Merge pull request #5 from pkra/scale

[feature] scale option

Author: pkra

README.md

@@ -14,8 +14,12 @@ to install mathjax-node-svg2png and its dependencies.
 
 ## Use
 
-This module is used like mathjax-node, extending the input `data` object with a new option
+This module is used like mathjax-node, extending the input `data` object with new options
 
-    png: false,               // enable PNG generation
+   png: false              // enable PNG generation
+   scale: 1                // scaling factor to apply during conversion
 
-Similarly, mathjax-node's `result` object is extended with a new key `png` containing the resulting data-uri string.
+Similarly, mathjax-node's `result` object is extended with new keys `png` (containing the resulting data-uri string) and `pngWidth` (PNG width in pixel).
+
+    png:                   // PNG results
+    pngWidth:              // width (in pixel)

lib/main.js

@@ -34,26 +34,32 @@ var svg2png = require('svg2png');
 // input `data` extends mathjax-node input `data`.
 // Additional values are:
 //
-// png: false,               // enable PNG generation
+// png: false         // enable PNG generation
+// scale: 1,         // scaling factor to apply during conversion
 
 // `result` data extends the mathjax-node `result` data.
 // Additional values are
 //
-// png:                      // PNG as data-uri
+//  png             // data URI in base64
+//  pngWidth        // PNG width (in pixel)
+//
 
 exports.typeset = function(data, callback) {
     if (data.png) data.svg = true;
     mathjax.typeset(data, function(result) {
         if (result.error) callback(result);
-        if (data.png) convert(result, callback);
+        if (data.png) convert(result, data, callback);
     });
 };
 
-var convert = function(result, callback) {
+var convert = function(result, data, callback) {
     var sourceBuffer = new Buffer(result.svg, "utf-8");
+    var scale = data.scale || 1;
+    // NOTE magic constant, vaguely matches ~16pt Times
+    const EXTOPX = data.ex || 6;
+    result.pngWidth = result.width.substring(0, result.width.length - 2) * EXTOPX * scale;
     var returnBuffer = svg2png.sync(sourceBuffer, {
-        width: result.width,
-        height: result.height
+        width: result.pngWidth
     });
     result.png = "data:image/png;base64," + returnBuffer.toString('base64');
     callback(result);

package.json

@@ -1,6 +1,6 @@
 {
   "name": "mathjax-node-svg2png",
-  "version": "1.0.2",
+  "version": "1.1.0",
   "description": "Extend mathjax-node using svg2png",
   "main": "./lib/main.js",
   "scripts": {

test/helper.js

@@ -0,0 +1,11 @@
+// Helpers (for debugging)
+
+var fs = require("fs");
+// writePNG
+// USE: require('./helper.js').writePNG(result.png.data,'out.png');
+exports.writePNG = function (string, filename) {
+    var raw = string.substring(22);
+    fs.writeFile(filename, raw, 'base64', function(err) {
+    if (err) console.log('Error writing to disk' + err);
+    });
+}

test/scale.js

@@ -0,0 +1,16 @@
+var tape = require('tape');
+var typeset = require("../lib/main.js").typeset;
+tape('scaling: basic check', function(t) {
+    t.plan(1);
+    var opt1 = {math: '\\sin(x)', format:'TeX', png:true};
+    var opt2 = {math: '\\sin(x)', format:'TeX', png:true, scale: 3};
+    var result1 = 0;
+    var result2 = 0;
+    typeset(opt1, function (result) {
+        result1 = result.pngWidth;
+    });
+    typeset(opt2, function (result) {
+        result2 = result.pngWidth;
+        t.equal(result1*3, result2, 'Scale applied')
+    });
+});