code: function (mode, context) {
              context = context || this.getContext();
              this.currentBlendMode = mode;
              switch (mode) {
                  case "multiply" :
                      context.globalCompositeOperation = "multiply";
                      break;
  
                  default : // normal
                      context.globalCompositeOperation = "source-over";
                      this.currentBlendMode = "normal";
                      break;
              }
  
              // transparent setting will override the given blendmode for this.context
              if (this.settings.doubleBuffering && this.settings.transparent) {
                  // Clears the front buffer for each frame blit
                  this.context.globalCompositeOperation = "copy";
              }
          }
docs: Set a blend mode for the given context
  @name setBlendMode
  @memberOf me.CanvasRenderer.prototype
  @function
  @param {String} [mode="normal"] blend mode : "normal", "multiply"
  @param {Context2d} [context]