86 lines
2.6 KiB
Python
86 lines
2.6 KiB
Python
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""" Image format handling class
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This module contains the image format handler :py:class:`EscposImage`.
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The class is designed to efficiently delegate image processing to
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PIL, rather than spend CPU cycles looping over pixels.
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:author: `Michael Billington <michael.billington@gmail.com>`_
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:organization: `python-escpos <https://github.com/python-escpos>`_
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:copyright: Copyright (c) 2016 Michael Billington <michael.billington@gmail.com>
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:license: GNU GPL v3
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"""
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from PIL import Image, ImageOps
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class EscposImage(object):
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def __init__(self, img_source):
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"""
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Load in an image
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:param img_source: PIL.Image, or filename to load one from.
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"""
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if isinstance(img_source, Image.Image):
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img_original = img_source
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else:
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img_original = Image.open(img_source)
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# Convert to white RGB background, paste over white background
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# to strip alpha.
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img_original = img_original.convert('RGBA')
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im = Image.new("RGB", img_original.size, (255, 255, 255))
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im.paste(img_original, mask=img_original.split()[3])
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# Convert down to greyscale
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im = im.convert("L")
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# Invert: Only works on 'L' images
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im = ImageOps.invert(im)
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# Pure black and white
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self._im = im.convert("1")
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@property
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def width(self):
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"""
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Width of image in pixels
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"""
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width_pixels, _ = self._im.size
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return width_pixels
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@property
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def width_bytes(self):
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"""
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Width of image if you use 8 pixels per byte and 0-pad at the end.
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"""
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return (self.width + 7) >> 3
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@property
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def height(self):
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"""
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Height of image in pixels
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"""
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_, height_pixels = self._im.size
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return height_pixels
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def to_column_format(self, high_density_vertical = True):
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"""
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Extract slices of an image as equal-sized blobs of column-format data.
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:param high_density_vertical: Printed line height in dots
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"""
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im = self._im.transpose(Image.ROTATE_270).transpose(Image.FLIP_LEFT_RIGHT)
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line_height = 24 if high_density_vertical else 8
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width_pixels, height_pixels = im.size
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top = 0
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left = 0
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while left < width_pixels:
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box = (left, top, left + line_height, top + height_pixels)
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im_slice = im.transform((line_height, height_pixels), Image.EXTENT, box)
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im_bytes = im_slice.tobytes()
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yield(im_bytes)
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left += line_height
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def to_raster_format(self):
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"""
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Convert image to raster-format binary
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"""
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return self._im.tobytes()
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