vue 图片压缩
上传图片大于100* 1024 的用canvas 来压缩来解决
然后IOS拍照上传会有图片旋转的问题，然后用了github 上的exif.js很好的插件，项目里面npm install exif-js --save 安装，
然后import一下就可以使用了，来看看代码吧
HTML+CSS+JS Vue的组件代码
import Exif from'exif-js'
export default {
data () {
return {
headerImage:'',picValue:'' }
},
mounted () {
},
methods: {
upload (e) {
let files = e.target.files || e.dataTransfer.files;
if(!files.length)return;
this.picValue = files[0];
this.imgPreview(this.picValue);
},
imgPreview (file) {
let self =this;
let Orientation;
//去获取拍照时的信息，解决拍出来的照片旋转问题 Exif.getData(file, function(){
Orientation = Exif.getTag(this,'Orientation');
});
// 看支持不支持FileReaderif(!file || !window.FileReader)return;
if(/^image/.test(file.type)) {
// 创建一个readerlet reader =new FileReader();
// 将图片2将转成 base64 格式 reader.readAsDataURL(file);
// 读取成功后的回调reader.onloadend = function () {
let result =this.result;
let img =new Image();
img.src = result;
//判断图片是否大于100K,是就直接上传，反之压缩图片if(this.result.length <= (100*1024)) {
self.headerImage =this.result;
self.postImg();
}else {
img.onload = function () {
let data = self.compress(img,Orientation);
self.headerImage = data;
self.postImg();
}
}
}
}
},
postImg () {
//这里写接口 },
rotateImg (img, direction,canvas) {
//最小与最大旋转方向，图片旋转4次后回到原方向 constmin_step =0;
constmax_step =3;
if(img ==null)return;
//img的高度和宽度不能在img元素隐藏后获取，否则会出错 let height = img.height;
let width = img.width;
let step =2;
if(step ==null) {
step = min_step;
}
if(direction =='right') {
step++;
//旋转到原位置，即超过最大值 step > max_step && (step = min_step);
} else {
step--;
step < min_step && (step = max_step);
}
//旋转角度以弧度值为参数 let degree = step *90* Math.PI /180;
let ctx = canvas.getContext('2d');
switch (step) {
case0:
canvas.width = width;
canvas.height = height;
ctx.drawImage(img, 0,0);
break;
case1:
canvas.width = height;
canvas.height = width;
ctx.rotate(degree);
ctx.drawImage(img, 0, -height);
break;
case2:
canvas.width = width;
canvas.height = height;
ctx.rotate(degree);
ctx.drawImage(img, -width, -height);
break;
case3:
canvas.width = height;
canvas.height = width;
ctx.rotate(degree);
ctx.drawImage(img, -width,0);
break;
}
},
compress(img,Orientation) {
let canvas = document.createElement("canvas");
let ctx = canvas.getContext('2d');
//瓦片canvaslet tCanvas = document.createElement("canvas");
let tctx = tCanvas.getContext("2d");
let initSize = img.src.length;
let width = img.width;
let 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 let ratio;
if((ratio = width * height /4000000) >1) {
console.log("大于400万像素")
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 let count;
if((count = width * height /1000000) >1) {
console.log("超过100W像素");
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let nw = ~~(width / count);
let nh = ~~(height / count);
tCanvas.width = nw;
tCanvas.height = nh;
for(let i =0; i < count; i++) {
for(let 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);
}
//修复ios上传图片的时候 被旋转的问题if(Orientation !=""&& Orientation !=1){
switch(Orientation){
case6://需要顺时针（向左）90度旋转this.rotateImg(img,'left',canvas);
break;
case8://需要逆时针（向右）90度旋转this.rotateImg(img,'right',canvas);
break;
case3://需要180度旋转this.rotateImg(img,'right',canvas);//转两次this.rotateImg(img,'right',canvas);
break;
}
}
//进行最小压缩let 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;
},
}
} *{
margin: 0;
padding: 0;
}
.show {
width: 100px;
height: 100px;
overflow: hidden;
position: relative;
border-radius:50%;
border: 1px solid #d5d5d5;
}
.picture {
width: 100%;
height: 100%;
overflow: hidden;
background-position: center center;
background-repeat: no-repeat;
background-size: cover;
}
···
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