Save the contents of a Gtk.DrawingArea or Cairo pattern to an image on disk

Question

I\'ve got a small PyGI project which uses a Cairo image surface, which I then scale with a surface pattern and render on a Gtk.DrawingArea.

I\'d like to write the

Answer 1

Ok, I found a way:

Remembering that Gtk.DrawingArea derives from Gtk.Window, I could use the Gdk.pixbuf_get_from_window() function to get the contents of the drawing area into a GdkPixbuf.Pixbuf and then use the GdkPixbuf.Pixbuf.savev() function to write the pixbuf as an image on disk.

def drawing_area_write(self):
    # drawingarea1 is a Gtk.DrawingArea
    window = self.ui.drawingarea1.get_window()

    # Some code to get the coordinates for the image, which is centered in the
    # in the drawing area. You can ignore it for the purpose of this example
    src_x, src_y = self.get_centered_coordinates(self.ui.drawingarea1,
                                                 self.surface)
    image_height = self.surface.get_height() * self.scale_factor
    image_width = self.surface.get_width() * self.scale_factor

    # Fetch what we rendered on the drawing area into a pixbuf
    pixbuf = Gdk.pixbuf_get_from_window(window, src_x, src_y,
                                      image_width, image_height)

    # Write the pixbuf as a PNG image to disk
    pixbuf.savev('/tmp/testimage.png', 'png', [], [])

While this works, it'd still be nice to see if someone could confirm this is the right way or to see if there is any other alternative.

Answer 2

I found another approach, using the Cairo context passed to the handler of draw events, but it resulted in capturing a region of the parent window that was larger than the DrawingArea.

What worked for me was to use the PixBuf as you have shown, but first calling the queue_draw() method for the DrawingArea, to force a full rendering, and waiting for the event to be processed (easy enough, I already had a draw handler). Otherwise, the resulting images can be partially undrawn.