水印專案的實現以及兩種實現方案的選優
水印專案我們提出了兩種解決方案
一、用shadow dom實現
1、基本思路
通過attachShadow這個方法生成一個shadow root 即shadow的根節點,然後在這個根節點下面通過迴圈語句新增水印,利用position為absolute進行排版,使其鋪滿容器
show me the code:
(function (root, factory) {
if (typeof define === 'function' && define.amd) {
/*AMD. Register as an anonymous module.
*define([], factory); */
define([], factory());
} else if (typeof module === 'object' && module.exports) {
/*Node. Does not work with strict Commonjs , but
// only Commonjs-like environments that support module.exports,
// like Node.*/
module.exports = factory();
} else {
/*Browser globals (root is window)*/
root['watermark'] = factory();
}
}(this, function () {
/*Just return a value to define the module export.*/
let watermark = {};
/*載入水印*/
let loadMark = function () {
let defaultSettings = {
watermark_id: 'wm_div _id', //水印總體的id
watermark_prefix: 'mask_div_id', //小水印的id字首
watermark_txt: "測試水印", //水印的內容
watermark_x: 20, //水印起始位置x軸座標
watermark_y: 40, //水印起始位置Y軸座標
watermark_rows: 0, //水印行數
watermark_cols: 0, //水印列數
watermark_x_space: 100, //水印x軸間隔
watermark_y_space: 50, //水印y軸間隔
watermark_font: '微軟雅黑', //水印字型
watermark_color: 'black', //水印字型顏色
watermark_fontsize: '18px', //水印字型大小
watermark_alpha: 0.15, //水印透明度,要求設定在大於等於0.005
watermark_width: 100, //水印寬度
watermark_height: 100, //水印長度
watermark_angle: 15, //水印傾斜度數
watermark_parent_selector: null, //水印外掛掛載的父元素選取器,不輸入則預設掛在body上
need_adapt_screen: false, // 是否根據螢幕的解析度等比變化每個水印的寬度和字型大小
watermark_width_proportion: 15, // 每個水印寬度自適應螢幕變化的等比放大或縮小的值
watermark_fontsize_proportion: 95, // 每個水印字型大小自適應螢幕變化的等比放大或縮小的值
};
let watermark_parent_node = null //水印外掛掛載的父元素element,不輸入則預設掛在body上
let setting = arguments[0] || {};
/*採用配置項替換預設值,作用類似jquery.extend*/
if (arguments.length === 1 && typeof arguments[0] === "object") {
for (let key in setting) {
if (setting[key] && defaultSettings[key] && setting[key] === defaultSettings[key]) continue;
/*veronic: resolution of watermark_angle=0 not in force*/
else if (setting[key] || setting[key] === 0) defaultSettings[key] = setting[key];
}
}
/* 設定水印的容器 */
if (defaultSettings.watermark_parent_selector) {
watermark_parent_node = document.querySelector(defaultSettings.watermark_parent_selector)
} else {
watermark_parent_node = document.body
}
/*如果元素存在則移除*/
let watermark_element = document.getElementById(defaultSettings.watermark_id);
if (watermark_element) {
let _parentElement = watermark_element.parentNode;
if (_parentElement) {
_parentElement.removeChild(watermark_element);
}
}
/*獲取水印的起始位置*/
let page_offsetTop = 0;
let page_offsetLeft = 0;
page_offsetTop = watermark_parent_node.offsetTop || 0;
page_offsetLeft = watermark_parent_node.offsetLeft || 0;
page_width = watermark_parent_node.offsetWidth - defaultSettings.watermark_width / 2 || 0;
page_height = (Math.max(watermark_parent_node.offsetHeight, watermark_parent_node.scrollHeight) - defaultSettings.watermark_height / 2) || 0;
defaultSettings.watermark_x = defaultSettings.watermark_x + page_offsetLeft;
defaultSettings.watermark_y = defaultSettings.watermark_y + page_offsetTop;
/*建立水印外殼div*/
