@superset-ui/core
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JavaScript
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
import { scaleLinear } from 'd3-scale';
import { interpolateHcl, interpolateNumber, piecewise, quantize, } from 'd3-interpolate';
import ColorScheme from './ColorScheme';
export default class SequentialScheme extends ColorScheme {
isDiverging;
constructor(config) {
super(config);
const { isDiverging = false } = config;
this.isDiverging = isDiverging;
}
/**
* Return a linear scale with a new domain interpolated from the input domain
* to match the number of elements in the color scheme
* because D3 continuous scale uses piecewise mapping between domain and range.
* This is a common use-case when the domain is [min, max]
* and the palette has more than two colors.
*
* @param domain domain of the scale
* @param modifyRange Set this to true if you don't want to modify the domain and
* want to interpolate range to have the same number of elements with domain instead.
*/
createLinearScale(domain = [0, 1], modifyRange = false) {
const scale = scaleLinear().interpolate(interpolateHcl).clamp(true);
return modifyRange || domain.length === this.colors.length
? scale.domain(domain).range(this.getColors(domain.length))
: scale
.domain(quantize(piecewise(interpolateNumber, domain), this.colors.length))
.range(this.colors);
}
/**
* Get colors from this scheme
* @param numColors number of colors to return.
* Will interpolate the current scheme to match the number of colors requested
* @param extent The extent of the color range to use.
* For example [0.2, 1] will rescale the color scheme
* such that color values in the range [0, 0.2) are excluded from the scheme.
*/
getColors(numColors = this.colors.length, extent = [0, 1]) {
if (numColors === this.colors.length &&
extent[0] === 0 &&
extent[1] === 1) {
return this.colors;
}
const piecewiseScale = piecewise(interpolateHcl, this.colors);
const adjustExtent = scaleLinear().range(extent).clamp(true);
return quantize(t => piecewiseScale(adjustExtent(t)), numColors);
}
}
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