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Restore special casing of grayscale images in PostScript backend. #12871

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Restore special casing of grayscale images in PostScript backend. #12871

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43 changes: 15 additions & 28 deletions lib/matplotlib/backends/backend_ps.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,6 @@
A PostScript backend, which can produce both PostScript .ps and .eps.
"""

import binascii
import datetime
import glob
from io import StringIO, TextIOWrapper
Expand All @@ -13,6 +12,7 @@
import shutil
import subprocess
from tempfile import TemporaryDirectory
import textwrap
import time

import numpy as np
Expand Down Expand Up @@ -392,26 +392,8 @@ def _get_font_ttf(self, prop):
font.set_size(size, 72.0)
return font

def _rgb(self, rgba):
h, w = rgba.shape[:2]
rgb = rgba[::-1, :, :3]
return h, w, rgb.tostring()

def _hex_lines(self, s, chars_per_line=128):
s = binascii.b2a_hex(s)
nhex = len(s)
lines = []
for i in range(0, nhex, chars_per_line):
limit = min(i+chars_per_line, nhex)
lines.append(s[i:limit])
return lines

def get_image_magnification(self):
"""
Get the factor by which to magnify images passed to draw_image.
Allows a backend to have images at a different resolution to other
artists.
"""
# docstring inherited
return self.image_magnification

def option_scale_image(self):
Expand All @@ -422,17 +404,22 @@ def option_image_nocomposite(self):
# docstring inherited
return not rcParams['image.composite_image']

def _get_image_h_w_bits_command(self, im):
h, w, bits = self._rgb(im)
imagecmd = "false 3 colorimage"

return h, w, bits, imagecmd

def draw_image(self, gc, x, y, im, transform=None):
# docstring inherited

h, w, bits, imagecmd = self._get_image_h_w_bits_command(im)
hexlines = b'\n'.join(self._hex_lines(bits)).decode('ascii')
h, w = im.shape[:2]
if ((im[..., 3] == 255).all()
and (im[..., 0] == im[..., 1]).all()
and (im[..., 0] == im[..., 2]).all()):
data = im[::-1, ..., 0]
imagecmd = "image"
else:
data = im[::-1, :, :3]
imagecmd = "false 3 colorimage"

# data.tobytes().hex() has no spaces, so can be linewrapped by relying
# on textwrap.fill breaking long words.
hexlines = textwrap.fill(data.tobytes().hex(), 128)

if transform is None:
matrix = "1 0 0 1 0 0"
Expand Down