let otdiv = document.getElementById(defaultSettings.watermark_id);
let shadowRoot = null;
if (!otdiv) {
otdiv = document.createElement('div');
/*建立shadow dom*/
otdiv.id = defaultSettings.watermark_id;
otdiv.style.pointerEvents = "none";
/*判斷瀏覽器 是否支援attachShadow方法*/
if (typeof otdiv.attachShadow === 'function') {
shadowRoot = otdiv.attachShadow({mode: 'open'});
} else if (typeof otdiv.createShadowRoot === 'function') {
shadowRoot = otdiv.createShadowRoot();
} else {
shadowRoot = otdiv;
}
watermark_parent_node.appendChild(otdiv)
} else if (otdiv.shadowRoot) {
shadowRoot = otdiv.shadowRoot;
}
// shadow內加個容器
let shadowOutDiv = document.createElement('div')
shadowOutDiv.id = 'shadowContainer'
shadowRoot.appendChild(shadowOutDiv)
/*如果將水印列數設定為0,或水印列數設定過大,超過頁面最大寬度,則重新計算水印列數和水印x軸間隔*/
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 + page_offsetLeft) / (defaultSettings.watermark_width + defaultSettings.watermark_x_space));
defaultSettings.watermark_x_space = parseInt((page_width - defaultSettings.watermark_x + page_offsetLeft - defaultSettings.watermark_width * defaultSettings.watermark_cols) / (defaultSettings.watermark_cols - 1));
}
/*如果將水印行數設定為0,或水印行數設定過大,超過頁面最大長度,則重新計算水印行數和水印y軸間隔*/
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((page_height - defaultSettings.watermark_y + page_offsetTop) / (defaultSettings.watermark_height + defaultSettings.watermark_y_space));
defaultSettings.watermark_y_space = parseInt(((page_height - defaultSettings.watermark_y + page_offsetTop) - defaultSettings.watermark_height * defaultSettings.watermark_rows) / (defaultSettings.watermark_rows - 1));
}
let x;
let y;
for (let i = 0; i < defaultSettings.watermark_rows; i++) {
y = defaultSettings.watermark_y + (defaultSettings.watermark_y_space + defaultSettings.watermark_height) * i;
for (let j = 0; j < defaultSettings.watermark_cols; j++) {
x = defaultSettings.watermark_x + (defaultSettings.watermark_width + defaultSettings.watermark_x_space) * j;
let mask_div = document.createElement('div');
let oText = document.createTextNode(defaultSettings.watermark_txt);
mask_div.appendChild(oText);
/*設定水印相關屬性start*/
mask_div.id = defaultSettings.watermark_prefix + i + j;
/*設定水印div傾斜顯示*/
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";
/*選不中*/
mask_div.style.left = x + 'px';
mask_div.style.top = y + 'px';
mask_div.style.overflow = "hidden";
mask_div.style.zIndex = "9999999";
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['-ms-user-select'] = "none";
/*設定水印相關屬性end*/
shadowOutDiv.appendChild(mask_div);
}
}
};
/*初始化水印,新增load和resize事件*/
watermark.init = function (settings) {
window.addEventListener('load', function () {
loadMark(settings);
});
window.addEventListener('resize', function () {
loadMark(settings);
});
window.addEventListener('DOMContentLoaded', function () {
loadMark(settings);
});
};
/*手動載入水印*/
watermark.load = function (settings) {
loadMark(settings);
observerDomReloadMark(settings)
};
return watermark;
}))
2、優化
但是畢竟水印是有關安全方面的,如果別人開啟開發者模式很輕鬆的就水印的內容更改甚至完全刪除,所以不能就這麼完事了。我們需要監聽DOM的變化,判斷如果使用者通過開發者工具手動修改了水印的dom,我們就重新渲染水印,實現水印不能手動進行了修改。
