WEB图片水印实现

很多大公司内网都有页面不可见水印，一旦图片截图发送给外部后，可以根据图片不可见水印进行溯源，查出发送人的信息。

原图：(就是下面白色的图片)

PS 打开这个图片，在这个图片上新建图层，填充黑色，混合模式选择是色混合即可。

效果：

在线测试地址 https://www.mwcxs.top/static/testTool/index.html

(function(watermark){
    window.watermarkdivs = [];
    // 加载水印
    var loadMark = function(settings) {
            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:0,//水印行数
                watermark_cols:0,//水印列数
                watermark_x_space:50,//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:0.005,//水印透明度，小于等于0.003,不可恢复到水印。
                watermark_fontsize:'18px',//水印字体
                watermark_font:'微软雅黑',//水印字体
                watermark_150,//水印宽度
                watermark_height:100,//水印长度
                watermark_angle:15,//水印倾斜度数
                // watermark_bg_color:'yellow',
                watermark_bg_alpha:0.5 //加透明度导致隐形水印无法读取
                
            };
            //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();

            if (window.watermarkdivs && window.watermarkdivs.length > 0) {
                document.body.removeChild(document.getElementById("otdivid"));
                window.watermarkdivs = [];
            }

            //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);

            var otdiv = document.getElementById("otdivid");

            //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_div = document.createElement('div');
                    mask_div.id = 'mask_div' + i + j;
                    mask_div.appendChild(document.createTextNode(defaultSettings.watermark_txt));
                    //设置水印div倾斜显示
                    mask_div.style.webkitTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
                    mask_div.style.MozTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
                    mask_div.style.msTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
                    mask_div.style.OTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
                    mask_div.style.transform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
                    mask_div.style.visibility = "";
                    mask_div.style.position = "absolute";
                    //选不中
                    mask_div.style.left = x + 'px';
                    mask_div.style.top = y + 'px';
                    mask_div.style.overflow = "hidden";
                    mask_div.style.zIndex = "9";
                    mask_div.style.pointerEvents = "none";
                    //mask_div.style.border="solid #eee 1px";
                    mask_div.style.opacity = defaultSettings.watermark_alpha;
                    mask_div.style.fontSize = defaultSettings.watermark_fontsize;
                    mask_div.style.fontFamily = defaultSettings.watermark_font;
                    mask_div.style.color = defaultSettings.watermark_color;
                    mask_div.style.textAlign = "center";
                    mask_div.style.width = defaultSettings.watermark_width + 'px';
                    mask_div.style.height = defaultSettings.watermark_height + 'px';
                    mask_div.style.display = "block";
                    mask_div.style.fontWeight = "900";
                    oTemp.appendChild(mask_div);

                };
            };
            document.body.appendChild(oTemp);
        };
    
    watermark.load = function(settings) {
        window.onload = function() {
            loadMark(settings);
        };
        window.onresize = function() {
            loadMark(settings);
        };
    };
    watermark.load({ watermark_txt: "测试水印，1021002301，测试水印，SDAHJDBJJdjsfsc" });
})(window.watermark = {});