def decreaseBrushSize(self):
        """
        Increases Brush Size, triggered by pressing corresponding key.
        """
        for key in ('W', 'H', 'L'):
            self.options[key] = max(self.options[key] - 1, 0)
        self.setupPreview()

        Increases Brush Size, triggered by pressing corresponding key.
        
editortools/brush.py