d3中多个弧的径向渐变 [英] radial gradients for multiple arcs in d3

问题描述

我有以下弧形图:

我想为每个单独的圆弧添加一个渐变，该渐变从每个单独的圆弧的外半径到内半径.

I would like to add a gradient to each of the individual arcs, that flows from the outer radius to the inner radius of each individual arc.

我猜想我需要为每个弧创建一个单独的渐变吗?

I am guessing that I will need to create an individual gradient for each arc?

let radius = 100;

for(let i = 0; i < 5; i ++) {

  let grad = defs.append('radialGradient')
       .attr('id', 'mygrad' + i)
    .attr('gradientUnits', 'userSpaceOnUse')
          .attr('cx', '0')
    .attr('cy', '0')
    .attr('r', radius)

  grad.append('stop')
       .attr('offset', '0%')
    .attr('stop-color', 'white');

  grad.append('stop')
       .attr('offset', '100%')
    .attr('stop-color', 'blue');

  let arc = d3.arc()
    .outerRadius( radius )
    .innerRadius( radius - 50)
    .startAngle( degToRad(-90) )
    .endAngle( degToRad(90) );

  g.append('path')
    .attr('d', arc)
    .attr('fill', `url(#${'mygrad' + i })`)
    .attr('stroke', 'lightgrey');

  radius += 50;
}

let grad = defs.append('radialGradient')
       .attr('id', 'mygrad' + i)
    .attr('r', '80%')

  grad.append('stop')
       .attr('offset', '0%')
    .attr('stop-color', 'white');

grad.append('stop')
   .attr('offset', '100%')
  .attr('stop-color', 'blue');

Codepen

推荐答案

SVG 2添加了 fr 属性.这样就可以为渐变定义内部起始半径.结合在其他定义中引用渐变定义的可能性，您的代码可以重写为

SVG 2 adds a fr attribute. That makes it possible to define an inner start radius for a gradient. In conjunction with the possibility to quote gradient definitions within other definitiions, your code can be rewritten as

let width = 800;
let height = 800;

let svg = d3.select('svg')
    .attr('width', width)
    .attr('height', height);

let defs = svg.append('defs');

let g = svg.append('g')
	  .attr('transform', `translate(${width/2}, ${height/2})`);

let radius = 100;
    
let gradcolors = defs.append('radialGradient')
    .attr('id', 'gradcolors')
    .attr('gradientUnits', 'userSpaceOnUse')
    .attr('cx', '0')
    .attr('cy', '0')

gradcolors.append('stop')
    .attr('offset', '0%')
    .attr('stop-color', 'white');

gradcolors.append('stop')
    .attr('offset', '100%')
    .attr('stop-color', 'blue');

for(let i = 0; i < 5; i++) {

    let grad = defs.append('radialGradient')
        .attr('id', 'mygrad' + i)
        .attr('href', '#gradcolors')
        .attr('fr', radius - 50)
        .attr('r', radius)

    let arc = d3.arc()
        .outerRadius( radius )
        .innerRadius( radius - 50)
        .startAngle( -90 * (Math.PI / 180) )
        .endAngle( 90 * (Math.PI / 180) );

    g.append('path')
        .attr('d', arc)
        .attr('fill', `url(#${'mygrad' + i })`)
        .attr('stroke', 'lightgrey');

    radius += 50;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
<svg> </svg>

或者您使用 spreadMethod ="repeat" 属性可仅定义一个具有无限重复颜色的渐变.

Or you use the spreadMethod="repeat" attribute to define only one gradient with infinitely repeating colors.

let width = 800;
let height = 800;

let svg = d3.select('svg')
    .attr('width', width)
    .attr('height', height);

let defs = svg.append('defs');

let g = svg.append('g')
	  .attr('transform', `translate(${width/2}, ${height/2})`);

let radius = 100;
let radiusWidth = 50;
    
let grad = defs.append('radialGradient')
    .attr('id', 'mygrad')
    .attr('gradientUnits', 'userSpaceOnUse')
    .attr('spreadMethod', 'repeat')
    .attr('cx', '0')
    .attr('cy', '0')
    .attr('r', radiusWidth)

grad.append('stop')
    .attr('offset', '0%')
    .attr('stop-color', 'white');

grad.append('stop')
    .attr('offset', '100%')
    .attr('stop-color', 'blue');

for(let i = 0; i < 5; i++) {

    let arc = d3.arc()
        .outerRadius( radius )
        .innerRadius( radius - 50)
        .startAngle( -90 * (Math.PI / 180) )
        .endAngle( 90 * (Math.PI / 180) );

    g.append('path')
        .attr('d', arc)
        .attr('fill', 'url(#mygrad')
        .attr('stroke', 'lightgrey');

    radius += radiusWidth;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
<svg> </svg>

这篇关于d3中多个弧的径向渐变的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！