getColorAmount.js

const getPixels = require("get-pixels");

//1px only black https://i.imgur.com/dStJ1Og.png
//2px only black https://i.imgur.com/5z46WVp.png
//88x62px only black https://i.imgur.com/ZtGMUh9.png
//88x62px black and red https://i.imgur.com/67IZCaD.png
//220x297px black and red https://i.imgur.com/KTNnJGF.jpg
function check(uintArr) {
    let r = uintArr[0], g = uintArr[1], b = uintArr[2], a = uintArr[3];
    for (let i = 0, l = uintArr.length; i < l; i += 4) {
        if (
            r !== uintArr[i] ||
            g !== uintArr[i+1] ||
            b !== uintArr[i+2] ||
            a !== uintArr[i+3]
        ) {
            return false;
        }
    }
    return true;
}

getPixels("https://i.imgur.com/JiHtQuR.jpg", function(err, ndarray) {
    if(err) {
        console.log("Bad image path!");
        return;
    }

    const uintArr = new Uint8Array(ndarray.data);
    console.log('Is image one color? ', check(uintArr));
});