Support for image or pixel operations

src/ol/raster/operation.js

@@ -1,23 +1,39 @@
 goog.provide('ol.raster.IdentityOp');
 goog.provide('ol.raster.Operation');
+goog.provide('ol.raster.OperationType');
 
 
 /**
- * A function that takes an array of {@link ol.raster.Pixel} as inputs, performs
- * some operation on them, and returns an array of {@link ol.raster.Pixel} as
- * outputs.
+ * Raster operation type. Supported values are `'pixel'` and `'image'`.
+ * @enum {string}
+ * @api
+ */
+ol.raster.OperationType = {
+  PIXEL: 'pixel',
+  IMAGE: 'image'
+};
+
+
+/**
+ * A function that takes an array of input data, performs some operation, and
+ * returns an array of ouput data.  For `'pixel'` type operations, functions
+ * will be called with an array of {@link ol.raster.Pixel} data and should
+ * return an array of the same.  For `'image'` type operations, functions will
+ * be called with an array of {@link ImageData
+ * https://developer.mozilla.org/en-US/docs/Web/API/ImageData} and should return
+ * an array of the same.
  *
- * @typedef {function(Array.<ol.raster.Pixel>): Array.<ol.raster.Pixel>}
+ * @typedef {function((Array.<ol.raster.Pixel>|Array.<ImageData>)):
+ *     (Array.<ol.raster.Pixel>|Array.<ImageData>)}
  * @api
  */
 ol.raster.Operation;
 
 
 /**
- * The identity operation for pixels.  Returns the supplied input pixels as
- * outputs.
- * @param {Array.<ol.raster.Pixel>} inputs Input pixels.
- * @return {Array.<ol.raster.Pixel>} The input pixels as output.
+ * The identity operation.  Returns the supplied input data as output.
+ * @param {(Array.<ol.raster.Pixel>|Array.<ImageData>)} inputs Input data.
+ * @return {(Array.<ol.raster.Pixel>|Array.<ImageData>)} The output data.
  */
 ol.raster.IdentityOp = function(inputs) {
   return inputs;