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Add support for ICtCp color space (#216)
* Use power of two as a step for ranges approximator * Add support for ITP (ICtCp) color space
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‎docs/api.md

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@@ -1547,6 +1547,7 @@ Mode | Color space | Definition object
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`hsl` | HSL color space | `modeHsl`
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`hsv` | HSV color space | `modeHsv`
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`hwb` | HWB color space | `modeHwb`
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`itp` | IC<sub>t</sub>C<sub>p</sub> color space | `modeItp`
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`jab` | J<sub>z</sub>a<sub>z</sub>b<sub>z</sub> color space | `modeJab`
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`jch` | J<sub>z</sub>a<sub>z</sub>b<sub>z</sub> in cylindrical form | `modeJch`
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`lab` | CIELAB color space (D50 Illuminant) | `modeLab`

‎docs/color-spaces.md

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@@ -438,7 +438,21 @@ It has the default _Chroma from Luma_ adjustment applied (effectively Y is subtr
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| ------- | ------------- | ----------- |
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| `x` | `[-0.0154, 0.0281]`≈ | Cyan-red component |
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| `y` | `[0, 0.8453]`≈ | Luma |
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| `b` | `[ -0.2778, 0.3880 ]` ≈ | Blue-yellow component |
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| `b` | `[ -0.2778, 0.3880 ]`≈ | Blue-yellow component |
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Does not have gamut limits.
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#### `itp`
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IC<sub>t</sub>C<sub>p</sub> (or ITP) color space, as defined in ITU-R Recommendation BT.2100.
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| Channel | Range | Description |
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|---------|-------------------|-----------------------|
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| `i` | `[0, 0.581]`≈ | Intensity |
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| `t` | `[-0.282, 0.278]`≈ | Blue-yellow component |
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| `p` | `[-0.162, 0.279]`≈ | Green–red component |
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Serialized as `color(--ictcp i t p)`, with the `none` keyword for any missing color channel. An explicit `alpha < 1` is included as ` / alpha`.
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Does not have gamut limits.
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‎docs/guides/tree-shaking.md

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@@ -125,7 +125,7 @@ interpolate(['red', 'green'], 'lch');
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Bootstrap all the color spaces available in Culori.
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It provides the following named exports: `a98`, `cubehelix`, `dlab`, `dlch`, `hsi`, `hsl`, `hsv`, `hwb`, `jab`, `jch`, `lab`, `lab65`, `lch`, `lch65`, `lchuv`, `lrgb`, `luv`, `okhsl`, `okhsv`, `oklab`, `oklch`, `p3`, `prophoto`, `rec2020`, `rgb`, `xyb`, `xyz50`, `xyz65`, and `yiq`.
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It provides the following named exports: `a98`, `cubehelix`, `dlab`, `dlch`, `hsi`, `hsl`, `hsv`, `hwb`, `itp`, `jab`, `jch`, `lab`, `lab65`, `lch`, `lch65`, `lchuv`, `lrgb`, `luv`, `okhsl`, `okhsv`, `oklab`, `oklch`, `p3`, `prophoto`, `rec2020`, `rgb`, `xyb`, `xyz50`, `xyz65`, and `yiq`.
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```js
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import 'culori/all';

‎src/bootstrap/all.js

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@@ -7,6 +7,7 @@ import modeHsi from '../hsi/definition.js';
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import modeHsl from '../hsl/definition.js';
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import modeHsv from '../hsv/definition.js';
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import modeHwb from '../hwb/definition.js';
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import modeItp from '../itp/definition.js';
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import modeJab from '../jab/definition.js';
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import modeJch from '../jch/definition.js';
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import modeLab from '../lab/definition.js';
@@ -38,6 +39,7 @@ export const hsi = useMode(modeHsi);
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export const hsl = useMode(modeHsl);
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export const hsv = useMode(modeHsv);
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export const hwb = useMode(modeHwb);
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export const itp = useMode(modeItp);
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export const jab = useMode(modeJab);
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export const jch = useMode(modeJch);
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export const lab = useMode(modeLab);

