'use strict'

var watermark = (className,str,type) => {

	let dom = document.getElementsByClassName(className)

	let canvas = document.createElement('canvas')

	let cxt = canvas.getContext('2d')

	let div = document.createElement('div')

	let imgScale = 0.6

	canvas.width = 200

	if(type == 'text'){

	  cxt.font = '16px Microsoft JhengHei'

	  cxt.fillStyle = 'rgba(200, 200, 200, 0.3)'

	  cxt.textAlign = 'left'

	  cxt.textBaseline = 'Middle'

	  cxt.fillText(str, 10, 50)

	  cxt.clearRect(0, 0, canvas.width, canvas.height);

	   div.style.background = 'url(' + canvas.toDataURL('image/png') + ') left top repeat'

	   drawImage(div,dom)

	}else{

		//创建新的图片对象

		let img = new Image();

		//指定图片的URL

		img.src = str;

		//浏览器加载图片完毕后再绘制图片

		img.onload = function() {

			//cxt.drawImage(img,0,0);

			cxt.rotate(-20 * Math.PI / 180)

			let whScale = img.width / img.height

			cxt.clearRect(0, 0, canvas.width, canvas.height);

			 cxt.drawImage(img, //规定要使用的图像、画布或视频。

							0, 0, //开始剪切的 x 坐标位置。

							img.width, img.height,  //被剪切图像的高度。

							0, 50,//在画布上放置图像的 x 、y坐标位置。

							img.width * imgScale, img.height * imgScale  //要使用的图像的宽度、高度

							)

			div.style.opacity = 0.3

			div.style.background = 'url(' + canvas.toDataURL('image/png') + ') left top repeat'

			drawImage(div,dom)

		}

	}

}

var drawImage = function (div,dom) {

	div.style.pointerEvents = 'none'

	  div.className = 'weterbox' //样式名

	  div.style.top = 0

	  div.style.left = 0

	  div.style.position = 'absolute'

	  div.style.zIndex = '100000'

	  div.style.width = '100%'

	  div.style.height = '100%'

	//console.log(dom)

	if( dom.length > 0){

		for(let i = 0; i< dom.length;i++){

			let child = dom[i].getElementsByClassName('weterbox')

			if(child.length > 0){

				dom[i].removeChild(child[0])

			}

			dom[i].appendChild(div.cloneNode(true))

		//	console.log(i,dom[i])

		}

	}

}

export default watermark

watermark('需要添加水印的div元素的className','水印图片路径')
 

watermark('需要添加水印的div元素的className','水印文字'，'text')

.viewWeb{

		position: relative;

	}