Initial commit

.gitignore

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+node_modules/
+temp/
+output/

app.js

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+var fs = require('fs');
+var shell = require('shelljs');
+
+var express = require('express');
+
+var port = 3001;
+
+var staticDir = 'static/';
+var tempDirRoot = 'temp/';
+var outputDir = 'output/';
+var httpOutputURL = 'https://latex2image.joeraut.com/output/';
+
+// Command to compile .tex file to .dvi file. Timeout kills LaTeX after 5 seconds if held up
+var latexCMD = 'timeout 5 latex -interaction nonstopmode -halt-on-error equation.tex';
+
+// Command to convert .dvi to .svg file
+var dvisvgmCMD = 'dvisvgm --no-fonts --scale=OUTPUT_SCALE --exact equation.dvi';
+
+var dockerImageName = 'blang/latex:ubuntu'; // https://github.com/blang/latex-docker
+
+// Command to run the above commands in a new Docker container (with LaTeX preinstalled)
+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} && ${dvisvgmCMD}"`;
+
+// Commands to convert .svg to .png/.jpg and compress
+var svgToImageCMD = 'svgexport SVG_FILE_NAME OUT_FILE_NAME';
+var imageMinCMD = 'imagemin IN_FILE_NAME > OUT_FILE_NAME';
+
+// Checklist of valid formats and scales, to verify form values are correct
+var validFormats = ['SVG', 'PNG', 'JPG'];
+var validScales = ['10%', '25%', '50%', '75%', '100%', '125%', '150%', '200%', '500%', '1000%'];
+// Percentage scales mapped to floating point values used in arguments
+var validScalesInternal = ['0.1', '0.25', '0.5', '0.75', '1.0', '1.25', '1.5', '2.0', '5.0', '10.0'];
+
+var fontSize = 12;
+
+// LaTeX document template
+var preamble = `
+\\usepackage{amsmath}
+\\usepackage{amssymb}
+\\usepackage{amsfonts}
+`;
+
+var documentTemplate = `
+\\documentclass[${fontSize}pt]{article}
+${preamble}
+\\thispagestyle{empty}
+\\begin{document}
+\\[
+EQUATION
+\\]
+\\end{document}`;
+
+// Create temp and output directories on first run
+if (!fs.existsSync(tempDirRoot)) {
+    fs.mkdirSync(tempDirRoot);
+}
+if (!fs.existsSync(outputDir)) {
+    fs.mkdirSync(outputDir);
+}
+
+var app = express();
+
+var bodyParser = require('body-parser');
+app.use(bodyParser.json());
+app.use(bodyParser.urlencoded({extended: true}));
+
+// Allow static html files and output files to be accessible
+app.use('/', express.static(staticDir));
+app.use('/output', express.static(outputDir));
+
+// POST call for LaTeX to image conversion. Convert and return image URL or error message
+app.post('/convert', function (req, res) {
+    // Ensure valid inputs
+    if (req.body.latexInput) {
+        if (validScales.includes(req.body.outputScale)) {
+            if (validFormats.includes(req.body.outputFormat)) {
+                var id = generateID(); // Generate unique ID for filename
+
+                shell.mkdir(`${tempDirRoot}${id}`);
+
+                var document = documentTemplate.replace('EQUATION', req.body.latexInput);
+                fs.writeFileSync(`${tempDirRoot}${id}/equation.tex`, document); // Write generated .tex file
+
+                var result = {};
+
+                var finalDockerCMD = dockerCMD.replace('TEMP_DIR_NAME', `${tempDirRoot}${id}`);
+                finalDockerCMD = finalDockerCMD.replace('OUTPUT_SCALE', validScalesInternal[validScales.indexOf(req.body.outputScale)]);
+
+                var fileFormat = req.body.outputFormat.toLowerCase();
+
+                // Asynchronously compile and render the LaTeX to svg
+                shell.exec(finalDockerCMD, {async: true}, function() {
+                    if (fs.existsSync(`${tempDirRoot}${id}/equation.svg`)) {
+                        if (fileFormat === 'svg') { // Converting to SVG, no further processing required
+                            shell.cp(`${tempDirRoot}${id}/equation.svg`, `${outputDir}img-${id}.svg`);
+                            result.imageURL = `${httpOutputURL}img-${id}.svg`;
+                        } else {
+
+                            // Convert svg to png/jpg
+                            var finalSvgToImageCMD = svgToImageCMD.replace('SVG_FILE_NAME', `${tempDirRoot}${id}/equation.svg`);
+                            finalSvgToImageCMD = finalSvgToImageCMD.replace('OUT_FILE_NAME', `${tempDirRoot}${id}/equation.${fileFormat}`);
+                            if (fileFormat === 'jpg') { // Add a white background for jpg images
+                                finalSvgToImageCMD += ' "svg {background: white}"';
+                            }
+                            shell.exec(finalSvgToImageCMD);
+
+                            // Compress the resultant image
+                            var finalImageMinCMD = imageMinCMD.replace('IN_FILE_NAME', `${tempDirRoot}${id}/equation.${fileFormat}`);
+                            finalImageMinCMD = finalImageMinCMD.replace('OUT_FILE_NAME', `${tempDirRoot}${id}/equation_compressed.${fileFormat}`);
+                            shell.exec(finalImageMinCMD);
+
+                            // Final image
+                            shell.cp(`${tempDirRoot}${id}/equation_compressed.${fileFormat}`, `${outputDir}img-${id}.${fileFormat}`);
+
+                            result.imageURL = `${httpOutputURL}img-${id}.${fileFormat}`;
+                        }
+                    } else {
+                        result.error = 'Error converting LaTeX to image. Please ensure the input is valid.';
+                    }
+
+                    shell.rm('-r', `${tempDirRoot}${id}`); // Delete temporary files for this conversion
+
+                    res.end(JSON.stringify(result));
+                });
+
+            } else {
+                res.end(JSON.stringify({error: 'Invalid image format'}));
+            }
+        } else {
+            res.end(JSON.stringify({error: 'Invalid scale'}));
+        }
+    } else {
+        res.end(JSON.stringify({error: 'No LaTeX input provided'}));
+    }
+});
+
+// Start the server
+app.listen(port, function() {
+    console.log(`Latex2image listening on port ${port}`);
+});
+
+
+function generateID() { // Generate a random 16-char hexadecimal ID
+	var output = '';
+	for (var i = 0; i < 16; i++) {
+		output += '0123456789abcdef'.charAt(Math.floor(Math.random() * 16));
+	}
+
+	return output;
+}