A couple of days ago I needed to take screenshots of my linux desktop's screen and manipulate these captured images using Python Image Library (PIL). I wrote a small python class to do the work of taking the screenshot and returning a PIL Image object for use in the rest of the system I was writing.
The code ended up being simpler than I expected, mostly because GDK, the library used as an intermediary between GTK and the low-level window manager and display server commands, does all the heavy lifting.
Method
I wanted to take many screenshots during a run of the program I was writing, so allocated a persistent gtk.gdk.Pixbuf object to store the captured image in. This object has a handy get_from_drawable method. Of course, the X11 root window is a drawable, so by using gtk.gdk.get_default_root_window() we can copy each pixel into our buffer.
Once the Pixbuf is full, an Image needs to be created from it, since that was the original aim. Luckily, there's Image.frombuffer to do all the hard work when combined with Pixbuf.get_pixels().
Full code:
import Image, gtk
class Screenshotter(object):
def __init__(self):
self.img_width = gtk.gdk.screen_width()
self.img_height = gtk.gdk.screen_height()
self.screengrab = gtk.gdk.Pixbuf(
gtk.gdk.COLORSPACE_RGB,
False,
8,
self.img_width,
self.img_height
)
def take(self):
self.screengrab.get_from_drawable(
gtk.gdk.get_default_root_window(),
gtk.gdk.colormap_get_system(),
0, 0, 0, 0,
self.img_width,
self.img_height
)
final_screengrab = Image.frombuffer(
"RGB",
(self.img_width, self.img_height),
self.screengrab.get_pixels(),
"raw",
"RGB",
self.screengrab.get_rowstride(),
1
)
return final_screengrab
if __name__ == '__main__':
screenshot = Screenshotter()
image = screenshot.take()