Add ol.Image class

src/ol/image.js

@@ -0,0 +1,173 @@
+goog.provide('ol.Image');
+goog.provide('ol.ImageState');
+
+goog.require('goog.array');
+goog.require('goog.events');
+goog.require('ol.Extent');
+
+
+/**
+ * @enum {number}
+ */
+ol.ImageState = {
+  IDLE: 0,
+  LOADING: 1,
+  LOADED: 2,
+  ERROR: 3
+};
+
+
+
+/**
+ * @constructor
+ * @param {ol.Extent} extent Extent.
+ * @param {number} resolution Resolution.
+ * @param {string} src Image source URI.
+ * @param {?string} crossOrigin Cross origin.
+ */
+ol.Image = function(extent, resolution, src, crossOrigin) {
+
+  /**
+   * @private
+   * @type {ol.Extent}
+   */
+  this.extent_ = extent;
+
+  /**
+   * @private
+   * @type {string}
+   */
+  this.src_ = src;
+
+  /**
+   * @private
+   * @type {number}
+   */
+  this.resolution_ = resolution;
+
+  /**
+   * @private
+   * @type {Image}
+   */
+  this.image_ = new Image();
+  if (!goog.isNull(crossOrigin)) {
+    this.image_.crossOrigin = crossOrigin;
+  }
+
+  /**
+   * @private
+   * @type {Object.<number, Image>}
+   */
+  this.imageByContext_ = {};
+
+  /**
+   * @private
+   * @type {Array.<number>}
+   */
+  this.imageListenerKeys_ = null;
+
+  /**
+   * @protected
+   * @type {ol.ImageState}
+   */
+  this.state = ol.ImageState.IDLE;
+};
+
+
+/**
+ * @return {ol.Extent} Extent.
+ */
+ol.Image.prototype.getExtent = function() {
+  return this.extent_;
+};
+
+
+/**
+ * @param {Object=} opt_context Object.
+ * @return {HTMLCanvasElement|Image|HTMLVideoElement} Image.
+ */
+ol.Image.prototype.getImageElement = function(opt_context) {
+  if (goog.isDef(opt_context)) {
+    var image;
+    var key = goog.getUid(opt_context);
+    if (key in this.imageByContext_) {
+      return this.imageByContext_[key];
+    } else if (goog.object.isEmpty(this.imageByContext_)) {
+      image = this.image_;
+    } else {
+      image = /** @type {Image} */ (this.image_.cloneNode(false));
+    }
+    this.imageByContext_[key] = image;
+    return image;
+  } else {
+    return this.image_;
+  }
+};
+
+
+/**
+ * @return {number} Resolution.
+ */
+ol.Image.prototype.getResolution = function() {
+  return this.resolution_;
+};
+
+
+/**
+ * @return {ol.ImageState} State.
+ */
+ol.Image.prototype.getState = function() {
+  return this.state;
+};
+
+
+/**
+ * Tracks loading or read errors.
+ *
+ * @private
+ */
+ol.Image.prototype.handleImageError_ = function() {
+  this.state = ol.ImageState.ERROR;
+  this.unlistenImage_();
+};
+
+
+/**
+ * Tracks successful image load.
+ *
+ * @private
+ */
+ol.Image.prototype.handleImageLoad_ = function() {
+  this.state = ol.ImageState.LOADED;
+  this.unlistenImage_();
+};
+
+
+/**
+ * Load not yet loaded URI.
+ */
+ol.Image.prototype.load = function() {
+  if (this.state == ol.ImageState.IDLE) {
+    this.state = ol.ImageState.LOADING;
+    goog.asserts.assert(goog.isNull(this.imageListenerKeys_));
+    this.imageListenerKeys_ = [
+      goog.events.listenOnce(this.image_, goog.events.EventType.ERROR,
+          this.handleImageError_, false, this),
+      goog.events.listenOnce(this.image_, goog.events.EventType.LOAD,
+          this.handleImageLoad_, false, this)
+    ];
+    this.image_.src = this.src_;
+  }
+};
+
+
+/**
+ * Discards event handlers which listen for load completion or errors.
+ *
+ * @private
+ */
+ol.Image.prototype.unlistenImage_ = function() {
+  goog.asserts.assert(!goog.isNull(this.imageListenerKeys_));
+  goog.array.forEach(this.imageListenerKeys_, goog.events.unlistenByKey);
+  this.imageListenerKeys_ = null;
+};