Initial commit
This commit is contained in:
Joseph Rautenbach
150
app.js
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150
app.js
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var fs = require('fs');
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var shell = require('shelljs');
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var express = require('express');
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var port = 3001;
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var staticDir = 'static/';
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var tempDirRoot = 'temp/';
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var outputDir = 'output/';
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var httpOutputURL = 'https://latex2image.joeraut.com/output/';
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// Command to compile .tex file to .dvi file. Timeout kills LaTeX after 5 seconds if held up
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var latexCMD = 'timeout 5 latex -interaction nonstopmode -halt-on-error equation.tex';
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// Command to convert .dvi to .svg file
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var dvisvgmCMD = 'dvisvgm --no-fonts --scale=OUTPUT_SCALE --exact equation.dvi';
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var dockerImageName = 'blang/latex:ubuntu'; // https://github.com/blang/latex-docker
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// Command to run the above commands in a new Docker container (with LaTeX preinstalled)
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var dockerCMD = `cd TEMP_DIR_NAME && exec docker run --rm -i --user="$(id -u):$(id -g)" --net=none -v "$PWD":/data "${dockerImageName}" /bin/sh -c "${latexCMD} && ${dvisvgmCMD}"`;
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// Commands to convert .svg to .png/.jpg and compress
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var svgToImageCMD = 'svgexport SVG_FILE_NAME OUT_FILE_NAME';
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var imageMinCMD = 'imagemin IN_FILE_NAME > OUT_FILE_NAME';
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// Checklist of valid formats and scales, to verify form values are correct
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var validFormats = ['SVG', 'PNG', 'JPG'];
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var validScales = ['10%', '25%', '50%', '75%', '100%', '125%', '150%', '200%', '500%', '1000%'];
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// Percentage scales mapped to floating point values used in arguments
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var validScalesInternal = ['0.1', '0.25', '0.5', '0.75', '1.0', '1.25', '1.5', '2.0', '5.0', '10.0'];
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var fontSize = 12;
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// LaTeX document template
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var preamble = `
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\\usepackage{amsmath}
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\\usepackage{amssymb}
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\\usepackage{amsfonts}
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`;
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var documentTemplate = `
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\\documentclass[${fontSize}pt]{article}
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${preamble}
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\\thispagestyle{empty}
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\\begin{document}
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\\[
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EQUATION
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\\]
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\\end{document}`;
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// Create temp and output directories on first run
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if (!fs.existsSync(tempDirRoot)) {
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fs.mkdirSync(tempDirRoot);
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}
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if (!fs.existsSync(outputDir)) {
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fs.mkdirSync(outputDir);
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}
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var app = express();
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var bodyParser = require('body-parser');
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app.use(bodyParser.json());
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app.use(bodyParser.urlencoded({extended: true}));
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// Allow static html files and output files to be accessible
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app.use('/', express.static(staticDir));
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app.use('/output', express.static(outputDir));
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// POST call for LaTeX to image conversion. Convert and return image URL or error message
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app.post('/convert', function (req, res) {
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// Ensure valid inputs
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if (req.body.latexInput) {
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if (validScales.includes(req.body.outputScale)) {
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if (validFormats.includes(req.body.outputFormat)) {
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var id = generateID(); // Generate unique ID for filename
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shell.mkdir(`${tempDirRoot}${id}`);
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var document = documentTemplate.replace('EQUATION', req.body.latexInput);
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fs.writeFileSync(`${tempDirRoot}${id}/equation.tex`, document); // Write generated .tex file
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var result = {};
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var finalDockerCMD = dockerCMD.replace('TEMP_DIR_NAME', `${tempDirRoot}${id}`);
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finalDockerCMD = finalDockerCMD.replace('OUTPUT_SCALE', validScalesInternal[validScales.indexOf(req.body.outputScale)]);
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var fileFormat = req.body.outputFormat.toLowerCase();
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// Asynchronously compile and render the LaTeX to svg
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shell.exec(finalDockerCMD, {async: true}, function() {
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if (fs.existsSync(`${tempDirRoot}${id}/equation.svg`)) {
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if (fileFormat === 'svg') { // Converting to SVG, no further processing required
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shell.cp(`${tempDirRoot}${id}/equation.svg`, `${outputDir}img-${id}.svg`);
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result.imageURL = `${httpOutputURL}img-${id}.svg`;
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} else {
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// Convert svg to png/jpg
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var finalSvgToImageCMD = svgToImageCMD.replace('SVG_FILE_NAME', `${tempDirRoot}${id}/equation.svg`);
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finalSvgToImageCMD = finalSvgToImageCMD.replace('OUT_FILE_NAME', `${tempDirRoot}${id}/equation.${fileFormat}`);
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if (fileFormat === 'jpg') { // Add a white background for jpg images
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finalSvgToImageCMD += ' "svg {background: white}"';
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}
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shell.exec(finalSvgToImageCMD);
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// Compress the resultant image
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var finalImageMinCMD = imageMinCMD.replace('IN_FILE_NAME', `${tempDirRoot}${id}/equation.${fileFormat}`);
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finalImageMinCMD = finalImageMinCMD.replace('OUT_FILE_NAME', `${tempDirRoot}${id}/equation_compressed.${fileFormat}`);
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shell.exec(finalImageMinCMD);
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// Final image
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shell.cp(`${tempDirRoot}${id}/equation_compressed.${fileFormat}`, `${outputDir}img-${id}.${fileFormat}`);
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result.imageURL = `${httpOutputURL}img-${id}.${fileFormat}`;
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}
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} else {
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result.error = 'Error converting LaTeX to image. Please ensure the input is valid.';
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}
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shell.rm('-r', `${tempDirRoot}${id}`); // Delete temporary files for this conversion
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res.end(JSON.stringify(result));
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});
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} else {
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res.end(JSON.stringify({error: 'Invalid image format'}));
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}
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} else {
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res.end(JSON.stringify({error: 'Invalid scale'}));
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}
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} else {
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res.end(JSON.stringify({error: 'No LaTeX input provided'}));
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}
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});
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// Start the server
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app.listen(port, function() {
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console.log(`Latex2image listening on port ${port}`);
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});
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function generateID() { // Generate a random 16-char hexadecimal ID
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var output = '';
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for (var i = 0; i < 16; i++) {
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output += '0123456789abcdef'.charAt(Math.floor(Math.random() * 16));
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}
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return output;
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}
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