forked from OpenPDU/openpdu-libs
41 lines
1.4 KiB
Python
41 lines
1.4 KiB
Python
|
# -*- coding: utf-8 -*-
|
||
|
|
# Copyright (c) 2016 Richard Hull and contributors
|
||
|
|
# See LICENSE.rst for details.
|
||
|
|
|
||
|
|
from PIL import Image, ImageDraw
|
||
|
|
|
||
|
|
|
||
|
|
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
|