const fs = require('fs');

const path = require('path');

const mime = require('mime-types'); //需npm安装

const Koa = require('koa'); //需npm安装

const app = new Koa();

app.use(async (ctx) => {

	let filePath = path.join(__dirname, ctx.url); //图片地址

	let file = null;

	try {

	    file = fs.readFileSync(filePath); //读取文件

	} catch (error) {

		//如果服务器不存在请求的图片，返回默认图片

	    filePath = path.join(__dirname, '/images/default.png'); //默认图片地址

	    file = fs.readFileSync(filePath); //读取文件

	}

	let mimeType = mime.lookup(filePath); //读取图片文件类型

	ctx.set('content-type', mimeType); //设置返回类型

	ctx.body = file; //返回图片

});