Merge pull request #4105 from plotly/datauri_images

Process data uri images synchronously

Author: jonmmease

Diff for: src/components/images/draw.js

@@ -74,49 +74,54 @@ module.exports = function draw(gd) {
     function setImage(d) {
         var thisImage = d3.select(this);
 
-        if(this.img && this.img.src === d.source) {
+        if(this._imgSrc === d.source) {
             return;
         }
 
         thisImage.attr('xmlns', xmlnsNamespaces.svg);
 
-        var imagePromise = new Promise(function(resolve) {
-            var img = new Image();
-            this.img = img;
+        if(d.source && d.source.slice(0, 5) === 'data:') {
+            thisImage.attr('xlink:href', d.source);
+            this._imgSrc = d.source;
+        } else {
+            var imagePromise = new Promise(function(resolve) {
+                var img = new Image();
+                this.img = img;
 
-            // If not set, a `tainted canvas` error is thrown
-            img.setAttribute('crossOrigin', 'anonymous');
-            img.onerror = errorHandler;
-            img.onload = function() {
-                var canvas = document.createElement('canvas');
-                canvas.width = this.width;
-                canvas.height = this.height;
+                // If not set, a `tainted canvas` error is thrown
+                img.setAttribute('crossOrigin', 'anonymous');
+                img.onerror = errorHandler;
+                img.onload = function() {
+                    var canvas = document.createElement('canvas');
+                    canvas.width = this.width;
+                    canvas.height = this.height;
 
-                var ctx = canvas.getContext('2d');
-                ctx.drawImage(this, 0, 0);
+                    var ctx = canvas.getContext('2d');
+                    ctx.drawImage(this, 0, 0);
 
-                var dataURL = canvas.toDataURL('image/png');
+                    var dataURL = canvas.toDataURL('image/png');
 
-                thisImage.attr('xlink:href', dataURL);
+                    thisImage.attr('xlink:href', dataURL);
 
-                // resolve promise in onload handler instead of on 'load' to support IE11
-                // see https://github.com/plotly/plotly.js/issues/1685
-                // for more details
-                resolve();
-            };
+                    // resolve promise in onload handler instead of on 'load' to support IE11
+                    // see https://github.com/plotly/plotly.js/issues/1685
+                    // for more details
+                    resolve();
+                };
 
+                thisImage.on('error', errorHandler);
 
-            thisImage.on('error', errorHandler);
+                img.src = d.source;
+                this._imgSrc = d.source;
 
-            img.src = d.source;
-
-            function errorHandler() {
-                thisImage.remove();
-                resolve();
-            }
-        }.bind(this));
+                function errorHandler() {
+                    thisImage.remove();
+                    resolve();
+                }
+            }.bind(this));
 
-        gd._promises.push(imagePromise);
+            gd._promises.push(imagePromise);
+        }
     }
 
     function applyAttributes(d) {

Diff for: test/jasmine/tests/layout_images_test.js

@@ -12,6 +12,10 @@ var mouseEvent = require('../assets/mouse_event');
 var jsLogo = 'https://images.plot.ly/language-icons/api-home/js-logo.png';
 var pythonLogo = 'https://images.plot.ly/language-icons/api-home/python-logo.png';
 
+// Single red pixel png generated with http://png-pixel.com/
+var dataUriImage = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfF' +
+    'cSJAAAADUlEQVR42mP8z8DwHwAFBQIAX8jx0gAAAABJRU5ErkJggg==';
+
 describe('Layout images', function() {
     describe('supplyLayoutDefaults', function() {
         var layoutIn,
@@ -290,6 +294,31 @@ describe('Layout images', function() {
 
         afterEach(destroyGraphDiv);
 
+        it('should only create canvas if url image', function(done) {
+            var originalCreateElement = document.createElement;
+            var newCanvasElement;
+            spyOn(document, 'createElement').and.callFake(function(elementType) {
+                var element = originalCreateElement.call(document, elementType);
+                if(elementType === 'canvas') {
+                    newCanvasElement = element;
+                    spyOn(newCanvasElement, 'toDataURL');
+                }
+                return element;
+            });
+
+            Plotly.relayout(gd, 'images[0].source', dataUriImage)
+            .then(function() {
+                expect(newCanvasElement).toBeUndefined();
+            })
+            .then(function() { return Plotly.relayout(gd, 'images[0].source', jsLogo); })
+            .then(function() {
+                expect(newCanvasElement).toBeDefined();
+                expect(newCanvasElement.toDataURL).toHaveBeenCalledTimes(1);
+            })
+            .catch(failTest)
+            .then(done);
+        });
+
         it('should update the image if changed', function(done) {
             var img = Plotly.d3.select('image');
             var url = img.attr('xlink:href');