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node_modules/zrender/src/graphic/helper/image.js 2.78 KB
aaac7fed   liuqimichale   add
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  import LRU from '../../core/LRU';
  
  var globalImageCache = new LRU(50);
  
  /**
   * @param {string|HTMLImageElement|HTMLCanvasElement|Canvas} newImageOrSrc
   * @return {HTMLImageElement|HTMLCanvasElement|Canvas} image
   */
  export function findExistImage(newImageOrSrc) {
      if (typeof newImageOrSrc === 'string') {
          var cachedImgObj = globalImageCache.get(newImageOrSrc);
          return cachedImgObj && cachedImgObj.image;
      }
      else {
          return newImageOrSrc;
      }
  }
  
  /**
   * Caution: User should cache loaded images, but not just count on LRU.
   * Consider if required images more than LRU size, will dead loop occur?
   *
   * @param {string|HTMLImageElement|HTMLCanvasElement|Canvas} newImageOrSrc
   * @param {HTMLImageElement|HTMLCanvasElement|Canvas} image Existent image.
   * @param {module:zrender/Element} [hostEl] For calling `dirty`.
   * @param {Function} [cb] params: (image, cbPayload)
   * @param {Object} [cbPayload] Payload on cb calling.
   * @return {HTMLImageElement|HTMLCanvasElement|Canvas} image
   */
  export function createOrUpdateImage(newImageOrSrc, image, hostEl, cb, cbPayload) {
      if (!newImageOrSrc) {
          return image;
      }
      else if (typeof newImageOrSrc === 'string') {
  
          // Image should not be loaded repeatly.
          if ((image && image.__zrImageSrc === newImageOrSrc) || !hostEl) {
              return image;
          }
  
          // Only when there is no existent image or existent image src
          // is different, this method is responsible for load.
          var cachedImgObj = globalImageCache.get(newImageOrSrc);
  
          var pendingWrap = {hostEl: hostEl, cb: cb, cbPayload: cbPayload};
  
          if (cachedImgObj) {
              image = cachedImgObj.image;
              !isImageReady(image) && cachedImgObj.pending.push(pendingWrap);
          }
          else {
              !image && (image = new Image());
              image.onload = image.onerror = imageOnLoad;
  
              globalImageCache.put(
                  newImageOrSrc,
                  image.__cachedImgObj = {
                      image: image,
                      pending: [pendingWrap]
                  }
              );
  
              image.src = image.__zrImageSrc = newImageOrSrc;
          }
  
          return image;
      }
      // newImageOrSrc is an HTMLImageElement or HTMLCanvasElement or Canvas
      else {
          return newImageOrSrc;
      }
  }
  
  function imageOnLoad() {
      var cachedImgObj = this.__cachedImgObj;
      this.onload = this.onerror = this.__cachedImgObj = null;
  
      for (var i = 0; i < cachedImgObj.pending.length; i++) {
          var pendingWrap = cachedImgObj.pending[i];
          var cb = pendingWrap.cb;
          cb && cb(this, pendingWrap.cbPayload);
          pendingWrap.hostEl.dirty();
      }
      cachedImgObj.pending.length = 0;
  }
  
  export function isImageReady(image) {
      return image && image.width && image.height;
  }