Accueil / npm / three@0.186.1 / examples / jsm / math / Lut.js
Lut.js
import {
Color,
LinearSRGBColorSpace,
MathUtils
} from 'three';
/**
* Represents a lookup table for colormaps. It is used to determine the color
* values from a range of data values.
*
* ```js
* const lut = new Lut( 'rainbow', 512 );
* const color = lut.getColor( 0.5 );
* ```
*
* @three_import import { Lut } from 'three/addons/math/Lut.js';
*/
class Lut {
/**
* Constructs a new Lut.
*
* @param {('rainbow'|'cooltowarm'|'blackbody'|'grayscale')} [colormap='rainbow'] - Sets a colormap from predefined list of colormaps.
* @param {number} [count=32] - Sets the number of colors used to represent the data array.
*/
constructor( colormap, count = 32 ) {
/**
* This flag can be used for type testing.
*
* @type {boolean}
* @readonly
* @default true
*/
this.isLut = true;
/**
* The lookup table for the selected color map
*
* @type {Array<Color>}
*/
this.lut = [];
/**
* The currently selected color map.
*
* @type {Array<Array<number>>}
*/
this.map = [];
/**
* The number of colors of the current selected color map.
*
* @type {number}
* @default 32
*/
this.n = 0;
/**
* The minimum value to be represented with the lookup table.
*
* @type {number}
* @default 0
*/
this.minV = 0;
/**
* The maximum value to be represented with the lookup table.
*
* @type {number}
* @default 1
*/
this.maxV = 1;
this.setColorMap( colormap, count );
}
/**
* Sets the given LUT.
*
* @param {Lut} value - The LUT to set.
* @return {Lut} A reference to this LUT.
*/
set( value ) {
if ( value.isLut === true ) {
this.copy( value );
}
return this;
}
/**
* Sets the minimum value to be represented with this LUT.
*
* @param {number} min - The minimum value to be represented with the lookup table.
* @return {Lut} A reference to this LUT.
*/
setMin( min ) {
this.minV = min;
return this;
}
/**
* Sets the maximum value to be represented with this LUT.
*
* @param {number} max - The maximum value to be represented with the lookup table.
* @return {Lut} A reference to this LUT.
*/
setMax( max ) {
this.maxV = max;
return this;
}
/**
* Configure the lookup table for the given color map and number of colors.
*
* @param {string} colormap - The name of the color map.
* @param {number} [count=32] - The number of colors.
* @return {Lut} A reference to this LUT.
*/
setColorMap( colormap, count = 32 ) {
this.map = ColorMapKeywords[ colormap ] || ColorMapKeywords.rainbow;
this.n = count;
const step = 1.0 / this.n;
const minColor = new Color();
const maxColor = new Color();
this.lut.length = 0;
// sample at 0
this.lut.push( new Color( this.map[ 0 ][ 1 ] ) );
// sample at 1/n, ..., (n-1)/n
for ( let i = 1; i < count; i ++ ) {
const alpha = i * step;
for ( let j = 0; j < this.map.length - 1; j ++ ) {
if ( alpha > this.map[ j ][ 0 ] && alpha <= this.map[ j + 1 ][ 0 ] ) {
const min = this.map[ j ][ 0 ];
const max = this.map[ j + 1 ][ 0 ];
minColor.setHex( this.map[ j ][ 1 ], LinearSRGBColorSpace );
maxColor.setHex( this.map[ j + 1 ][ 1 ], LinearSRGBColorSpace );
const color = new Color().lerpColors( minColor, maxColor, ( alpha - min ) / ( max - min ) );
this.lut.push( color );
}
}
}
// sample at 1
this.lut.push( new Color( this.map[ this.map.length - 1 ][ 1 ] ) );
return this;
}
/**
* Copies the given lut.
*
* @param {Lut} lut - The LUT to copy.
* @return {Lut} A reference to this LUT.
