解决layui上传图片预览旋转90度的问题

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我是靠谱客的博主殷勤大侠，最近开发中收集的这篇文章主要介绍解决layui上传图片预览旋转90度的问题，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

问题：使用layui上传图片的，出现图片旋转90度

解决办法：通过EXIF.getData获取图片信息，判断图片是否旋转

html:

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<link rel="stylesheet" href="../layui/css/layui.css"
media="all">
<link rel="stylesheet" href="../css/showImg.css">
</head>
<body>
<div class="layui-upload">
<button class="layui-btn" id="test1" type="button">上传图片</button>
<div class="layui-upload-list">
<img class="layui-upload-img" id="demo1">
<p id="demoText"></p>
</div>
</div>
<script src="../layui/layui.js" charset="utf-8"></script>
<script src="../js/showImg.js"></script>
<script type="text/javascript" src="../js/exif.js"></script>
</body>
</html>

js:

layui.use('upload', function() {
var $ = layui.jquery
, upload = layui.upload;
//普通图片上传
var uploadInst = upload.render({
elem: '#test1'
, url: '/upload/'
, before: function (obj) {
//预读本地文件示例，不支持ie8
obj.preview(function (index, file, result) {
console.log(file)
EXIF.getData(file, function() {
//获取图片Orientation
orient = EXIF.getTag(this, 'Orientation');
if(orient==6){//逆时针旋转了90度
rotateBase64Img(result,90,callback);
}else if(orient==1){
$('#demo1').attr('src', result); //图片链接（base64）
}
});
});
}
, done: function (res) {
//如果上传失败
if (res.code > 0) {
return layer.msg('上传失败');
}
//上传成功
}
, error: function () {
//演示失败状态，并实现重传
var demoText = $('#demoText');
demoText.html('<span style="color: #FF5722;">上传失败</span> <a class="layui-btn layui-btn-xs demo-reload">重试</a>');
demoText.find('.demo-reload').on('click', function () {
uploadInst.upload();
});
}
});
//旋转base64图片
function rotateBase64Img(src, edg, callback) {
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
var imgW;//图片宽度
var imgH;//图片高度
var size;//canvas初始大小
if (edg % 90 != 0) {
console.error("旋转角度必须是90的倍数!");
throw '旋转角度必须是90的倍数!';
}
(edg < 0) && (edg = (edg % 360) + 360)
const quadrant = (edg / 90) % 4; //旋转象限
const cutCoor = {sx: 0, sy: 0, ex: 0, ey: 0}; //裁剪坐标
var image = new Image();
image.crossOrigin = "anonymous"
image.src = src;
image.onload = function () {
imgW = image.width;
imgH = image.height;
size = imgW > imgH ? imgW : imgH;
canvas.width = size * 2;
canvas.height = size * 2;
switch (quadrant) {
case 0:
cutCoor.sx = size;
cutCoor.sy = size;
cutCoor.ex = size + imgW;
cutCoor.ey = size + imgH;
break;
case 1:
cutCoor.sx = size - imgH;
cutCoor.sy = size;
cutCoor.ex = size;
cutCoor.ey = size + imgW;
break;
case 2:
cutCoor.sx = size - imgW;
cutCoor.sy = size - imgH;
cutCoor.ex = size;
cutCoor.ey = size;
break;
case 3:
cutCoor.sx = size;
cutCoor.sy = size - imgW;
cutCoor.ex = size + imgH;
cutCoor.ey = size + imgW;
break;
}
ctx.translate(size, size);
ctx.rotate(edg * Math.PI / 180);
ctx.drawImage(image, 0, 0);
var imgData = ctx.getImageData(cutCoor.sx, cutCoor.sy, cutCoor.ex, cutCoor.ey);
if (quadrant % 2 == 0) {
canvas.width = imgW;
canvas.height = imgH;
} else {
canvas.width = imgH;
canvas.height = imgW;
}
ctx.putImageData(imgData, 0, 0);
callback(canvas.toDataURL())
};
}
function callback(base64data) {
document.getElementById("demo1").src = base64data;
}
});