在文章中添加图片时，由于图片很大，导致浏览文章时严重影响用户体验，因此需要在上传是对图片进行压缩处理
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0" name="viewport">
<title>移动端图片压缩上传demo</title>
<style>
* {
margin: 0;
padding: 0;
}
li {
list-style-type: none;
}
a,
input {
outline: none;
-webkit-tap-highlight-color: rgba(0, 0, 0, 0);
}
#choose {
display: none;
}
canvas {
100%;
border: 1px solid #000000;
}
#upload {
display: block;
margin: 10px;
height: 60px;
text-align: center;
line-height: 60px;
border: 1px solid;
border-radius: 5px;
cursor: pointer;
}
.touch {
background-color: #ddd;
}
.img-list {
margin: 10px 5px;
}
.img-list li {
position: relative;
display: inline-block;
100px;
height: 100px;
margin: 5px 5px 20px 5px;
border: 1px solid rgb(100, 149, 198);
background: #fff no-repeat center;
background-size: cover;
}
.progress {
position: absolute;
100%;
height: 20px;
line-height: 20px;
bottom: 0;
left: 0;
background-color: rgba(100, 149, 198, .5);
}
.progress span {
display: block;
0;
height: 100%;
background-color: rgb(100, 149, 198);
text-align: center;
color: #FFF;
font-size: 13px;
}
.size {
position: absolute;
100%;
height: 15px;
line-height: 15px;
bottom: -18px;
text-align: center;
font-size: 13px;
color: #666;
}
.tips {
display: block;
text-align: center;
font-size: 13px;
margin: 10px;
color: #999;
}
.pic-list {
margin: 10px;
line-height: 18px;
font-size: 13px;
}
.pic-list a {
display: block;
margin: 10px 0;
}
.pic-list a img {
vertical-align: middle;
max- 30px;
max-height: 30px;
margin: -4px 0 0 10px;
}
</style>
</head>
<body>
<input type="file" id="choose" accept="image/*" multiple>
<ul class="img-list"></ul>
<a id="upload">上传图片</a>
<span class="tips">只允许上传jpg、png及gif</span>
<script src="../../public/jquery-2.1.1.min.js"></script>
<script>
var filechooser = document.getElementById("choose");
// 用于压缩图片的canvas
var canvas = document.createElement("canvas");
var ctx = canvas.getContext('2d');
// 瓦片canvas
var tCanvas = document.createElement("canvas");
var tctx = tCanvas.getContext("2d");
var maxsize = 300 * 1024; // 最大 300kb
$("#upload").on("click", function () {
filechooser.click();
})
.on("touchstart", function () {
$(this).addClass("touch")
})
.on("touchend", function () {
$(this).removeClass("touch")
});
filechooser.onchange = function () {
if (!this.files.length) return;
var files = Array.prototype.slice.call(this.files);
if (files.length > 9) {
alert("最多同时只可上传9张图片");
return;
}
files.forEach(function (file, i) {
if (!//(?:jpeg|png|gif)/i.test(file.type)) return;
var reader = new FileReader();
var li = document.createElement("li");
// 获取原图大小
var size = file.size / 1024 > 1024 ? (~~(10 * file.size / 1024 / 1024)) / 10 + "MB" : ~~(
file.size / 1024) + "KB";
li.innerHTML = '<div class="progress"><span></span></div><div class="size">' + size +
'</div>';
$(".img-list").append($(li));
reader.onload = function () {
var result = this.result;
var img = new Image();
img.src = result;
$(li).css("background-image", "url(" + result + ")");
//如果图片大小小于300kb，则直接上传
if (result.length <= maxsize) {
img = null;
upload(result, file.type);
return;
}
// 图片加载完毕之后进行压缩，然后上传
if (img.complete) {
callback();
} else {
img.onload = callback;
}
function callback() {
var data = compress(img);
upload(data, file.type);
img = null;
}
};
reader.readAsDataURL(file);
})
};
// 使用canvas对大图片进行压缩
function compress(img) {
var initSize = img.src.length;
var width = img.width;
var height = img.height;
//如果图片大于四百万像素，计算压缩比并将大小压至400万以下
var ratio;
if ((ratio = width * height / 4000000) > 1) {
ratio = Math.sqrt(ratio);
width /= ratio;
height /= ratio;
} else {
ratio = 1;
}
canvas.width = width;
canvas.height = height;
// 铺底色
ctx.fillStyle = "#fff";
ctx.fillRect(0, 0, canvas.width, canvas.height);
//如果图片像素大于100万则使用瓦片绘制
var count;
if ((count = width * height / 1000000) > 1) {
count = ~~(Math.sqrt(count) + 1); //计算要分成多少块瓦片
// 计算每块瓦片的宽和高
var nw = ~~(width / count);
var nh = ~~(height / count);
tCanvas.width = nw;
tCanvas.height = nh;
for (var i = 0; i < count; i++) {
for (var j = 0; j < count; j++) {
tctx.drawImage(img, i * nw * ratio, j * nh * ratio, nw * ratio, nh * ratio, 0, 0, nw, nh);
ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh);
}
}
} else {
ctx.drawImage(img, 0, 0, width, height);
}
// 动态计算压缩比，压缩到最接近 maxsize的状态
const range = +(maxsize / initSize).toFixed(1)
var ndata = canvas.toDataURL('image/jpeg', range);
console.log('压缩前：' + initSize);
console.log('压缩后：' + ndata.length);
console.log('压缩率：' + ~~(100 * (initSize - ndata.length) / initSize) + "%");
tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0;
return ndata;
}
// 图片上传，将base64的图片转成二进制对象，塞进formdata上传
function upload(basestr, type) {
console.log(basestr.length / 1024, type, dataURItoBlob(basestr))
}
function dataURItoBlob(dataURI) {
var binary = atob(dataURI.split(',')[1]);
var array = [];
for (var i = 0; i < binary.length; i++) {
array.push(binary.charCodeAt(i));
}
return new Blob([new Uint8Array(array)], {
type: 'image/jpeg'
});
}
</script>
</body>
</html>
服务器端代码
/*
*移动端图片压缩上传功能后台
*/
"use strict";
var fs = require('fs');
var router = require("../router");
//var FormParser = require("./formParser");
var formidable = require('formidable');
var path = require('path');
var fileSaveDir = path.join(STATIC_PATH, 'upload');
router.setMap({
"uindex_2": path.join(__dirname, "./index_2.html"),
"cupload": cupload
});
function cupload(req, res) {
if (!fs.existsSync(fileSaveDir)) {
fs.mkdirSync(fileSaveDir)
}
var form = new formidable.IncomingForm();
var responseData = [];
form.uploadDir = fileSaveDir;
form.type = true;
form.keepExtensions = true;
form.parse(req, function(err, fields, files){
if(!err) {
Object.keys(files).forEach(function(key){
var file = files[key];
var filename = path.basename(file.path);
//每张图片给予一分钟保存时间
setTimeout(function() {
if (!fs.existsSync(file.path)) return;
console.log("x1B[33m删除文件" + filename + "x1B[0m");
fs.unlinkSync(file.path);
}, 60 * 1000);
// 塞入响应数据中
responseData.push({
type: file.type,
name: filename,
path: '/public/upload/' + filename,
size: file.size / 1024 > 1024 ? (~~(10 * file.size / 1024 / 1024)) / 10 + "MB" : ~~(file.size / 1024) + "KB"
});
});
} else {
console.warn(err);
}
res.writeHead(200);
res.end(JSON.stringify(responseData));
});
}
代码出自 https://github.com/whxaxes/node-test， 略微做了调整