lib/utils/images.js: Add convertInlinePNG() method

lib/utils/images.js

@@ -38,7 +38,23 @@ function convertSVGBufferToPNG(buf, dest) {
     });
 }
 
+// Converts a inline data: to png file
+function convertInlinePNG(source, dest) {
+    if (!/^data\:image\/png/.test(source)) return Promise.reject(new Error('Source is not a PNG data-uri'));
+
+    var base64data = source.split('data:image/png;base64,')[1];
+    var buf = new Buffer(base64data, 'base64');
+
+    return fs.writeFile(dest, buf)
+    .then(function() {
+        if (fs.existsSync(dest)) return;
+
+        throw new Error('Error converting '+source+' into '+dest);
+    });
+}
+
 module.exports = {
     convertSVGToPNG: convertSVGToPNG,
-    convertSVGBufferToPNG: convertSVGBufferToPNG
+    convertSVGBufferToPNG: convertSVGBufferToPNG,
+    convertInlinePNG: convertInlinePNG
 };