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latex2png.py
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latex2png.py
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# mostly taken from http://code.google.com/p/latexmath2png/
# install preview.sty
import os
import re
import sys
import io
import glob
import tempfile
import shlex
import subprocess
import traceback
from PIL import Image
class Latex:
BASE = r'''
\documentclass[varwidth]{standalone}
\usepackage{fontspec,unicode-math}
\usepackage[active,tightpage,displaymath,textmath]{preview}
\setmathfont{%s}
\begin{document}
\thispagestyle{empty}
%s
\end{document}
'''
def __init__(self, math, dpi=250, font='Latin Modern Math'):
'''takes list of math code. `returns each element as PNG with DPI=`dpi`'''
self.math = math
self.dpi = dpi
self.font = font
self.prefix_line = self.BASE.split("\n").index(
"%s") # used for calculate error formula index
def write(self, return_bytes=False):
# inline = bool(re.match('^\$[^$]*\$$', self.math)) and False
try:
workdir = tempfile.gettempdir()
fd, texfile = tempfile.mkstemp('.tex', 'eq', workdir, True)
# print(self.BASE % (self.font, self.math))
with os.fdopen(fd, 'w+') as f:
document = self.BASE % (self.font, '\n'.join(self.math))
# print(document)
f.write(document)
png, error_index = self.convert_file(
texfile, workdir, return_bytes=return_bytes)
return png, error_index
finally:
if os.path.exists(texfile):
try:
os.remove(texfile)
except PermissionError:
pass
def convert_file(self, infile, workdir, return_bytes=False):
infile = infile.replace('\\', '/')
try:
# Generate the PDF file
# not stop on error line, but return error line index,index start from 1
cmd = 'xelatex -interaction nonstopmode -file-line-error -output-directory %s %s' % (
workdir.replace('\\', '/'), infile)
p = subprocess.Popen(
shlex.split(cmd),
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
universal_newlines=True
)
sout, serr = p.communicate()
# extract error line from sout
error_index, _ = extract(text=sout, expression=r"%s:(\d+)" % os.path.basename(infile))
# extract success rendered equation
if error_index != []:
# offset index start from 0, same as self.math
error_index = [int(_)-self.prefix_line-1 for _ in error_index]
# Convert the PDF file to PNG's
pdffile = infile.replace('.tex', '.pdf')
result, _ = extract(
text=sout, expression="Output written on %s \((\d+)? page" % pdffile)
if int(result[0]) != len(self.math):
raise Exception('xelatex rendering error, generated %d formula\'s page, but the total number of formulas is %d.' % (
int(result[0]), len(self.math)))
pngfile = os.path.join(workdir, infile.replace('.tex', '.png'))
cmd = 'convert -density %i -colorspace gray %s -quality 90 %s' % (
self.dpi,
pdffile,
pngfile,
) # -bg Transparent -z 9
if sys.platform == 'win32':
cmd = 'magick ' + cmd
p = subprocess.Popen(
shlex.split(cmd),
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
)
sout, serr = p.communicate()
if p.returncode != 0:
raise Exception('PDFpng error', serr, cmd, os.path.exists(
pdffile), os.path.exists(infile))
if return_bytes:
if len(self.math) > 1:
png = [open(pngfile.replace('.png', '')+'-%i.png' %
i, 'rb').read() for i in range(len(self.math))]
else:
png = [open(pngfile.replace(
'.png', '')+'.png', 'rb').read()]
else:
# return path
if len(self.math) > 1:
png = [(pngfile.replace('.png', '')+'-%i.png' % i)
for i in range(len(self.math))]
else:
png = [(pngfile.replace('.png', '')+'.png')]
return png, error_index
except Exception as e:
print(e)
finally:
# Cleanup temporaries
basefile = infile.replace('.tex', '')
tempext = ['.aux', '.pdf', '.log']
if return_bytes:
ims = glob.glob(basefile+'*.png')
for im in ims:
os.remove(im)
for te in tempext:
tempfile = basefile + te
if os.path.exists(tempfile):
os.remove(tempfile)
__cache = {}
def tex2png(eq, **kwargs):
if not eq in __cache:
__cache[eq] = Latex(eq, **kwargs).write(return_bytes=True)
return __cache[eq]
def tex2pil(tex, return_error_index=False, **kwargs):
pngs, error_index = Latex(tex, **kwargs).write(return_bytes=True)
images = [Image.open(io.BytesIO(d)) for d in pngs]
return (images, error_index) if return_error_index else images
def extract(text, expression=None):
"""extract text from text by regular expression
Args:
text (str): input text
expression (str, optional): regular expression. Defaults to None.
Returns:
str: extracted text
"""
try:
pattern = re.compile(expression)
results = re.findall(pattern, text)
return results, True if len(results) != 0 else False
except Exception:
traceback.print_exc()
if __name__ == '__main__':
if len(sys.argv) > 1:
src = sys.argv[1]
else:
src = r'\begin{equation}\mathcal{ L}\nonumber\end{equation}'
print('Equation is: %s' % src)
print(Latex(src).write())