# -*- coding: utf-8 -*-
# Copyright (c) 2017-2022 Richard Hull and contributors
# See LICENSE.rst for details.
from PIL import Image, ImageDraw
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 `generally` treated as
white when displayed on monochrome devices. 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.
If a ``background`` parameter is provided, the canvas is based on the given
background. This is useful to e.g. write text on a given background image.
def __init__(self, device, background=None, dither=False):
self.draw = None
if background is None:
self.image = Image.new("RGB" if dither else device.mode, device.size)
assert background.size == device.size
self.image = background.copy()
self.device = device
self.dither = dither
self.draw = ImageDraw.Draw(self.image)
def __exit__(self, type, value, traceback):
if type is None:
self.image = self.image.convert(self.device.mode)
# do the drawing onto the device
del self.draw # Tidy up the resources
return False # Never suppress exceptions