src/chart/heatmap/HeatmapLayer.js
function () {
        var brushCanvas = this._brushCanvas || (this._brushCanvas = zrUtil.createCanvas());
        // set brush size
        var r = this.pointSize + this.blurSize;
        var d = r * 2;
        brushCanvas.width = d;
        brushCanvas.height = d;

        var ctx = brushCanvas.getContext('2d');
        ctx.clearRect(0, 0, d, d);

        // in order to render shadow without the distinct circle,
        // draw the distinct circle in an invisible place,
        // and use shadowOffset to draw shadow in the center of the canvas
        ctx.shadowOffsetX = d;
        ctx.shadowBlur = this.blurSize;
        // draw the shadow in black, and use alpha and shadow blur to generate
        // color in color map
        ctx.shadowColor = '#000';

        // draw circle in the left to the canvas
        ctx.beginPath();
        ctx.arc(-r, r, this.pointSize, 0, Math.PI * 2, true);
        ctx.closePath();
        ctx.fill();
        return brushCanvas;
    }
function () {
        var brushCanvas = this._brushCanvas || (this._brushCanvas = zrUtil.createCanvas());
        // set brush size
        var r = this.pointSize + this.blurSize;
        var d = r * 2;
        brushCanvas.width = d;
        brushCanvas.height = d;

        var ctx = brushCanvas.getContext('2d');
        ctx.clearRect(0, 0, d, d);

        // in order to render shadow without the distinct circle,
        // draw the distinct circle in an invisible place,
        // and use shadowOffset to draw shadow in the center of the canvas
        ctx.shadowOffsetX = d;
        ctx.shadowBlur = this.blurSize;
        // draw the shadow in black, and use alpha and shadow blur to generate
        // color in color map
        ctx.shadowColor = '#000';

        // draw circle in the left to the canvas
        ctx.beginPath();
        ctx.arc(-r, r, this.pointSize, 0, Math.PI * 2, true);
        ctx.closePath();
        ctx.fill();
        return brushCanvas;
    }
function ( ) { var brushCanvas = this . _brushCanvas || ( this . _brushCanvas = zrUtil . createCanvas ( ) ) ; // set brush size var r = this . pointSize + this . blurSize ; var d = r * 2 ; brushCanvas . width = d ; brushCanvas . height = d ; var ctx = brushCanvas . getContext ( '2d' ) ; ctx . clearRect ( 0 , 0 , d , d ) ; // in order to render shadow without the distinct circle, // draw the distinct circle in an invisible place, // and use shadowOffset to draw shadow in the center of the canvas ctx . shadowOffsetX = d ; ctx . shadowBlur = this . blurSize ; // draw the shadow in black, and use alpha and shadow blur to generate // color in color map ctx . shadowColor = '#000' ; // draw circle in the left to the canvas ctx . beginPath ( ) ; ctx . arc ( - r , r , this . pointSize , 0 , Math . PI * 2 , true ) ; ctx . closePath ( ) ; ctx . fill ( ) ; return brushCanvas ; }
get canvas of a black circle brush used for canvas to draw later
@private
@returns {Object} circle brush canvas
get canvas of a black circle brush used for canvas to draw later