image-js/lib/compute/median.js

Image processing and manipulation in JavaScript

// @ts-expect-error: median-quisckselect has no types
import quickMedian from 'median-quickselect';
/**
 * Returns the median pixel of the image. The median is computed on each channel individually.
 * @param image - Image to process.
 * @param options - Median options.
 * @returns Median pixel.
 */
export function median(image, options) {
    const pixel = new Array(image.channels).fill(0);
    if (options) {
        if (options.points.length === 0) {
            throw new RangeError('Array of coordinates is empty.');
        }
        for (let i = 0; i < image.channels; i++) {
            const channel = [];
            for (const point of options.points) {
                if (point.column < 0 ||
                    point.column >= image.width ||
                    point.row < 0 ||
                    point.row >= image.height) {
                    throw new RangeError(`Invalid coordinate: {column: ${point.column}, row: ${point.row}}.`);
                }
                channel.push(image.getValueByPoint(point, i));
            }
            pixel[i] = quickMedian(channel);
        }
    }
    else {
        for (let i = 0; i < image.channels; i++) {
            const channel = image.getChannel(i);
            pixel[i] = quickMedian(channel);
        }
    }
    return pixel;
}
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