Method constructor

pixelizer.js:1228–1232

(pixels, level = 0)

// ColorBox类（从main.js复制）
class ColorBox {
    constructor(pixels, level = 0) {
        this.pixels = pixels;
        this.level = level;
        this.computeMinMax();
    }

    computeMinMax() {
        let minR = 255, minG = 255, minB = 255, minA = 255;