blog/public/plugin/c3-0.7.20/src/color.ts

import { ChartInternal } from './core'
import { notEmpty } from './util'

ChartInternal.prototype.generateColor = function() {
  var $$ = this,
    config = $$.config,
    d3 = $$.d3,
    colors = config.data_colors,
    pattern = notEmpty(config.color_pattern)
      ? config.color_pattern
      : d3.schemeCategory10,
    callback = config.data_color,
    ids = []

  return function(d) {
    var id = d.id || (d.data && d.data.id) || d,
      color

    // if callback function is provided
    if (colors[id] instanceof Function) {
      color = colors[id](d)
    }
    // if specified, choose that color
    else if (colors[id]) {
      color = colors[id]
    }
    // if not specified, choose from pattern
    else {
      if (ids.indexOf(id) < 0) {
        ids.push(id)
      }
      color = pattern[ids.indexOf(id) % pattern.length]
      colors[id] = color
    }
    return callback instanceof Function ? callback(color, d) : color
  }
}
ChartInternal.prototype.generateLevelColor = function() {
  var $$ = this,
    config = $$.config,
    colors = config.color_pattern,
    threshold = config.color_threshold,
    asValue = threshold.unit === 'value',
    values =
      threshold.values && threshold.values.length ? threshold.values : [],
    max = threshold.max || 100
  return notEmpty(threshold) && notEmpty(colors)
    ? function(value) {
        var i,
          v,
          color = colors[colors.length - 1]
        for (i = 0; i < values.length; i++) {
          v = asValue ? value : (value * 100) / max
          if (v < values[i]) {
            color = colors[i]
            break
          }
        }
        return color
      }
    : null
}