@thi.ng/tensors/histogram.d.ts

0D/1D/2D/3D/4D tensors with extensible polymorphic operations and customizable storage

import type { Range1_24 } from "@thi.ng/api";
import type { ITensor, ITensor1 } from "./api.js";
/**
 * Computes the histogram of given uint-based tensor. Returns histogram as a 1D
 * tensor of `u32` values. The `depth` param defines the value range (as number
 * of bits) of the input values (max. 24 bits). The optional `mask` and `shift`
 * params are used to transform input values like so: `(x >>> shift) & mask`.
 * This allows extracting sub-ranges from a packed integer representation (e.g.
 * indidivual color channels from a pixel buffer).
 *
 * @remarks
 * Also see {@link equalizeHistogram} and {@link applyLUT}.
 *
 * @example
 * ```ts tangle:../export/histogram-uint.ts
 * import { histogramUint, tensor } from "@thi.ng/tensors";
 *
 * const src = tensor("u8", [3,3], { data: [12,4,4, 16,16,32, 64,48,4] });
 *
 * // compute histogram with input value range = 8 bits
 * const hist = histogramUint(src, 8);
 *
 * console.log(hist.data);
 * // Uint8Array(256) [
 * //   0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0,
 * //   2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 * //   1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 * //   1, 0, 0, 0, 0, 0, 0 ...
 * // ]
 * ```
 *
 * @param src
 * @param depth
 * @param mask
 * @param shift
 */
export declare const histogramUint: (src: ITensor, depth: Range1_24, mask?: number, shift?: number) => ITensor1<number>;
/**
 * Takes a 1D tensor containing a histogram (e.g. obtained via
 * {@link histogramUint}) and applies histogram equalization by first
 * normalizing the histogram, computing its cumulative distribution (via
 * {@link cdf}), determining the used min/max input value range and then
 * rescaling values to produce a lookup table (LUT) for remapping input values
 * via {@link applyLUT}.
 *
 * @remarks
 * References:
 *
 * - https://en.wikipedia.org/wiki/Histogram_equalization
 *
 * @param out
 * @param src
 * @param depth
 * @param numSamples
 * @param threshold
 */
export declare const equalizeHistogram: (out: ITensor1 | null, src: ITensor1, depth: number, numSamples: number, threshold?: number) => ITensor1;
/**
 * Applies given lookup table to `a` and writes results to `out`. I.e. `out[i] =
 * lut[a[i]]`. This is intended as last step of a histogram equalization process
 * to transform `a` via applying the histogram obtained via
 * {@link equalizeHistogram}.
 *
 * @param out
 * @param a
 * @param lut
 */
export declare const applyLUT: (out: ITensor | null, a: ITensor, lut: ITensor1) => import("./api.js").ITensor0<number>;
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