A function to map rgba value into better accessible pixels

pixelmapper.js

/*
 * A function to map rgba value into better accessible pixels 
 * */

// ========= Actual Pixels ( 2x2 image ) ========== 
/* 
    let x = [
        [1, 2],
        [3, 4]
    ]
*/

// =============== We Get a OneDimensional Array ===============
// let z = ['1r', '1g', '1b', '1a', '2r', '2g', '2b', '2a', '3r', '3g', '3b', '3a', '4r', '4g', '4b', '4a']

// ================ We want ===================
/*
    let y = [
        [ ['1r', '1g', '1b', '1a'], ['2r', '2g', '2b', '2a'] ],
        [ ['3r', '3g', '3b', '3a'], ['4r', '4g', '4b', '4a'] ]
]
*/

function pixelMaper(img_data, height, width) {
    let pixels = [];

    let width_step = width * 4;
    for (let i = 0; i < img_data.length; i += width_step) {
        let row = img_data.slice(i, i + width_step);
        let newRow = [];
        for (let j = 0; j < row.length; j += 4) {
            let pixel = row.slice(j, j + 4);
            newRow.push(pixel);
        }
        pixels.push(newRow);
    }
    return pixels;
}