optimize update of mapbox image source

src/plots/mapbox/layers.js

@@ -38,6 +38,8 @@ proto.update = function update(opts) {
         // IMPORTANT: must create source before layer to not cause errors
         this.updateSource(opts);
         this.updateLayer(opts);
+    } else if(this.needsNewImage(opts)) {
+        this.updateImage(opts);
     } else if(this.needsNewSource(opts)) {
         // IMPORTANT: must delete layer before source to not cause errors
         this.removeLayer();
@@ -52,6 +54,18 @@ proto.update = function update(opts) {
     this.visible = isVisible(opts);
 };
 
+proto.needsNewImage = function(opts) {
+    var map = this.subplot.map;
+    return (
+        map.getSource(this.idSource) &&
+        this.sourceType === 'image' &&
+        opts.sourcetype === 'image' &&
+        (this.source !== opts.source ||
+            JSON.stringify(this.coordinates) !==
+            JSON.stringify(opts.coordinates))
+    );
+};
+
 proto.needsNewSource = function(opts) {
     // for some reason changing layer to 'fill' or 'symbol'
     // w/o changing the source throws an exception in mapbox-gl 0.18 ;
@@ -70,6 +84,13 @@ proto.needsNewLayer = function(opts) {
     );
 };
 
+proto.updateImage = function(opts) {
+    var map = this.subplot.map;
+    map.getSource(this.idSource).updateImage({
+        url: opts.source, coordinates: opts.coordinates
+    });
+};
+
 proto.updateSource = function(opts) {
     var map = this.subplot.map;
 
@@ -223,6 +244,11 @@ function convertOpts(opts) {
                 'text-opacity': opts.opacity
             });
             break;
+        case 'raster':
+            Lib.extendFlat(paint, {
+                'raster-fade-duration': 0
+            });
+            break;
     }
 
     return {