移动端图片压缩上传功能如何实现？
做移动端开发的时候，form里面的file后台经常获取不到，用foemdata也拿不到
找到了一个formdata的脚本
我要评论
<!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{width: 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;width: 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;width: 100%;height: 20px;line-height: 20px;bottom: 0;left: 0;background-color:rgba(100,149,198,.5);}
.progress span{display: block;width: 0;height: 100%;background-color:rgb(100,149,198);text-align: center;color: #fff;font-size: 13px;}
.size{position: absolute;width: 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-width: 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>
<div class="pic-list">
你上传的图片(图片有效期为1分钟)：
</div>
<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 = 100 * 1024;
$("#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");
// 获取图片大小
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100kb，则直接上传
if (result.length <= maxsize) {
img = null;
upload(result, file.type, $(li));
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, $(li));
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);
}
//进行最小压缩
var ndata = canvas.todataurl('image/jpeg', 0.1);
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, $li) {
var text = window.atob(basestr.split(",")[1]);
var buffer = new uint8array(text.length);
var pecent = 0, loop = null;
for (var i = 0; i < text.length; i++) {
buffer[i] = text.charcodeat(i);
}
var blob = getblob([buffer], type);
var xhr = new xmlhttprequest();
var formdata = getformdata();
formdata.append('imagefile', blob);
xhr.open('post', '/cupload');
xhr.onreadystatechange = function() {
if (xhr.readystate == 4 && xhr.status == 200) {
var jsondata = json.parse(xhr.responsetext);
var imagedata = jsondata[0] || {};
var text = imagedata.path ? '上传成功' : '上传失败';
console.log(text + '：' + imagedata.path);
clearinterval(loop);
//当收到该消息时上传完毕
$li.find(".progress span").animate({'width': "100%"}, pecent < 95 ? 200 : 0, function() {
$(this).html(text);
});
if (!imagedata.path) return;
$(".pic-list").append('<a href="' + imagedata.path + '" rel="external nofollow" >' + imagedata.name + '（' + imagedata.size + '）<img src="' + imagedata.path + '" /></a>');
}
};
//数据发送进度，前50%展示该进度
xhr.upload.addeventlistener('progress', function(e) {
if (loop) return;
pecent = ~~(100 * e.loaded / e.total) / 2;
$li.find(".progress span").css('width', pecent + "%");
if (pecent == 50) {
mockprogress();
}
}, false);
//数据后50%用模拟进度
function mockprogress() {
if (loop) return;
loop = setinterval(function() {
pecent++;
$li.find(".progress span").css('width', pecent + "%");
if (pecent == 99) {
clearinterval(loop);
}
}, 100)
}
xhr.send(formdata);
}
/**
* 获取blob对象的兼容性写法
* @param buffer
* @param format
* @returns {*}
*/
function getblob(buffer, format) {
try {
return new blob(buffer, {type: format});
} catch (e) {
var bb = new (window.blobbuilder || window.webkitblobbuilder || window.msblobbuilder);
buffer.foreach(function(buf) {
bb.append(buf);
});
return bb.getblob(format);
}
}
/**
* 获取formdata
*/
function getformdata() {
var isneedshim = ~navigator.useragent.indexof('android')
&& ~navigator.vendor.indexof('google')
&& !~navigator.useragent.indexof('chrome')
&& navigator.useragent.match(/applewebkit\/(\d+)/).pop() <= 534;
return isneedshim ? new formdatashim() : new formdata()
}
/**
* formdata 补丁, 给不支持formdata上传blob的android机打补丁
* @constructor
*/
function formdatashim() {
console.warn('using formdata shim');
var o = this,
parts = [],
boundary = array(21).join('-') + (+new date() * (1e16 * math.random())).tostring(36),
oldsend = xmlhttprequest.prototype.send;
this.append = function(name, value, filename) {
parts.push('--' + boundary + '\r\ncontent-disposition: form-data; name="' + name + '"');
if (value instanceof blob) {
parts.push('; filename="' + (filename || 'blob') + '"\r\ncontent-type: ' + value.type + '\r\n\r\n');
parts.push(value);
}
else {
parts.push('\r\n\r\n' + value);
}
parts.push('\r\n');
};
// override xhr send()
xmlhttprequest.prototype.send = function(val) {
var fr,
data,
oxhr = this;
if (val === o) {
// append the final boundary string
parts.push('--' + boundary + '--\r\n');
// create the blob
data = getblob(parts);
// set up and read the blob into an array to be sent
fr = new filereader();
fr.onload = function() {
oldsend.call(oxhr, fr.result);
};
fr.onerror = function(err) {
throw err;
};
fr.readasarraybuffer(data);
// set the multipart content type and boudary
this.setrequestheader('content-type', 'multipart/form-data; boundary=' + boundary);
xmlhttprequest.prototype.send = oldsend;
}
else {
oldsend.call(this, val);
}
};
}
</script>
</body>
</html>
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