Thumbnail method for NGL

thumbnail2.js

// These functions pulled out of prototype method, `this` has `stage` attribute

{
  /** Returns a promise that resolves to an Image object/element */
  getImage: function( params ) {
    
    params = Object.assign( { 
      trim: false,
      antialias: true,
      transparent: false }, params );
    
    return this.stage.makeImage(params).then( function( blob ){
                 
      return new Promise( function( resolve, reject ){
                            
        var fr = new FileReader();
            
        var image = new Image();

        image.onload = function() { resolve( this ); }                  

        fr.onload = function() {
          image.src = this.result; 
        }

        fr.readAsDataURL( blob );

      });

    });

  },
  // Pulled out of prototype, assumes `this` has `stage`
  getThumbnail2:  function() {
    
    // Current image
    var currentImage = this.getImage();

    var self = this;
    var viewer = this.stage.viewer;
    var canvas = viewer.renderer.domElement;
    var container = canvas.parentElement;
    var image;

    var cameraState = this.getCameraState();
    var scale = 100 / viewer.height;
    var scaledState = { z: cameraState.z / scale,
                        zoom: cameraState.zoom * scale };

    var restore = function() {

      image && image.remove();
      self.setCameraState( cameraState );
      canvas.style.visibility = "visible";
      viewer.handleResize();

    }

    var thumbnailPromise = currentImage.then( function( img ){
      image = img;
      img.style.position = canvas.style.position = "absolute";
      img.style.top = canvas.style.top = img.style.left = canvas.style.left = "0px";
      img.style["z-index"] = 10;
      container.appendChild(img);
      canvas.style.visibility = "hidden";
      viewer.setSize( 100, 100 );
      self.setCameraState( scaledState );
      viewer.requestRender();        
      return self.getImage();
    });

    thumbnailPromise.then( restore, restore );

    return thumbnailPromise;

  },
  
  getCameraState: function() {
    var camera = this.stage.viewer.camera;
    return {
      z: camera.position.z,
      zoom: camera.zoom
    };
  },

  setCameraState: function( p ){
    var camera = this.stage.viewer.camera;
    camera.position.z = p.z;
    camera.zoom = p.zoom;
  },

}