思路:通過mutationObsever監聽DOM的變化,判斷是否是水印部分的dom 變化,如果是則重新渲染
show me the code:
/* 監聽DOM的變化,防止手動刪除 */
let observerDomReloadMark = (settings) => {
// Select the node that will be observed for mutations
let observer_node = document.querySelector('#shadowContainer')
// Options for the observer (which mutations to observe)
let config = {
attributes: true,
childList: true,
subtree: true
};
// Callback function to execute when mutations are observed
const mutationCallback = (mutationsList) => {
// for (let mutation of mutationsList) {
// let type = mutation.type;
// switch (type) {
// case "childList":
// console.log("A child node has been added or removed.");
// break;
// case "attributes":
// console.log(`The ${mutation.attributeName} attribute was modified.`);
// break;
// case "subtree":
// console.log(`The subtree was modified.`);
// break;
// default:
// break;
// }
// }
// loadMark(settings)
console.log(2222)
};
// Create an observer instance linked to the callback function
let observer = new MutationObserver(mutationCallback);
// Start observing the target node for configured mutations
observer.observe(observer_node, config);
// Later, you can stop observing
// observer.disconnect();
}
這個方法看起來完美,然而現實很殘酷,當我們再瀏覽器中看效果的時候發現mutationObsever不能監聽shadow的變化,what? 查資料後發現shadow是獨立於dom樹的,相當於被隔離起來的dom。既然如此那就放棄裝逼吧,還是老老實實用正常的dom實現吧,有多少個水印就生成多個水印的dom,這必要會導致效能問題。好吧,我們還是再另尋他法。
二、canvas繪圖
1、基本思路
通過canvas把單個水印繪製出來,用toDataURL方法生成圖片的base64編碼,放在水印容器的background-image:url()裡面,背景圖片會自動鋪滿整個容器。思想比第一種方案簡單很多。
show me the code:
var canvas = document.createElement('canvas')
canvas.id = 'canvas'
canvas.width = defaultSettings.watermark_width // 單個水印的寬度
canvas.height = defaultSettings.watermark_height // 單個水印的高度
var ctx = canvas.getContext('2d')
ctx.font = 'normal 12px Microsoft Yahei' // 設定樣式
ctx.fillStyle = 'rgba(112, 113, 114, 0.2)' // 水印字型顏色
ctx.translate(canvas.width/2,canvas.height/2)
ctx.rotate((defaultSettings.watermark_angle * Math.PI) / 180) // 水印偏轉角度
ctx.translate(-canvas.width/2,-canvas.height/2)
ctx.fillText(defaultSettings.watermark_txt, 30, 20)
var src = canvas.toDataURL('image/png')
/* 設定水印的容器 */
var watermark_parent_node = null
if (defaultSettings.watermark_parent_selector) {
watermark_parent_node = document.querySelector(defaultSettings.watermark_parent_selector)
} else {
watermark_parent_node = document.body
}
watermark_parent_node.style.pointerEvents = 'none'
// 判斷容器是否已經設定了backgroundImage屬性值
if (!watermark_parent_node.style.backgroundImage) {
watermark_parent_node.style.backgroundImage = 'URL(' + src + ')'
} else {
watermark_parent_node.style.backgroundImage = watermark_parent_node.style.backgroundImage + ', URL(' + src + ')'
}
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2、優化
優化思路和第一種方案一樣,只不過這種方案的好處就是可以直接監聽到變化。
三、兩種方案的對比
方案 | 優點 | 缺點 |
shadow DOM | 1、低耦合,shadow dom與原先的DOM樹隔離,不會影響到系統本有的功能。 |
1、shadow DOM不能夠被監聽到 2、水印文案及DOM被篡改的成本較低 3、實現邏輯比較複雜 |
canvas繪圖 |
1、實現邏輯比較清晰 2、水印資料生成圖片,使用者想篡改比較難 3、水印被篡改能夠被監聽到 |
1、水印圖片是被放在background-image裡面的,如果原先在class裡面設定了background-image屬性的話會被覆蓋掉 |