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colorspace.ts
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colorspace.ts
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import { Accessor, Document, Primitive, Transform, vec3 } from '@gltf-transform/core';
const NAME = 'colorspace';
/** Options for the {@link colorspace} function. */
export interface ColorspaceOptions {
/** Must be `"sRGB"`. Required. */
inputEncoding: string;
}
/**
* Vertex color colorspace correction. The glTF format requires vertex colors to be stored
* as linear values, and this function provides a way to correct vertex colors that are
* (incorrectly) sRGB.
*/
export function colorspace (options: ColorspaceOptions): Transform {
return (doc: Document): void => {
const logger = doc.getLogger();
if (options.inputEncoding === 'linear') {
logger.info(`${NAME}: Vertex colors already linear. Skipping conversion.`);
return;
}
if (options.inputEncoding !== 'sRGB') {
logger.error(
`${NAME}: Unknown input encoding "${options.inputEncoding}" – should be "sRGB" or `
+ '"linear". Skipping conversion.'
);
return;
}
const converted = new Set<Accessor>();
// Source: THREE.Color
function sRGBToLinear( c: number ): number {
return ( c < 0.04045 )
? c * 0.0773993808
: Math.pow( c * 0.9478672986 + 0.0521327014, 2.4 );
}
function updatePrimitive(primitive: Primitive): void {
const color = [0, 0, 0] as vec3;
let attribute: Accessor | null;
for (let i = 0; (attribute = primitive.getAttribute(`COLOR_${i}`)); i++) {
if (converted.has(attribute)) continue;
for (let j = 0; j < attribute.getCount(); j++) {
attribute.getElement(j, color);
color[0] = sRGBToLinear(color[0]);
color[1] = sRGBToLinear(color[1]);
color[2] = sRGBToLinear(color[2]);
attribute.setElement(j, color);
}
converted.add(attribute);
}
}
doc.getRoot()
.listMeshes()
.forEach((mesh) => mesh.listPrimitives().forEach(updatePrimitive));
logger.debug(`${NAME}: Complete.`);
};
}