image-js/lib/filters/medianFilter.js

Image processing and manipulation in JavaScript

import { xMedian } from 'ml-spectra-processing';
import { Image } from '../Image.js';
import { getDefaultColor } from "../utils/getDefaultColor.js";
import { getBorderInterpolation } from '../utils/interpolateBorder.js';
import checkProcessable from '../utils/validators/checkProcessable.js';
/**
 * Calculate a new image that replaces all pixel values by the median of neighbouring pixels.
 * @param image - Image to be filtered.
 * @param options - MedianFilterOptions
 * @returns Image after median filter.
 */
export function medianFilter(image, options = {}) {
    const { cellSize = 3, borderType = 'reflect101', borderValue = getDefaultColor(image), } = options;
    checkProcessable(image, {
        bitDepth: [8, 16],
    });
    if (cellSize < 1) {
        throw new RangeError(`Invalid property "cellSize". Must be greater than 0. Received ${cellSize}.`);
    }
    if (cellSize % 2 === 0) {
        throw new RangeError(`Invalid property "cellSize". Must be an odd number. Received ${cellSize}.`);
    }
    const interpolateBorder = getBorderInterpolation(borderType, borderValue);
    const newImage = Image.createFrom(image);
    const size = cellSize ** 2;
    const cellValues = new Uint16Array(size);
    const halfCellSize = (cellSize - 1) / 2;
    for (let channel = 0; channel < image.channels; channel++) {
        for (let row = 0; row < image.height; row++) {
            for (let column = 0; column < image.width; column++) {
                let n = 0;
                for (let cellRow = -halfCellSize; cellRow <= halfCellSize; cellRow++) {
                    for (let cellColumn = -halfCellSize; cellColumn <= halfCellSize; cellColumn++) {
                        cellValues[n++] = interpolateBorder(column + cellColumn, row + cellRow, channel, image);
                    }
                }
                newImage.setValue(column, row, channel, xMedian(cellValues));
            }
        }
    }
    return newImage;
}
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