC - Usa questo per dipingere sullo schermo, al contrario di una singola finestra.

  • wx.ClientDC - Usalo per dipingere nell'area client della finestra (la parte senza bordi e altre decorazioni), ma non usarlo dall'interno di un wxPaintEvent.

  • wx.PaintDC − Use this to paint on the client area of the window, but only from within a wxPaintEvent.

  • wx.WindowDC − Use this to paint on the whole area of the window, including decorations. This may not be available on non-Windows platforms.

Drawing API of wxPython offers different functions for drawing shape, text and image. Objects required for drawing purpose, like Colour, Pen, Brush and Font can also be constructed using GDI classes.

wx.Colour Class

Colour object represents combination of RGB (RED, Green and Blue) intensity values, each on the scale of 0-255. There are a few predefined colour objects like −

  • wxBLACK
  • wxBLUE
  • wxCYAN
  • wxGREEN
  • wxYELLOW
  • wxLIGHT_GREY
  • wxRED
  • wxWHITE

Color with custom combination of RGB values is formed as wx.Colour object.

wx.Colour(r,g,b)

wx.Pen Class

Pen object determines the colour, width and style of the shape of graphics like line, rectangle, circle etc.

Predefined Pen objects are −

wxBLACK_DASHED_PEN
wxBLACK_PEN
wxBLUE_PEN
wxCYAN_PEN
wxGREEN_PEN
wxYELLOW_PEN
wxGREY_PEN
wxLIGHT_GREY_PEN
wxMEDIUM_GREY_PEN
wxRED_PEN
wxTRANSPARENT_PEN
wxWHITE_PEN

Predefined Pen styles are −

wx.SOLID
wx.DOT
wx.LONG_DASH
wx.SHORT_DASH
wx.DOT_DASH
wx.TRANSPARENT

wx.Brush Class

Brush is another elementary graphics object required to fill the backgrounds of shapes such as rectangle, ellipse, circle etc.

A custom Brush object requires wx.Colour and Brush style parameters. The following is a list of predefined brush styles −

wx.SOLID
wx.STIPPLE
wx.BDIAGONAL_HATCH
wx.CROSSDIAG_HATCH
wx.FDIAGONAL_HATCH
wx.CROSS_HATCH
wx.HORIZONTAL_HATCH
wx.VERTICAL_HATCH
wx.TRANSPARENT

wxPython has a number of functions that facilitate drawing different shapes, text and image.

S.N. Functions & Description
1

DrawRectangle()

Draws a rectangle of given dimensions
2

DrawCircle()

Draws a circle at the given point as center and radius
3

DrawEllipse()

Draws an ellipse with the given x and y radius
4

DrawLine()

Draws a line beween two wx.Point objects
5

DrawBitmap()

Draw an image at the given position
6

DrawText()

Displays the given text at the specified position

Example

The above functions are implemented in the following example, making use of Pen, Brush, Colour and Font objects.

The complete code is as follows −

import wx 
 
class Mywin(wx.Frame): 
            
   def __init__(self, parent, title): 
      super(Mywin, self).__init__(parent, title = title,size = (500,300))  
      self.InitUI() 
         
   def InitUI(self): 
      self.Bind(wx.EVT_PAINT, self.OnPaint) 
      self.Centre() 
      self.Show(True)
		
   def OnPaint(self, e): 
      dc = wx.PaintDC(self) 
      brush = wx.Brush("white")  
      dc.SetBackground(brush)  
      dc.Clear() 
        
      dc.DrawBitmap(wx.Bitmap("python.jpg"),10,10,True) 
      color = wx.Colour(255,0,0)
      b = wx.Brush(color) 
		
      dc.SetBrush(b) 
      dc.DrawCircle(300,125,50) 
      dc.SetBrush(wx.Brush(wx.Colour(255,255,255))) 
      dc.DrawCircle(300,125,30) 
		
      font = wx.Font(18, wx.ROMAN, wx.ITALIC, wx.NORMAL) 
      dc.SetFont(font) 
      dc.DrawText("Hello wxPython",200,10) 
		
      pen = wx.Pen(wx.Colour(0,0,255)) 
      dc.SetPen(pen) 
      dc.DrawLine(200,50,350,50) 
      dc.SetBrush(wx.Brush(wx.Colour(0,255,0), wx.CROSS_HATCH)) 
      dc.DrawRectangle(380, 15, 90, 60) 
		
ex = wx.App() 
Mywin(None,'Drawing demo') 
ex.MainLoop()

The above code produces the following output −