lib/output/modifiers/inlinePng.js: Add modifier to save inline PNG images

lib/output/modifiers/inlinePng.js

@@ -0,0 +1,47 @@
+var crc = require('crc');
+var path = require('path');
+
+var imagesUtil = require('../../utils/images');
+var fs = require('../../utils/fs');
+var LocationUtils = require('../../utils/location');
+
+var editHTMLElement = require('./editHTMLElement');
+
+/**
+    Convert all inline PNG images to PNG file
+
+    @param {String} rootFolder
+    @param {HTMLDom} $
+    @return {Promise}
+*/
+function inlinePng(rootFolder, currentFile, $) {
+    var currentDirectory = path.dirname(currentFile);
+
+    return editHTMLElement($, 'img', function($img) {
+        var src = $img.attr('src');
+        if (!LocationUtils.isDataURI(src)) {
+            return;
+        }
+
+        // We avoid generating twice the same PNG
+        var hash = crc.crc32(src).toString(16);
+        var fileName = hash + '.png';
+
+        // Result file path
+        var filePath = path.join(rootFolder, fileName);
+
+        return fs.assertFile(filePath, function() {
+            return imagesUtil.convertInlinePNG(src, filePath);
+        })
+        .then(function() {
+            // Convert filename to a relative filename
+            fileName = LocationUtils.relative(currentDirectory, fileName);
+
+            // Replace src
+            $img.attr('src', fileName);
+        });
+    });
+}
+
+
+module.exports = inlinePng;