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
/*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;
}支持的浏览器
Firefox 3.5+
Google Chrome
Opera 12+
IE9+
Safari 6+
基本语法
/*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
// 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
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