js實現前端水印功能

(function(watermark) {
	window.watermarkdivs = [];
	// 加載水印
	var loadMark = function(settings) {
		var defaultSettings = {
			watermark_txt: settings.watermark_txt ? settings.watermark_txt : '請輸入自定義內容(50字以內)',
			watermark_x: settings.watermark_x ? settings.watermark_x : 20, //水印起始位置x軸坐標
			watermark_y: settings.watermark_y ? settings.watermark_y : 20, //水印起始位置Y軸坐標
			watermark_rows: settings.watermark_rows ? settings.watermark_rows : 0, //水印行數
			watermark_cols: settings.watermark_cols ? settings.watermark_cols : 0, //水印列數
			watermark_x_space: settings.watermark_x_space ? settings.watermark_x_space : 50, //水印x軸間隔
			watermark_y_space: settings.watermark_y_space ? settings.watermark_y_space : 50, //水印y軸間隔
			watermark_color: settings.watermark_color ? settings.watermark_color : '#000000', //水印字體顏色
			watermark_alpha: settings.watermark_alpha ? settings.watermark_alpha : 0.05, //水印透明度，要求設置在大於等於0.005
			watermark_fontsize: settings.watermark_fontsize ? settings.watermark_fontsize : '18px', //水印字體大小
			watermark_font: settings.watermark_font ? settings.watermark_font : '宋體', //水印字體
			watermark_width: settings.watermark_width ? settings.watermark_width : 150, //水印寬度
			watermark_height: settings.watermark_height ? settings.watermark_height : 100, //水印長度
			watermark_angle: settings.watermark_angle ? settings.watermark_angle : 15, //水印傾斜度數
			watermark_bg_alpha: settings.watermark_bg_alpha ? settings.watermark_bg_alpha : 0.5, //加透明度導致隱形水印無法讀取
		}
		//采用配置項替換默認值，作用類似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];
			}
		}

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

		//獲取頁面最大寬度
		var page_width = Math.max(document.body.scrollWidth, document.body.clientWidth) - parseInt(defaultSettings.watermark_width / 2);
		//獲取頁面最大長度
		// var page_height = Math.max(document.body.scrollHeight,document.body.clientHeight);
		// 當前獲取某個需要水印區域的div的高度waterMarkImgAreaId為div的id
        var page_height = $("#waterMarkImgAreaId").outerHeight() - 10;

		// 創建文檔碎片
		var oTemp = document.createDocumentFragment();
		//創建水印外殼div
		var otdiv = document.getElementById("otdivid");
		if (!otdiv) {
			otdiv = document.createElement('div');
			otdiv.id = "otdivid";
			otdiv.style.pointerEvents = "none";
			document.body.appendChild(otdiv);
		}

		//如果將水印列數設置為0，或水印列數設置過大，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 + 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));
		}
		//如果將水印行數設置為0，或水印行數設置過大，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((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');
				var oText = document.createTextNode(defaultSettings.watermark_txt);
				mask_div.appendChild(oText);
				// 設置一張水印相關屬性start
				mask_div.id = 'mask_div' + i + j;
				//設置水印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 = "9999";
				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.wordWrap = "break-word";
				//設置一張水印相關屬性end
				//附加到文檔碎片中
				otdiv.appendChild(mask_div);
                //控制頁面大小變化時水印字體
				window.watermarkdivs.push(otdiv); 
			};
		};
		//一次性添加到document中
		document.body.appendChild(oTemp);
	};
    // 水印加載事件
	watermark.load = function(settings) {
		loadMark(settings);
        // 監聽load事件load 僅用於檢測一個完全加載的頁面，頁面的html、css、js、圖片等資源都已經加載完之后才會觸發 load 事件
		// window.addEventListener('load', function() {
		//	loadMark(settings)
		//})
        // 當初始的 HTML 文檔被完全加載和解析完成之后，DOMContentLoaded 事件被觸發，而無需等待樣式表、圖像和子框架的完成加載
		//window.addEventListener('DOMContentLoaded', function() {
		//	loadMark(settings)
		//})
	};
    // 水印移除事件
	watermark.remove = function() {
		removeMark();
	}
    // 移除水印
	var removeMark = function() {
		if (window.watermarkdivs && window.watermarkdivs.length > 0) {
			document.body.removeChild(document.getElementById('otdivid'))
			window.watermarkdivs = []
		}
	}
})(window.watermark = {});