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使用html2canvas实现浏览器截图的示例代码

来源:  2018-08-21 19:41:24    评论:0点击:

使用html2canvas实现浏览器截图,必须在服务器环境下才能实现。

作用

html2canvas可以通过纯JS对浏览器端经行截屏,但截图的精确度还有待提高,部分css不可识别,所以在canvas中不能完美呈现原画面样式

 

支持的浏览器

  1. Firefox 3.5+
  2. Google Chrome
  3. Opera 12+
  4. IE9+
  5. Safari 6+

基本语法

/*多行溢出省略就不行,只能超出隐藏了*/
     .book_inf{
            position: relative; 
            overflow : hidden;
            text-overflow: ellipsis;
            display: -webkit-box;
            -webkit-line-clamp: 2;
            -webkit-box-orient: vertical;
        }
/*参数:
* #screenshots 所需要截图的元素id,截图后要执行的函数,
* backgroundColor 配置项背景色
* canvas为截图后返回的最后一个canvas
*/
function screenshotsImg(){
       html2canvas(document.querySelector("#screenshots"),{
            backgroundColor: 'transparent',// 设置背景透明
        }).then(canvas => {
            canvasTurnImg(canvas) //保存的图片格式转换方法
        });
    }		
 

可用配置项

 

参数名称 类型 默认值 描述
allowTaint boolean false Whether to allow cross-origin images to taint the canvas---允许跨域
background string #fff Canvas background color, if none is specified in DOM. Set undefined for transparent---canvas的背景颜色,如果没有设定默认白色此处被坑,我改为backgroundColor可用
height number null Define the heigt of the canvas in pixels. If null, renders with full height of the window.---canvas高度设定
letterRendering boolean false Whether to render each letter seperately. Necessary if letter-spacing is used.---在设置了字间距的时候有用
logging boolean false Whether to log events in the console.---在console.log()中输出信息
proxy string undefined Url to the proxy which is to be used for loading cross-origin images. If left empty, cross-origin images won't be loaded.---代理地址
taintTest boolean true Whether to test each image if it taints the canvas before drawing them---是否在渲染前测试图片
timeout number 0 Timeout for loading images, in milliseconds. Setting it to 0 will result in no timeout.---图片加载延迟,默认延迟为0,单位毫秒
width number null Define the width of the canvas in pixels. If null, renders with full width of the window.---canvas宽度
useCORS boolean false Whether to attempt to load cross-origin images as CORS served, before reverting back to proxy--跨域代理

设置图片格式

1、从canvas中直接提取图片元数据


 

1、从canvas中直接提取图片元数据
 
	
// 图片导出为 png 格式
      var type = 'png';
      var imgData = canvas.toDataURL(type);

//2、将mime-type改为image/octet-stream,强制让浏览器直接download
 
	
/**
 * 获取mimeType
 * @param  {String} type the old mime-type
 * @return the new mime-type
 */
var _fixType = function(type) {
    type = type.toLowerCase().replace(/jpg/i, 'jpeg');
    var r = type.match(/png|jpeg|bmp|gif/)[0];
    return 'image/' + r;
};
    
// 加工image data,替换mime type
imgData = imgData.replace(_fixType(type),'image/octet-stream');

//3、图片download到本地
 
/**
 * 在本地进行文件保存
 * @param  {String} data     要保存到本地的图片数据
 * @param  {String} filename 文件名
 */
var saveFile = function(data, filename){
    var save_link = document.createElementNS('http://www.w3.org/1999/xhtml', 'a');
    save_link.href = data;
    save_link.download = filename;
    
    var event = document.createEvent('MouseEvents');
    event.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
    save_link.dispatchEvent(event);
};
    
// 下载后的文件名
var filename = 'baidufe_' + (new Date()).getTime() + '.' + type;
// download
saveFile(imgData,filename);

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