@alttiri/image-hash/src/grayscale.d.ts

Alt-Image-Hash. An alternative image hashing library.

import { GrayImageData } from "./mono-image-data.js";
import { GrayScalingOpt, ImageDataLike } from "./types.js";
/**
 * Using of 1 `getUint32` is faster than 3 accesses by index (`array[N]`).
 *
 * `getCalculateBT601` is faster than:
 *   `array[i / 4] = data[i] * 0.299 + data[i + 1] * 0.587 + data[i + 2] * 0.114;`
 * or `getCalculateAverage` is faster than:
 *   `array[i / 4] = (data[i] + data[i + 1] + data[i + 2]) / 3;`
 *
 * Using `dw.getUint32` inside the function is faster,
 *   than using `dw.getUint32` in a loop and passing `uint` directly to the function.
 *
 * Do not change the get functions' signature.
 */
export declare const getCalculateBT601: typeof getCalculateBT601_Optimized;
/** Note: It's without rounding. It works as with Math.trunc/Math.floor. */
export declare function getCalculateBT601_Original(dw: DataView): (i: number) => number;
/** Faster version of BT601 with very similar results
 * (only 0.05 % difference no more than by 1 in comparison with the rounded version). */
export declare function getCalculateBT601_Optimized(dw: DataView): (i: number) => number;
export declare function getCalculateAverage(dw: DataView): (i: number) => number;
export declare function getCalculateBT709(dw: DataView): (i: number) => number;
/**
 * `getFunc`:
 * - `getCalculateBT601`
 * - `getCalculateAverage`
 * - `getCalculateBT709`
 */
export declare function getGrayData(imageData: ImageDataLike, getFunc?: GrayScalingOpt): GrayImageData;