javascript - Chart.js 阴影区域

Question

Chart.js ( http://www.chartjs.org/docs/ ) 可以使用“fillColor”属性填充折线图下方的颜色(填充折线图本身和 x 轴之间的区域)。

我想知道的是 Chart.js 是否可以配置为创建阴影区域，如下所示:

http://peltiertech.com/Excel/pix5/HorizBands09.png

谢谢。

Answer 1

折线图的阴影区域

您可以扩展图表来执行此操作。

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预览

或

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脚本

Chart.types.Line.extend({
    name: "LineAlt",
    initialize: function (data) {
        Chart.types.Line.prototype.initialize.apply(this, arguments);

        var ranges = [
            {
                start: 100,
                end: 75,
                color: 'rgba(250,0,0,0.5)'
            },
            {
                start: 75,
                end: 50,
                color: 'rgba(0,250,0,0.5)'
            },
            {
                start: 50,
                end: 25,
                color: 'rgba(0,0,250,0.5)'
            },
            {
                start: 25,
                end: 0,
                color: 'rgba(250,250,0,0.5)'
            }
        ];

        var scale = this.scale;
        var rangesStart = scale.calculateY(ranges[0].start);
        var rangesEnd = scale.calculateY(ranges[ranges.length - 1].end);
        var gradient = this.chart.ctx.createLinearGradient(0, rangesStart, 0, rangesEnd);

        ranges.forEach(function (range) {
            gradient.addColorStop((scale.calculateY(range.start) - rangesStart) / (rangesEnd - rangesStart), range.color);
            gradient.addColorStop((scale.calculateY(range.end) - rangesStart) / (rangesEnd - rangesStart), range.color);
        })

        this.datasets[0].fillColor = gradient;
    }
});

然后

...
new Chart(ctx).LineAlt(data);

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如果你想遮蔽整个背景使用

var originalDraw = scale.draw;
scale.draw = function() {
    originalDraw.apply(this, arguments);

  ctx.save();
  ctx.fillStyle = gradient;
  ctx.fillRect(scale.calculateX(0), scale.startPoint, scale.width, scale.endPoint - scale.startPoint);
  ctx.restore();
}

代替 this.datasets[0].fillColor = gradient;

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fiddle (线下)- http://jsfiddle.net/61vg048r/

fiddle (整个背景)- http://jsfiddle.net/u4Lk7xns/