目标实现：
1、选择图片， 前端预览效果
2、图片大于1.2M的时候， 对图片进行压缩
3、以表单的形式上传图片
4、图片删除
预览效果图：
代码说明：
1、input:file选择图片
<!-- html部分 -->
<ul id="preview" class="clear">
<li class="fl">
<img src="/images/audition/icon_upload.png">
<input id="fileImage" type="file" name="file[]" multiple />
<div class="num">0/4</div>
</li>
</ul>
var imgId = 0; //图片id标志, 方便删除预览图片 /* 选择图片 */
function choosePic() {
$('#fileImage').change(function() {
var files = this.files,
len = $('#preview').find('.pic').length;
if (len + files.length > 4) {
showTip('最多只能上传4张图片哦~');
return;
}
for (var i = 0; i < files.length; i++) {
var file = files[i];
if (file.type.indexOf("image") == 0) {
if (file.size >= 1024 * 1024 * 3) {
showTip('图片大小过大，应小于3M');
} else {
showPic(file); //图片预览
}
} else {
showTip('文件"' + file.name + '"不是图片类型')
break;
}
}
});
}
2、图片预览（base64）
/* 渲染图片 */
function showPic(file) {
var html = '',
$wap = $('#preview'),
reader = new FileReader();
reader.readAsDataURL(file);
reader.onload = function(e) {
var image_base64 = this.result; html = '<li class="fl pic" id="imgItem_' + imgId + '">' +
'<img src="' + image_base64 + '" alt="">' +
'<i class="del-img"></i>' +
'</li>';
imgId++;
$wap.append(html);
$('#fileImage').next().text($wap.find('.pic').length + '/4'); //图片压缩上传，大于1.2M压缩图片
if (file.size / 1024 > 1024 * 1.2) {
dealImage(image_base64, {
quality: 0.5
}, function(base64Codes) {
var bl = processData(base64Codes, file.type);
uploadPic(bl, imgId);
});
} else {
uploadPic(file, imgId);
}
}
}
3、图片压缩
/**
* 图片压缩（利用canvas）
* @param path 图片路径
* @param obj 压缩配置width,height,quality，不传则按比例压缩
* @param callback 回调函数
*/
function dealImage(path, obj, callback) {
var img = new Image();
img.src = path;
img.onload = function() {
var that = this;
// 默认按比例压缩
var w = that.width,
h = that.height,
scale = w / h;
w = obj.width || w;
h = obj.height || (w / scale); //生成canvas
var canvas = document.createElement('canvas'),
ctx = canvas.getContext('2d');
canvas.width = w;
canvas.height = h;
ctx.drawImage(that, 0, 0, w, h); // 默认图片质量为0.7
var quality = 0.7;
if (obj.quality && obj.quality <= 1 && obj.quality > 0) {
quality = obj.quality;
} // 回调函数返回base64的值
var base64 = canvas.toDataURL('image/jpeg', quality);
callback(base64);
}
}
压缩后的文件是base64格式， 我们希望用file图片的形式上传
/* 将以base64的图片url数据转换为Blob */
function processData(dataUrl, type) {
var binaryString = window.atob(dataUrl.split(',')[1]),
arrayBuffer = new ArrayBuffer(binaryString.length),
intArray = new Uint8Array(arrayBuffer);
for (var i = 0, j = binaryString.length; i < j; i++) {
intArray[i] = binaryString.charCodeAt(i);
} var data = [intArray], blob; try {
blob = new Blob(data);
} catch (e) {
window.BlobBuilder = window.BlobBuilder ||
window.WebKitBlobBuilder ||
window.MozBlobBuilder ||
window.MSBlobBuilder;
if (e.name === 'TypeError' && window.BlobBuilder) {
var builder = new BlobBuilder();
builder.append(arrayBuffer);
blob = builder.getBlob(type);
} else {
showTip('版本过低，不支持图片压缩上传');
}
}
return blob;
}
4、图片上传
/* 上传图片 */
function uploadPic(file, id) {
var formData = new FormData();
formData.append('img', file);
$.ajax({
url: '/upload',
type: 'post',
dataType: 'json',
data: formData,
contentType: false,
processData: false,
success: function(res){
if(res.respCode == 1000) {
$('#imgItem_' + id).find('.del-img').attr('data-src', res.data.src);
}else {
showTip('文件上传失败！');
}
}
});
}
5、其他
function showTip(str) {
//TODO:信息提示
console.log(str);
}
/* 删除图片 */
function delPic() {
var $wap = $('#preview');
$wap.on('click', '.del-img', function() {
//TODO:从数据库删除图片
$(this).parent().remove();
$('#fileImage').next().text($wap.find('.pic').length + '/4');
});
}
源码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>前端图片预览压缩上传</title>
<style>
.clear::after {
content: '';
clear: both;
display: block;
}
.fl {
float: left;
}
.list-img li {
position: relative;
margin-right: 10px;
list-style: none;
}
.list-img img {
display: inline-block;
width: 50px;
height:50px;
}
.list-img input {
position: absolute;
top: 0;
left: 0;
z-index: 10;
width: 50px;
height:50px;
opacity: 0;
}
.list-img i {
position: absolute;
top: 0;
right: 0;
width: 15px;
height: 15px;
