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88 lines
3.1 KiB
Python
88 lines
3.1 KiB
Python
6 years ago
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#!/usr/bin/env python
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"""
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This is a minimal ESC/POS printing script which uses the 'column format'
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of image output.
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The snippet 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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Do not attempt to use this snippet in production, get a copy of python-escpos instead!
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"""
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from PIL import Image, ImageOps
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import six
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import sys
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import os
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def _to_column_format(im, line_height):
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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 im: Image to extract from
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:param line_height: Printed line height in dots
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"""
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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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blobs = []
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while left < width_pixels:
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remaining_pixels = width_pixels - left
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box = (left, top, left + line_height, top + height_pixels)
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slice = im.transform((line_height, height_pixels), Image.EXTENT, box)
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bytes = slice.tobytes()
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blobs.append(bytes)
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left += line_height
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return blobs
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def _int_low_high(inp_number, out_bytes):
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""" Generate multiple bytes for a number: In lower and higher parts, or more parts as needed.
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:param inp_number: Input number
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:param out_bytes: The number of bytes to output (1 - 4).
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"""
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max_input = (256 << (out_bytes * 8) - 1);
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if not 1 <= out_bytes <= 4:
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raise ValueError("Can only output 1-4 byes")
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if not 0 <= inp_number <= max_input:
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raise ValueError("Number too large. Can only output up to {0} in {1} byes".format(max_input, out_bytes))
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outp = b'';
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for _ in range(0, out_bytes):
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outp += six.int2byte(inp_number % 256)
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inp_number = inp_number // 256
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return outp
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if __name__ == "__main__":
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# Configure
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high_density_horizontal = True
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high_density_vertical = True
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if len(sys.argv) > 1:
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filename = sys.argv[1]
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else:
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filename = u"img.png"
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# Load Image
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im = Image.open(filename)
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# Initial rotate. mirror, and extract blobs for each 8 or 24-pixel row
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# Convert to black & white via greyscale (so that bits can be inverted)
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im = im.convert("L") # Invert: Only works on 'L' images
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im = ImageOps.invert(im) # Bits are sent with 0 = white, 1 = black in ESC/POS
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im = im.convert("1") # Pure black and white
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im = im.transpose(Image.ROTATE_270).transpose(Image.FLIP_LEFT_RIGHT)
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line_height = 3 if high_density_vertical else 1
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blobs = _to_column_format (im, line_height * 8);
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# Generate ESC/POS header and print image
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ESC = b"\x1b";
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# Height and width refer to output size here, image is rotated in memory so coordinates are swapped
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height_pixels, width_pixels = im.size
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density_byte = (1 if high_density_horizontal else 0) + (32 if high_density_vertical else 0);
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header = ESC + b"*" + six.int2byte(density_byte) + _int_low_high( width_pixels, 2 );
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with os.fdopen(sys.stdout.fileno(), 'wb') as fp:
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fp.write(ESC + b"3" + six.int2byte(16)); # Adjust line-feed size
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for blob in blobs:
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fp.write(header + blob + b"\n")
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fp.write(ESC + b"2"); # Reset line-feed size
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