HalfFloat

Methods

fromHalf

Convert a half float representation to a number

Argument Type Required Description
input number Yes

toHalf

Convert a number to half float representation

Argument Type Required Description
input number Yes

Source

index.d.ts
/**
* Helper class to convert to/from half float
*/

/**
* Convert a number to half float representation
* @param {number} input
* @return encoded half float number (16 bits)
*/
export function toHalf(input: number): number;

/**
* Convert a half float representation to a number
* @param {number} input
* @return decoded half float number
*/
export function fromHalf(input: number): number;

export declare const HalfFloat: {
toHalf: typeof toHalf;
fromHalf: typeof fromHalf;
}

export default HalfFloat;
index.js
/* eslint-disable no-bitwise */

const floatView = new Float32Array(1);
const int32View = new Int32Array(floatView.buffer);

/* eslint-disable no-bitwise */
/* This method is faster than the OpenEXR implementation (very often
* used, eg. in Ogre), with the additional benefit of rounding, inspired
* by James Tursa?s half-precision code. */
function toHalf(val) {
floatView[0] = val;
const x = int32View[0];

let bits = (x >> 16) & 0x8000; /* Get the sign */
let m = (x >> 12) & 0x07ff; /* Keep one extra bit for rounding */
const e = (x >> 23) & 0xff; /* Using int is faster here */

/* If zero, or denormal, or exponent underflows too much for a denormal
* half, return signed zero. */
if (e < 103) {
return bits;
}

/* If NaN, return NaN. If Inf or exponent overflow, return Inf. */
if (e > 142) {
bits |= 0x7c00;
/* If exponent was 0xff and one mantissa bit was set, it means NaN,
* not Inf, so make sure we set one mantissa bit too. */
bits |= (e === 255 ? 0 : 1) && x & 0x007fffff;
return bits;
}

/* If exponent underflows but not too much, return a denormal */
if (e < 113) {
m |= 0x0800;
/* Extra rounding may overflow and set mantissa to 0 and exponent
* to 1, which is OK. */
bits |= (m >> (114 - e)) + ((m >> (113 - e)) & 1);
return bits;
}

bits |= ((e - 112) << 10) | (m >> 1);
/* Extra rounding. An overflow will set mantissa to 0 and increment
* the exponent, which is OK. */
bits += m & 1;
return bits;
}

function fromHalf(h) {
const s = (h & 0x8000) >> 15;
const e = (h & 0x7c00) >> 10;
const f = h & 0x03ff;

if (e === 0) {
return (s ? -1 : 1) * 2 ** -14 * (f / 2 ** 10);
}

if (e === 0x1f) {
return f ? NaN : (s ? -1 : 1) * Infinity;
}

return (s ? -1 : 1) * 2 ** (e - 15) * (1 + f / 2 ** 10);
}

export default {
fromHalf,
toHalf,
};