Lazily detect tainted canvas

src/ol/style/IconImage.js

@@ -78,26 +78,28 @@ class IconImage extends EventTarget {
 
     /**
      * @private
-     * @type {boolean}
+     * @type {boolean|undefined}
      */
-    this.tainting_ = false;
-    if (this.imageState_ == ImageState.LOADED) {
-      this.determineTainting_();
-    }
+    this.tainted_;
 
   }
 
   /**
    * @private
+   * @return {boolean} The image canvas is tainted.
    */
-  determineTainting_() {
-    const context = createCanvasContext2D(1, 1);
-    try {
-      context.drawImage(this.image_, 0, 0);
-      context.getImageData(0, 0, 1, 1);
-    } catch (e) {
-      this.tainting_ = true;
+  isTainted_() {
+    if (this.tainted_ === undefined && this.imageState_ === ImageState.LOADED) {
+      this.tainted_ = false;
+      const context = createCanvasContext2D(1, 1);
+      try {
+        context.drawImage(this.image_, 0, 0);
+        context.getImageData(0, 0, 1, 1);
+      } catch (e) {
+        this.tainted_ = true;
+      }
     }
+    return this.tainted_ === true;
   }
 
   /**
@@ -127,7 +129,6 @@ class IconImage extends EventTarget {
     }
     this.size_ = [this.image_.width, this.image_.height];
     this.unlistenImage_();
-    this.determineTainting_();
     this.replaceColor_();
     this.dispatchChangeEvent_();
   }
@@ -153,7 +154,7 @@ class IconImage extends EventTarget {
    */
   getHitDetectionImage(pixelRatio) {
     if (!this.hitDetectionImage_) {
-      if (this.tainting_) {
+      if (this.isTainted_()) {
         const width = this.size_[0];
         const height = this.size_[1];
         const context = createCanvasContext2D(width, height);
@@ -204,7 +205,7 @@ class IconImage extends EventTarget {
    * @private
    */
   replaceColor_() {
-    if (this.tainting_ || this.color_ === null) {
+    if (!this.color_ || this.isTainted_()) {
       return;
     }