Draw image in GTK3

The script shows some techniques in drawing an image using Cairo. The image will be resized correctly even if the dimensions of the window is changed.

1. Define a drawing area using Cairo.
2. Load the image into a pixbuf.
3. Crop and resize the pixbuf.
4. Show the pixbuf on the drawing area.

Source Code

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#!/usr/bin/python # Title : GTK3 Image 01 # Date : 30/10/2014 # Description : # 1. Read an image file (png) and show it on in a window # 2. Fit the image with the width of the window # 3. Resize the image correctly from gi.repository import Gtk, Gdk from gi.repository.GdkPixbuf import Pixbuf, InterpType class mainApp(): def __init__(self): self.win = Gtk.Window() self.win.connect('destroy', Gtk.main_quit) self.win.set_default_size(800,600) self.win.set_position(Gtk.WindowPosition.CENTER) self.win.set_title('GTK3 ImageViewer') mBox = Gtk.VBox(False,2) # not equal height, space # draw area self.drawArea = Gtk.DrawingArea() self.drawArea.connect("draw", self.onDraw) mBox.pack_start(self.drawArea,True,True,2) # message label self.msg = Gtk.Label("Message") mBox.pack_end(self.msg,False,True,2) self.win.add(mBox) self.win.show_all() # load image self.pixbuf = None self.pixbufW = 0 self.pixbufH = 0 self.loadImg2Pixbuf('dice.png') def loadImg2Pixbuf(self, pFile): # - file -> pixbuf self.pixbuf = \ Pixbuf.new_from_file(pFile) self.pixbufW = self.pixbuf.get_width() self.pixbufH = self.pixbuf.get_height() print 'Image Size [W:%d, H:%d]' % (self.pixbufW,self.pixbufH) def onDraw(self, pDrawArea, pCr): #print 'onDraw...' # get the dimensions of the draw area mW = pDrawArea.get_allocated_width()-10 mH = pDrawArea.get_allocated_height()-10 #print '[W:%d, H:%d]' % (mW,mH) # crop original page stored in pixbuf mFac = float(mW)/self.pixbufW # reduction factor mH1 = float(mH)/mFac if mH1 < self.pixbufH: mpixbuf1 = Pixbuf.new_subpixbuf( self.pixbuf,0,0,self.pixbufW,mH1) else: mpixbuf1 = self.pixbuf mH1 = self.pixbufH # resize pixbuf to fit screen dimensions # mquality = # InterpType.NEAREST # fastest, lowest quality # InterpType.BILINEAR # best quality/speed balance # InterpType.HYPER # slowest, highest quality # mquality = InterpType.HYPER mpixbuf2 = Pixbuf.scale_simple( mpixbuf1,mW,mH1*mFac,mquality) # draw pixbuf on screen Gdk.cairo_set_source_pixbuf(pCr, mpixbuf2, 5, 5) pCr.paint() # message mstr1 = 'Image [W:%d, H:%d] ' % (self.pixbufW,self.pixbufH) mstr2 = 'Display [W:%d, H:%d]' % (mW,mH) self.msg.set_text(mstr1+mstr2) mApp = mainApp() Gtk.main()