Method draw

src/openlayers/overlay/HeatMap.js:230–251

* @function HeatMap.prototype.draw * @description 绘制热点图。 * @param {Array} data - convertToPixelPoints 方法计算出的点。 * @param {number} maxWeight -最大权重。 * @private

(data, maxWeight)

     * @private
     */
    draw(data, maxWeight) {
        if (this.maxHeight > 0 && this.maxWidth > 0) {
            //清空
            var ctx = this.canvasContext;
            this.canvasContext.clearRect(0, 0, this.maxWidth, this.maxHeight);
            this.drawCircle(this.useRadius);
            this.createGradient();

            for (var i = 0; i < data.length; i++) {
                var p = data[i];
                this.canvasContext.globalAlpha = Math.max(p[2] / maxWeight, 0.05);
                this.canvasContext.drawImage(this.circle, p[0] - this.useRadius, p[1] - this.useRadius);
            }

            var colored = ctx.getImageData(0, 0, this.maxWidth, this.maxHeight);
            this.colorize(colored.data, this.grad);
            ctx.putImageData(colored, 0, 0);
        } else {
            return false;
        }

    }

    /**
     * @function HeatMap.prototype.colorize