*/
copy( lut ) {
this.lut = lut.lut;
this.map = lut.map;
this.n = lut.n;
this.minV = lut.minV;
this.maxV = lut.maxV;
return this;
}
/**
* Returns an instance of Color for the given data value.
*
* @param {number} alpha - The value to lookup.
* @return {Color} The color from the LUT.
*/
getColor( alpha ) {
alpha = MathUtils.clamp( alpha, this.minV, this.maxV );
alpha = ( alpha - this.minV ) / ( this.maxV - this.minV );
const colorPosition = Math.round( alpha * this.n );
return this.lut[ colorPosition ];
}
/**
* Adds a color map to this Lut instance.
*
* @param {string} name - The name of the color map.
* @param {Array<Array<number>>} arrayOfColors - An array of color values. Each value is an array
* holding a threshold and the actual color value as a hexadecimal number.
* @return {Lut} A reference to this LUT.
*/
addColorMap( name, arrayOfColors ) {
ColorMapKeywords[ name ] = arrayOfColors;
return this;
}
/**
* Creates a canvas in order to visualize the lookup table as a texture.
*
* @return {HTMLCanvasElement} The created canvas.
*/
createCanvas() {
const canvas = document.createElement( 'canvas' );
canvas.width = 1;
canvas.height = this.n;
this.updateCanvas( canvas );
return canvas;
}
/**
* Updates the given canvas with the Lut's data.
*
* @param {HTMLCanvasElement} canvas - The canvas to update.
* @return {HTMLCanvasElement} The updated canvas.
*/
updateCanvas( canvas ) {
const ctx = canvas.getContext( '2d', { alpha: false } );
const imageData = ctx.getImageData( 0, 0, 1, this.n );
const data = imageData.data;
let k = 0;
const step = 1.0 / this.n;
const minColor = new Color();
const maxColor = new Color();
const finalColor = new Color();
for ( let i = 1; i >= 0; i -= step ) {
for ( let j = this.map.length - 1; j >= 0; j -- ) {
if ( i < this.map[ j ][ 0 ] && i >= this.map[ j - 1 ][ 0 ] ) {
const min = this.map[ j - 1 ][ 0 ];
const max = this.map[ j ][ 0 ];
minColor.setHex( this.map[ j - 1 ][ 1 ], LinearSRGBColorSpace );
maxColor.setHex( this.map[ j ][ 1 ], LinearSRGBColorSpace );
finalColor.lerpColors( minColor, maxColor, ( i - min ) / ( max - min ) );
data[ k * 4 ] = Math.round( finalColor.r * 255 );
data[ k * 4 + 1 ] = Math.round( finalColor.g * 255 );
data[ k * 4 + 2 ] = Math.round( finalColor.b * 255 );
data[ k * 4 + 3 ] = 255;
k += 1;
}
}
}
ctx.putImageData( imageData, 0, 0 );
return canvas;
}
}
const ColorMapKeywords = {
'rainbow': [[ 0.0, 0x0000FF ], [ 0.2, 0x00FFFF ], [ 0.5, 0x00FF00 ], [ 0.8, 0xFFFF00 ], [ 1.0, 0xFF0000 ]],
'cooltowarm': [[ 0.0, 0x3C4EC2 ], [ 0.2, 0x9BBCFF ], [ 0.5, 0xDCDCDC ], [ 0.8, 0xF6A385 ], [ 1.0, 0xB40426 ]],
'blackbody': [[ 0.0, 0x000000 ], [ 0.2, 0x780000 ], [ 0.5, 0xE63200 ], [ 0.8, 0xFFFF00 ], [ 1.0, 0xFFFFFF ]],
'grayscale': [[ 0.0, 0x000000 ], [ 0.2, 0x404040 ], [ 0.5, 0x7F7F80 ], [ 0.8, 0xBFBFBF ], [ 1.0, 0xFFFFFF ]]
};
export { Lut, ColorMapKeywords };