js水印功能

直接上代码

export const getmark = () => {
    const setWatermark = (str, doc) => {
        const id = "1.23452164.1234123416";

        if (document.getElementById(id) !== null) {
            if (doc) {
                doc.removeChild(document.getElementById(id));

            } else {
                document.body.removeChild(document.getElementById(id));
            }
        }

        //创建一个画布
        const can = document.createElement("canvas");
        //设置画布的长宽
        can.width = 300;
        can.height = 160;

        const cans = can.getContext("2d");
        //旋转角度
        cans.rotate((-25 * Math.PI) / 180);
        cans.font = "18px Vedana";
        //设置填充绘画的颜色、渐变或者模式
        cans.fillStyle = "rgba(200, 200, 200, 0.49)";
        //设置文本内容的当前对齐方式
        cans.textAlign = "left";
        //设置在绘制文本时使用的当前文本基线
        // cans.textBaseline = "Middle";
        //在画布上绘制填色的文本（输出的文本，开始绘制文本的X坐标位置，开始绘制文本的Y坐标位置）
        cans.fillText(str, can.width / 9, can.height / 2);

        const div = document.createElement("div");
        div.id = id;
        div.style.pointerEvents = "none";
        div.style.top = "30px";
        div.style.left = "0px";
        div.style.position = "fixed";
        div.style.zIndex = "100000";


        div.style.background =
            "url(" + can.toDataURL("image/png") + ") left top repeat";
        if (doc) {
            div.style.width = doc.clientWidth + "px";
            div.style.height = doc.clientHeight + "px";
            div.style.margin=doc.style.margin
            div.style.marginTop=doc.style.marginTop
            div.style.marginLeft=doc.style.marginLeft
            div.style.marginRight=doc.style.marginRight
            div.style.marginBottom=doc.style.marginBottom


            doc.appendChild(div);
        } else {
            div.style.width = document.documentElement.clientWidth + "px";
            div.style.height = document.documentElement.clientHeight + "px";
            document.body.appendChild(div);
        }
        return id;
    };

    // 该方法只允许调用一次
    const watermark = (str, doc) => {
        let id = setWatermark(str, doc);
        setInterval(() => {
            if (document.getElementById(id) === null) {
                id = setWatermark(str, doc);
            }
        }, 500);
        window.onresize = () => {
            setWatermark(str, doc);
        };
    };
    return { watermark };
};

使用：

import { getmark } from '@/utils/watermark.js'
const {watermark}=getmark()