background: url(../images/icon_del.png) no-repeat center;
background-size: 100%;
}
.list-img .num {
position: absolute;
left: 0;
bottom: 0;
width: 100%;
text-align: center;
color: #999;
font-size: 12px;
}
</style>
</head>
<body>
<div class="list-img">
<ul id="preview" class="clear">
<li class="fl">
<img src="/images/icon_upload.png">
<input id="fileImage" type="file" name="file[]" multiple />
<div class="num">0/4</div>
</li>
</ul>
</div> <script src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
<script>
var pageCtrl = {
imgId : 0, //图片id标志, 方便删除预览图片
maxNum : 4, //最多上传图片张数 /* 选择图片 */
_choosePic : function() {
var _self = this;
$('#fileImage').change(function() {
var files = this.files,
len = $('#preview').find('.pic').length;
if (len + files.length > _self.maxNum) {
_self._showTip('最多只能上传' + _self.maxNum + '张图片哦~');
return;
}
for (var i = 0; i < files.length; i++) {
var file = files[i];
if (file.type.indexOf("image") == 0) {
if (file.size >= 1024 * 1024 * 3) {
_self._showTip('图片大小过大，应小于3M');
} else {
_self._showPic(file); //图片预览
}
} else {
_self._showTip('文件"' + file.name + '"不是图片类型')
break;
}
}
});
}, /* 渲染图片 */
_showPic : function(file) {
var _self = this,
html = '',
$wap = $('#preview'),
reader = new FileReader();
reader.readAsDataURL(file);
reader.onload = function(e) {
var image_base64 = this.result,
imgId = _self.imgId; html = '<li class="fl pic" id="imgItem_' + imgId + '">' +
'<img src="' + image_base64 + '" alt="">' +
'<i class="del-img"></i>' +
'</li>';
imgId++;
$wap.append(html);
$('#fileImage').next().text($wap.find('.pic').length + '/' + _self.maxNum); //图片压缩上传，大于1.2M压缩图片
if (file.size / 1024 > 1024 * 1.2) {
_self._dealImage(image_base64, {
quality: 0.5
}, function(base64Codes) {
var bl = _self._processData(base64Codes, file.type);
_self._uploadPic(bl, imgId);
});
} else {
_self._uploadPic(file, imgId);
}
}
}, /**
* 图片压缩（利用canvas）
* @param path 图片路径
* @param obj 压缩配置width,height,quality，不传则按比例压缩
* @param callback 回调函数
*/
_dealImage : function(path, obj, callback) {
var img = new Image();
img.src = path;
img.onload = function() {
var that = this;
// 默认按比例压缩
var w = that.width,
h = that.height,
scale = w / h;
w = obj.width || w;
h = obj.height || (w / scale); //生成canvas
var canvas = document.createElement('canvas'),
ctx = canvas.getContext('2d');
canvas.width = w;
canvas.height = h;
ctx.drawImage(that, 0, 0, w, h); // 默认图片质量为0.7
var quality = 0.7;
if (obj.quality && obj.quality <= 1 && obj.quality > 0) {
quality = obj.quality;
} // 回调函数返回base64的值
var base64 = canvas.toDataURL('image/jpeg', quality);
callback(base64);
}
}, /* 将以base64的图片url数据转换为Blob */
_processData : function(dataUrl, type) {
var binaryString = window.atob(dataUrl.split(',')[1]),
arrayBuffer = new ArrayBuffer(binaryString.length),
intArray = new Uint8Array(arrayBuffer);
for (var i = 0, j = binaryString.length; i < j; i++) {
intArray[i] = binaryString.charCodeAt(i);
} var data = [intArray], blob; try {
blob = new Blob(data);
} catch (e) {
window.BlobBuilder = window.BlobBuilder ||
window.WebKitBlobBuilder ||
window.MozBlobBuilder ||
window.MSBlobBuilder;
if (e.name === 'TypeError' && window.BlobBuilder) {
var builder = new BlobBuilder();
builder.append(arrayBuffer);
blob = builder.getBlob(type);
} else {
_showTip('版本过低，不支持图片压缩上传');
}
}
return blob;
}, /* 上传图片 */
_uploadPic : function(file, id) {
var _self = this,
formData = new FormData();
formData.append('img', file);
$.ajax({
url: '/upload',
type: 'post',
dataType: 'json',
data: formData,
contentType: false,
processData: false,
success: function(res){
if(res.respCode == 1000) {
$('#imgItem_' + id).find('.del-img').attr('data-src', res.data.src);
}else {
_self._showTip('文件上传失败！');
}
}
});
}, /* 删除图片 */
_delPic : function() {
var _self = this,
$wap = $('#preview');
$wap.on('click', '.del-img', function() {
//TODO:从数据库删除图片
$(this).parent().remove();
$('#fileImage').next().text($wap.find('.pic').length + '/' + _self.maxNum);
});
}, _showTip : function(str) {
//TODO信息提示
console.log(str);
}, init: function() {
this._choosePic();
this._delPic();
}
}; $(function() {
pageCtrl.init();
});
</script>
</body>
</html> 完整代码
完整代码
参考文章：