leonitousconforti/tinyburg

import type { Image } from "./image.js";

import assert from "node:assert";
import { sourceImageGuard } from "../parameter-guards/source-image-guard.js";
import { uint8safeIntegerGuard } from "../parameter-guards/uint8-safe-integer.js";

/**
 * Thresholds an image based on a threshold value. Any pixel above the threshold
 * is set to 255 and anything below the threshold is set to 0. The thresholded
 * image will have the same width, height, and number of channels as the source
 * image.
 *
 * @param sourceImage - The image to threshold
 * @param threshold - The threshold value
 */
export const thresholdImage = (sourceImage: Image, threshold: number): Image => {
    sourceImageGuard(sourceImage);
    uint8safeIntegerGuard(threshold);
    assert(sourceImage.channels === 1);

    const { width, height, channels, format, pixels } = sourceImage;
    const thresholdImage: Image = {
        width,
        height,
        format,
        channels,
        pixels: Buffer.alloc(width * height * channels),
    };

    for (let pixelIndex = 0; pixelIndex < width * height * channels; pixelIndex++) {
        thresholdImage.pixels[pixelIndex] = pixels[pixelIndex] >= threshold ? 255 : 0;
    }
    return thresholdImage;
};