前端實現頁面水印

前端實現頁面水印的思路,先將名稱畫到canvas上,再將canvas生成base64圖片格式作爲盒子的背景圖追加到頁面上,其中利用pointer-events: none屬性實現點擊穿透.

const watermark = {};
function setWatermark(str) {
    const id = '1.23452384164.123412415';
    if (document.getElementById(id) !== null) {
        document.body.removeChild(document.getElementById(id));
    }
    const can = document.createElement('canvas');
    can.width = 150;
    can.height = 120;
    const cans = can.getContext('2d');
    cans.rotate(-20 * Math.PI / 180);
    cans.font = '20px Vedana';
    cans.fillStyle = 'rgba(200, 200, 200, 0.20)';
    cans.textAlign = 'left';
    cans.textBaseline = 'Middle';
    cans.fillText(str, can.width / 3, can.height / 2);
    const div = document.createElement('div');
    div.id = id;
    // 點擊穿透
    div.style.pointerEvents = 'none';
    div.style.top = '70px';
    div.style.left = '0px';
    div.style.position = 'fixed';
    div.style.zIndex = '2000';
    div.style.width = document.documentElement.clientWidth - 100 + 'px';
    div.style.height = document.documentElement.clientHeight - 100 + 'px';
    div.style.background = 'url(' + can.toDataURL('image/png') + ') left top repeat';
    document.body.appendChild(div);
    return id;
};

// 該方法只允許調用一次
watermark.set = function (str) {
    const id = setWatermark(str);
    setInterval(() => {
        if (document.getElementById(id) === null) {
            id = setWatermark(str);
        }
    }, 500);
    window.onresize = () => {
        setWatermark(str);
    };
};

export default watermark;