‎src/index-fn.js

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@@ -7,6 +7,7 @@ export { default as modeHsi } from './hsi/definition.js';
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export { default as modeHsl } from './hsl/definition.js';
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export { default as modeHsv } from './hsv/definition.js';
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export { default as modeHwb } from './hwb/definition.js';
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export { default as modeItp } from './itp/definition.js';
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export { default as modeJab } from './jab/definition.js';
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export { default as modeJch } from './jch/definition.js';
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export { default as modeLab } from './lab/definition.js';
@@ -171,6 +172,7 @@ export { default as convertHsiToRgb } from './hsi/convertHsiToRgb.js';
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export { default as convertHslToRgb } from './hsl/convertHslToRgb.js';
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export { default as convertHsvToRgb } from './hsv/convertHsvToRgb.js';
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export { default as convertHwbToRgb } from './hwb/convertHwbToRgb.js';
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export { default as convertItpToXyz65 } from './itp/convertItpToXyz65.js';
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export { default as convertJabToJch } from './jch/convertJabToJch.js';
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export { default as convertJabToRgb } from './jab/convertJabToRgb.js';
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export { default as convertJabToXyz65 } from './jab/convertJabToXyz65.js';
@@ -212,6 +214,7 @@ export { default as convertRgbToYiq } from './yiq/convertRgbToYiq.js';
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export { default as convertRgbToXyb } from './xyb/convertRgbToXyb.js';
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export { default as convertXybToRgb } from './xyb/convertXybToRgb.js';
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export { default as convertXyz65ToA98 } from './a98/convertXyz65ToA98.js';
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export { default as convertXyz65ToItp } from './itp/convertXyz65ToItp.js';
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export { default as convertXyz65ToJab } from './jab/convertXyz65ToJab.js';
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export { default as convertXyz65ToLab65 } from './lab65/convertXyz65ToLab65.js';
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export { default as convertXyz65ToP3 } from './p3/convertXyz65ToP3.js';

‎src/index.js

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@@ -7,6 +7,7 @@ import modeHsi from './hsi/definition.js';
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import modeHsl from './hsl/definition.js';
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import modeHsv from './hsv/definition.js';
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import modeHwb from './hwb/definition.js';
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import modeItp from './itp/definition.js';
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import modeJab from './jab/definition.js';
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import modeJch from './jch/definition.js';
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import modeLab from './lab/definition.js';
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export { default as convertHslToRgb } from './hsl/convertHslToRgb.js';
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export { default as convertHsvToRgb } from './hsv/convertHsvToRgb.js';
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export { default as convertHwbToRgb } from './hwb/convertHwbToRgb.js';
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export { default as convertItpToXyz65 } from './itp/convertItpToXyz65.js';
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export { default as convertJabToJch } from './jch/convertJabToJch.js';
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export { default as convertJabToRgb } from './jab/convertJabToRgb.js';
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export { default as convertJabToXyz65 } from './jab/convertJabToXyz65.js';
@@ -218,6 +220,7 @@ export { default as convertXyz50ToProphoto } from './prophoto/convertXyz50ToProp
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export { default as convertXyz50ToRgb } from './xyz50/convertXyz50ToRgb.js';
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export { default as convertXyz50ToXyz65 } from './xyz65/convertXyz50ToXyz65.js';
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export { default as convertXyz65ToA98 } from './a98/convertXyz65ToA98.js';
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export { default as convertXyz65ToItp } from './itp/convertXyz65ToItp.js';
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export { default as convertXyz65ToJab } from './jab/convertXyz65ToJab.js';
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export { default as convertXyz65ToLab65 } from './lab65/convertXyz65ToLab65.js';
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export { default as convertXyz65ToP3 } from './p3/convertXyz65ToP3.js';
@@ -235,6 +238,7 @@ export {
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modeHsl,
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modeHsv,
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modeHwb,
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modeItp,
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modeJab,
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modeJch,
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modeLab,
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export const hsl = useMode(modeHsl);
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export const hsv = useMode(modeHsv);
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export const hwb = useMode(modeHwb);
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export const itp = useMode(modeItp);
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export const jab = useMode(modeJab);
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export const jch = useMode(modeJch);
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export const lab = useMode(modeLab);

