dev@343: /**
dev@343:  * Created by lucast on 23/05/2017.
dev@343:  */
dev@343: 
dev@343: export function interpolatingMapper(hexColours) {
dev@343:   const colours = hexColours.map(n => {
dev@343:     const i = parseInt(n, 16);
dev@343:     return [ ((i >> 16) & 255) / 255.0,
dev@343:       ((i >> 8) & 255) / 255.0,
dev@343:       ((i) & 255) / 255.0 ];
dev@343:   });
dev@343:   const last = colours.length - 1;
dev@343:   return (value => {
dev@343:     const m = value * last;
dev@343:     if (m >= last) {
dev@343:       return colours[last];
dev@343:     }
dev@343:     if (m <= 0) {
dev@343:       return colours[0];
dev@343:     }
dev@343:     const base = Math.floor(m);
dev@343:     const prop0 = base + 1.0 - m;
dev@343:     const prop1 = m - base;
dev@343:     const c0 = colours[base];
dev@343:     const c1 = colours[base + 1];
dev@343:     return [ c0[0] * prop0 + c1[0] * prop1,
dev@343:       c0[1] * prop0 + c1[1] * prop1,
dev@343:       c0[2] * prop0 + c1[2] * prop1 ];
dev@343:   });
dev@343: }
dev@343: 
dev@343: export function iceMapper() {
dev@343:   const hexColours = [
dev@343:     // Based on ColorBrewer ylGnBu
dev@343:     'ffffff', 'ffff00', 'f7fcf0', 'e0f3db', 'ccebc5', 'a8ddb5',
dev@343:     '7bccc4', '4eb3d3', '2b8cbe', '0868ac', '084081', '042040'
dev@343:   ];
dev@343:   hexColours.reverse();
dev@343:   return interpolatingMapper(hexColours);
dev@343: }
dev@343: 
dev@343: export function greenMapper() {
dev@343:   const blue = 0.6666;
dev@343:   const pieslice = 0.3333;
dev@343:   return (value => {
dev@343:     const h = blue - value * 2.0 * pieslice;
dev@343:     const s = 0.5 + value / 2.0;
dev@343:     const v = value;
dev@343:     return this.hsv2rgb(h, s, v);
dev@343:   });
dev@343: }
dev@343: 
dev@343: export function sunsetMapper() {
dev@343:   return (value => {
dev@343:     const r = (value - 0.24) * 2.38;
dev@343:     const g = (value - 0.64) * 2.777;
dev@343:     let b = (3.6 * value);
dev@343:     if (value > 0.277) {
dev@343:       b = 2.0 - b;
dev@343:     }
dev@343:     return [ r, g, b ];
dev@343:   });
dev@343: }
dev@343: 
dev@343: export function hsv2rgb(h, s, v) { // all values in range [0, 1]
dev@343:   const i = Math.floor(h * 6);
dev@343:   const f = h * 6 - i;
dev@343:   const p = v * (1 - s);
dev@343:   const q = v * (1 - f * s);
dev@343:   const t = v * (1 - (1 - f) * s);
dev@343:   let r = 0, g = 0, b = 0;
dev@343:   switch (i % 6) {
dev@343:     case 0: r = v; g = t; b = p; break;
dev@343:     case 1: r = q; g = v; b = p; break;
dev@343:     case 2: r = p; g = v; b = t; break;
dev@343:     case 3: r = p; g = q; b = v; break;
dev@343:     case 4: r = t; g = p; b = v; break;
dev@343:     case 5: r = v; g = p; b = q; break;
dev@343:   }
dev@343:   return [ r, g, b ];
dev@343: }