_fileRepresentationMapping = {
'.png': NSPNGFileType,
'.gif': NSGIFFileType,
'.jpg': NSJPEGFileType,
'.jpeg': NSJPEGFileType,
'.bmp': NSBMPFileType,
'.tif': NSTIFFFileType,
'.tiff': NSTIFFFileType,
}


def _getFileRepresentationType(filepath):
	base, ext = os.path.splitext(filepath)
	return _fileRepresentationMapping[ext.lower()]

def screenshot(self, filepath):
	# Take screenshot
	rect = NSScreen.mainScreen().frame()
    	image = NSImage.alloc().initWithSize_((rect.size.width, rect.size.height))
	window = NSWindow.alloc().initWithContentRect_styleMask_backing_defer_(
        				rect, 
            				NSBorderlessWindowMask, 
            				NSBackingStoreNonretained, 
            				False)
	view = NSView.alloc().initWithFrame_(rect)
	window.setLevel_(NSScreenSaverWindowLevel + 100)
	window.setHasShadow_(False)
	window.setAlphaValue_(0.0)
	window.setContentView_(view)
	window.orderFront_(self)
	view.lockFocus()
	screenRep= NSBitmapImageRep.alloc().initWithFocusedViewRect_(rect)
	image.addRepresentation_(screenRep)
	view.unlockFocus()
	window.orderOut_(self)
	window.close()
	    
	rect = NSScreen.mainScreen().frame()
	image = NSImage.alloc().initWithSize_((rect.size.width, rect.size.height))
	screenRep = NSBitmapImageRep.alloc().initWithFocusedViewRect_(rect)
	image.addRepresentation_(screenRep)

	# Save
	representation = _getFileRepresentationType(filepath)
	data = image_rep.representationUsingType_properties_(representation, None)
	data.writeToFile_atomically_(filepath, False)