               canvasBox.appendChild(backCanvasForDebug);

                {
                    // start
                    const colorGray = colorArr => {
                        const grayArr = [];
                        for (let i = 0; i < colorArr.length; i += 4) {
                            // 灰度计算 参考 https://blog.csdn.net/xdrt81y/article/details/8289963
                            const gray = (colorArr[i] * 19595 + colorArr[i + 1] * 38469 + colorArr[i + 2] * 7472) >> 16;
             