[cairo] Slow drawing

[Drake Miller]

Hello,

I'm drawing an image in gtk.window drawing event
And it's using a lot of CPU Usage.
Here's my method (Vala):
-------------
var img = new Cairo.ImageSurface.from_png("location/image.png");
var pat = new Cairo.Pattern.for_surface(img);
cr.set_source(pat);
cr.rectangle(0, 0, Screen.get_default().width(),120);
cr.clip ();
cr.paint();
----------------------------
When I draw with this method it takes 30% of CPU
Is there anyway faster than this?

Thanks !