有的人会遇到需要在前端代码处理图片压缩的问题，下面给大家分享怎么处理。
// 上传图片
var image_src
var IsImgDeal=false;
layui.upload.render({
elem: "#{tag}{id}",
url: sessionStorage.getItem('httpUrlPrefix') + '/upload/uploadImage',
// dataType: 'text',
// auto: false,
// multiple: true,
accept:"images",
exts: 'jpg|png|jpeg',
acceptMime:"image/jpeg,image/png",
before: function (obj) {
layer.msg("图片上传中...", { icon: 16, shade: 0.01 })
},
done: function(res){
layer.msg(`<div style="display:flex;"><div class="tipsSuccess"></div>
<div class="titleTips">提示
</div>
</div>
<div class="context" ><br>上传成功！</div>`
, {
skin: 'success-class',
time: 1000
});
layer.closeAll('loading'); //关闭loading
console.log("sfafasfa",JSON.stringify(res))
image_src = res.url
IsImgDeal = false;
},
choose: function (obj) {
obj.preview(function (index, file, result) {
console.log("================>",file)
let filename = file.name
// console.log("================>",result)
//临时存储二进制流
$("#uploadnewImg-{id}").hide()
$("#uploadexistimg-{id}").show()
$("#uploadImg-{id}").attr("src", result);
});
if (IsImgDeal) {
return;//图片处理过就直接上传
}
console.log("图片压缩开始处理");
var files = obj.pushFile();
var file_tar = null,index_tar = null;
for (var k in files) {
index_tar = k;
file_tar = files[k];
break;
}
//进行图片压缩，直接百度压缩方法
let reader = new FileReader();
var filename = file_tar.name;
reader.readAsDataURL(file_tar);
reader.onload = function () {
let content = this.result; //图片的src，base64格式
let img = new Image();
img.src = content;
img.onload = function () { //图片加载完毕
let canvas = document.createElement("canvas");
let ctx = canvas.getContext('2d');
let width = Math.ceil(img.width*0.8);
let height = Math.ceil(img.height*0.8);
canvas.width = width;
canvas.height = height;
ctx.drawImage(img, 0, 0, width, height);//压缩图片尺寸
let dataURL = canvas.toDataURL("image/jpeg");//如果是需要质量压缩就补充参数
//将base64数据转化为文件对象
var arr = dataURL.split(','), mime = arr[0].match(/:(.*?);/)[1],
bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);
while (n--) {
u8arr[n] = bstr.charCodeAt(n);
}
IsImgDeal = true;//设置标记
//如果有时差问题，后面setTimeout延时再执行，让原来的上传终止
obj.upload(index_tar, new File([new Blob([u8arr], { type: mime })], filename));//单独上传
//uploadIns.upload();//重新启动全部文件上传
}
};
layer.load(); //上传loading
//停止原本的上传，如果多个文件，需要在读取完毕后将files里面的文件队列全删除。
return delete files[index_tar];
},
});