Added image data value to 'forEachLayerAtPixel' method callback

The update has been added to the docs for all 'forEachLayerAtPixel' definitions
and currently returns null for non-supporting definitions. ol.Color typeDef
was also updated to support Uint8Arrays & Uint8ClampedArrays as it is the
reference type for the addded argument #5586

src/ol/renderer/canvas/imagelayer.js

@@ -69,7 +69,13 @@ ol.renderer.canvas.ImageLayer.prototype.forEachFeatureAtCoordinate = function(co
 
 
 /**
- * @inheritDoc
+ * @param {ol.Pixel} pixel Pixel.
+ * @param {olx.FrameState} frameState FrameState.
+ * @param {function(this: S, ol.layer.Layer, ol.Color): T} callback Layer
+ *     callback.
+ * @param {S} thisArg Value to use as `this` when executing `callback`.
+ * @return {T|undefined} Callback result.
+ * @template S,T,U
  */
 ol.renderer.canvas.ImageLayer.prototype.forEachLayerAtPixel = function(pixel, frameState, callback, thisArg) {
   if (!this.getImage()) {
@@ -85,7 +91,7 @@ ol.renderer.canvas.ImageLayer.prototype.forEachLayerAtPixel = function(pixel, fr
         coordinate, frameState, ol.functions.TRUE, this);
 
     if (hasFeature) {
-      return callback.call(thisArg, this.getLayer());
+      return callback.call(thisArg, this.getLayer(), null);
     } else {
       return undefined;
     }
@@ -108,7 +114,7 @@ ol.renderer.canvas.ImageLayer.prototype.forEachLayerAtPixel = function(pixel, fr
 
     var imageData = this.hitCanvasContext_.getImageData(0, 0, 1, 1).data;
     if (imageData[3] > 0) {
-      return callback.call(thisArg, this.getLayer());
+      return callback.call(thisArg, this.getLayer(),  imageData);
     } else {
       return undefined;
     }

src/ol/renderer/canvas/tilelayer.js

@@ -186,7 +186,13 @@ ol.renderer.canvas.TileLayer.prototype.prepareFrame = function(
 
 
 /**
- * @inheritDoc
+ * @param {ol.Pixel} pixel Pixel.
+ * @param {olx.FrameState} frameState FrameState.
+ * @param {function(this: S, ol.layer.Layer, ol.Color): T} callback Layer
+ *     callback.
+ * @param {S} thisArg Value to use as `this` when executing `callback`.
+ * @return {T|undefined} Callback result.
+ * @template S,T,U
  */
 ol.renderer.canvas.TileLayer.prototype.forEachLayerAtPixel = function(
     pixel, frameState, callback, thisArg) {
@@ -200,7 +206,7 @@ ol.renderer.canvas.TileLayer.prototype.forEachLayerAtPixel = function(
       pixel[0], pixel[1], 1, 1).data;
 
   if (imageData[3] > 0) {
-    return callback.call(thisArg, this.getLayer());
+    return callback.call(thisArg, this.getLayer(),  imageData);
   } else {
     return undefined;
   }