# -*- coding: utf-8 -*-
# Copyright (c) 2016 Richard Hull and contributors
# See LICENSE.rst for details.
from PIL import Image, ImageDraw
[docs]class canvas(object):
"""
A canvas returns a properly-sized :py:mod:`PIL.ImageDraw` object onto
which the caller can draw upon. As soon as the with-block completes, the
resultant image is flushed onto the device.
By default, any color (other than black) will be treated as white and
displayed on the device. However, this behaviour can be changed by adding
``dither=True`` and the image will be converted from RGB space into a 1-bit
monochrome image where dithering is employed to differentiate colors at the
expense of resolution.
"""
def __init__(self, device, dither=False):
self.draw = None
self.image = Image.new("RGB" if dither else device.mode, device.size)
self.device = device
self.dither = dither
def __enter__(self):
self.draw = ImageDraw.Draw(self.image)
return self.draw
def __exit__(self, type, value, traceback):
if type is None:
if self.dither:
self.image = self.image.convert(self.device.mode)
# do the drawing onto the device
self.device.display(self.image)
del self.draw # Tidy up the resources
return False # Never suppress exceptions