‎src/itp/constants.js

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// PQ Constants
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// https://en.wikipedia.org/wiki/High-dynamic-range_video#Perceptual_quantizer
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export const M1 = 2610 / 16384;
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export const M2 = 2523 / 32;
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export const IM1 = 16384 / 2610;
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export const IM2 = 32 / 2523;
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export const C1 = 3424 / 4096;
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export const C2 = 2413 / 128;
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export const C3 = 2392 / 128;
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// Maximum luminance in PQ is 10,000 cd/m^2
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// Relative XYZ has Y=1 for media white
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// BT.2048 says media white Y=203 at PQ 58
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//
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// This is confirmed here: https://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-BT.2408-3-2019-PDF-E.pdf
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export const YW = 203;

‎src/itp/convertItpToXyz65.js

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import { YW } from './constants.js';
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import { transferPqDecode } from '../hdr/transfer.js';
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const convertItpToXyz65 = ({ i, t, p, alpha }) => {
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const [l, m, s] = [
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i + 0.008609037037932761 * t + 0.11102962500302593 * p,
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i - 0.00860903703793275 * t - 0.11102962500302599 * p,
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i + 0.5600313357106791 * t - 0.32062717498731885 * p
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].map(transferPqDecode);
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const [x, y, z] = [
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2.0701522183894219 * l -
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1.3263473389671556 * m +
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0.2066510476294051 * s,
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0.3647385209748074 * l + 0.680566024947227 * m - 0.0453045459220346 * s,
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-0.049747207535812 * l - 0.0492609666966138 * m + 1.1880659249923042 * s
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].map(c => Math.max(c / YW, 0));
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const res = { mode: 'xyz65', x, y, z };
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if (alpha !== undefined) {
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res.alpha = alpha;
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}
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return res;
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};
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export default convertItpToXyz65;

‎src/itp/convertXyz65ToItp.js

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import { YW } from './constants.js';
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import { transferPqEncode } from '../hdr/transfer.js';
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const convertXyz65ToItp = ({ x, y, z, alpha }) => {
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const [absX, absY, absZ] = [x, y, z].map(c => Math.max(c * YW, 0));
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const [l, m, s] = [
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0.3592832590121217 * absX +
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0.6976051147779502 * absY -
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0.0358915932320289 * absZ,
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-0.1920808463704995 * absX +
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1.1004767970374323 * absY +
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0.0753748658519118 * absZ,
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0.0070797844607477 * absX +
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0.0748396662186366 * absY +
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0.8433265453898765 * absZ
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].map(transferPqEncode);
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const i = 0.5 * l + 0.5 * m;
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const t = 1.61376953125 * l + -3.323486328125 * m + 1.709716796875 * s;
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const p = 4.378173828125 * l + -4.24560546875 * m + -0.132568359375 * s;
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const res = { mode: 'itp', i, t, p };
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if (alpha !== undefined) {
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res.alpha = alpha;
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}
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return res;
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};
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export default convertXyz65ToItp;

‎src/itp/definition.js

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import { interpolatorLinear } from '../interpolate/linear.js';
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import { fixupAlpha } from '../fixup/alpha.js';
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import convertItpToXyz65 from './convertItpToXyz65.js';
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import convertXyz65ToItp from './convertXyz65ToItp.js';
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import { convertRgbToXyz65, convertXyz65ToRgb } from '../index.js';
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/*
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ICtCp (or ITP) color space, as defined in ITU-R Recommendation BT.2100.
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ICtCp is drafted to be supported in CSS within
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[CSS Color HDR Module Level 1](https://drafts.csswg.org/css-color-hdr/#ICtCp) spec.
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*/
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const definition = {
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mode: 'itp',
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channels: ['i', 't', 'p', 'alpha'],
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parse: ['--ictcp'],
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serialize: '--ictcp',
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toMode: {
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xyz65: convertItpToXyz65,
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rgb: color => convertXyz65ToRgb(convertItpToXyz65(color))
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},
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fromMode: {
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xyz65: convertXyz65ToItp,
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rgb: color => convertXyz65ToItp(convertRgbToXyz65(color))
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},
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ranges: {
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i: [0, 0.581],
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t: [-0.369, 0.272],
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p: [-0.164, 0.331]
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},
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interpolate: {
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i: interpolatorLinear,
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t: interpolatorLinear,
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p: interpolatorLinear,
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alpha: { use: interpolatorLinear, fixup: fixupAlpha }
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}
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};
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export default definition;

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