How to set watermark stack in Javascript

How to set watermark stack in Javascript: 1. Create page element p through javascript, and create a text node in the p element to display the watermark content; 2. Set the style of p element and set its zIndex to a higher value value and set the transparency to achieve a watermark effect floating on the page.

The operating environment of this article: windows7 system, javascript version 1.8.5, Dell G3 computer.

How to set watermark stack in Javascript?

Watermarks are all over the place: html javascript implements dynamic page watermarks

1. Basic principles

• After the page is loaded , create the page element p through javascript, and create a text node in the p element to display the watermark content

• Set the p element style, set its zIndex to a higher value, and set the transparency , to achieve the watermark effect floating on the page

The core logic is as follows

var mask_p = document.createElement('p');
    mask_p.id = 'mask_p1';
    mask_p.appendChild(document.createTextNode("test"));
    mask_p.style.position = "absolute";
    mask_p.style.left =  '20px';
    mask_p.style.top =  '20px';
    mask_p.style.overflow = "hidden";
    mask_p.style.zIndex = "9999";
    mask_p.style.opacity = 0.3;
　　document.body.appendChild(mask_p);

2.Continue to improve

the above The example only displays a watermark somewhere on the page. In actual applications, it is often necessary to cover the page with watermarks

To meet this demand, the following code provides various attributes to the user in a configuration mode. Can be called flexibly according to needs

function watermark(settings) {

    //默认设置
    var defaultSettings={
        watermark_txt:"text",
        watermark_x:20,//水印起始位置x轴坐标
        watermark_y:20,//水印起始位置Y轴坐标
        watermark_rows:20,//水印行数
        watermark_cols:20,//水印列数
        watermark_x_space:100,//水印x轴间隔
        watermark_y_space:50,//水印y轴间隔
        watermark_color:'#000000',//水印字体颜色
        watermark_alpha:0.3,//水印透明度
        watermark_fontsize:'18px',//水印字体大小
        watermark_font:'微软雅黑',//水印字体
        watermark_width:120,//水印宽度
        watermark_height:80,//水印长度
        watermark_angle:15//水印倾斜度数
    };
    //采用配置项替换默认值，作用类似jquery.extend
    if(arguments.length===1&&typeof arguments[0] ==="object" )
    {
        var src=arguments[0]||{};
        for(key in src)
        {
            if(src[key]&&defaultSettings[key]&&src[key]===defaultSettings[key])
                continue;
            else if(src[key])
                defaultSettings[key]=src[key];
        }
    }

    var oTemp = document.createDocumentFragment();

    //获取页面最大宽度
    var page_width = Math.max(document.body.scrollWidth,document.body.clientWidth);
    //获取页面最大长度
    var page_height = Math.max(document.body.scrollHeight,document.body.clientHeight);

    //如果将水印列数设置为0，或水印列数设置过大，超过页面最大宽度，则重新计算水印列数和水印x轴间隔
    if (defaultSettings.watermark_cols == 0 || 　　　　(parseInt(defaultSettings.watermark_x 　　　　+ defaultSettings.watermark_width *defaultSettings.watermark_cols 　　　　+ defaultSettings.watermark_x_space * (defaultSettings.watermark_cols - 1)) 　　　　> page_width)) {
        defaultSettings.watermark_cols = 　　　　　　parseInt((page_width　　　　　　　　　　-defaultSettings.watermark_x　　　　　　　　　　+defaultSettings.watermark_x_space) 　　　　　　　　　　/ (defaultSettings.watermark_width 　　　　　　　　　　+ defaultSettings.watermark_x_space));
        defaultSettings.watermark_x_space = 　　　　　　parseInt((page_width 　　　　　　　　　　- defaultSettings.watermark_x 　　　　　　　　　　- defaultSettings.watermark_width 　　　　　　　　　　* defaultSettings.watermark_cols) 　　　　　　　　　　/ (defaultSettings.watermark_cols - 1));
    }
    //如果将水印行数设置为0，或水印行数设置过大，超过页面最大长度，则重新计算水印行数和水印y轴间隔
    if (defaultSettings.watermark_rows == 0 || 　　　　(parseInt(defaultSettings.watermark_y 　　　　+ defaultSettings.watermark_height * defaultSettings.watermark_rows 　　　　+ defaultSettings.watermark_y_space * (defaultSettings.watermark_rows - 1)) 　　　　> page_height)) {
        defaultSettings.watermark_rows = 　　　　　　parseInt((defaultSettings.watermark_y_space 　　　　　　　　　　　+ page_height - defaultSettings.watermark_y) 　　　　　　　　　　　/ (defaultSettings.watermark_height + defaultSettings.watermark_y_space));
        defaultSettings.watermark_y_space = 　　　　　　parseInt((page_height 　　　　　　　　　　- defaultSettings.watermark_y 　　　　　　　　　　- defaultSettings.watermark_height 　　　　　　　　　　* defaultSettings.watermark_rows) 　　　　　　　　　/ (defaultSettings.watermark_rows - 1));
    }
    var x;
    var y;
    for (var i = 0; i < defaultSettings.watermark_rows; i++) {
        y = defaultSettings.watermark_y + (defaultSettings.watermark_y_space + defaultSettings.watermark_height) * i;
        for (var j = 0; j < defaultSettings.watermark_cols; j++) {
            x = defaultSettings.watermark_x + (defaultSettings.watermark_width + defaultSettings.watermark_x_space) * j;

            var mask_p = document.createElement(&#39;p&#39;);
            mask_p.id = &#39;mask_p&#39; + i + j;
            mask_p.appendChild(document.createTextNode(defaultSettings.watermark_txt));
            //设置水印p倾斜显示
            mask_p.style.webkitTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
            mask_p.style.MozTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
            mask_p.style.msTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
            mask_p.style.OTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
            mask_p.style.transform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
            mask_p.style.visibility = "";
            mask_p.style.position = "absolute";
            mask_p.style.left = x + &#39;px&#39;;
            mask_p.style.top = y + &#39;px&#39;;
            mask_p.style.overflow = "hidden";
            mask_p.style.zIndex = "9999";
            //mask_p.style.border="solid #eee 1px";
            mask_p.style.opacity = defaultSettings.watermark_alpha;
            mask_p.style.fontSize = defaultSettings.watermark_fontsize;
            mask_p.style.fontFamily = defaultSettings.watermark_font;
            mask_p.style.color = defaultSettings.watermark_color;
            mask_p.style.textAlign = "center";
            mask_p.style.width = defaultSettings.watermark_width + &#39;px&#39;;
            mask_p.style.height = defaultSettings.watermark_height + &#39;px&#39;;
            mask_p.style.display = "block";
            oTemp.appendChild(mask_p);
        };
    };
    document.body.appendChild(oTemp);
}

3. Calling method

watermark({ watermark_txt: "测试水印" })//传入动态水印内容

//onload时触发水印绘制
window.onload=function(){
watermark({ watermark_txt: "测试水印" });
};

//onresize时触发水印绘制
window.onresize = function () {
 watermark({ watermark_txt: "测试水印",watermark_width:50 }) 
};

Recommended learning: "javascript basic tutorial"

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