1. 效果
演示地址：https://www.albertyy.com/2020/8/rotateImg.html
2. canvas
关于canvas的使用我在这篇文章 https://blog.csdn.net/qq_23853743/article/details/107434946 中有简单的介绍，可以看一下。
3. 代码实现
<!DOCTYPE html>
<html>
<head>
<title>图片旋转：公众号AlbertYang</title>
</head>
<style type="text/css">
#content {
800px;
height: auto;
margin: auto;
}
img {
100%;
}
input {
150px;
height: 30px;
}
button {
60px;
height: 30px;
cursor: pointer;
}
.canvasbox canvas {
100%
}
</style>
<body>
<div id="content">
<div class="imgbox"><img id="img" src="./img/image_20200813.jpg"></div>
<div>
<input type="number" id="number" name="" placeholder="输入旋转角度">
<button onclick="drawImg()">draw</button>
</div>
<div class="canvasbox" width="800px">
<img id="testimg" />
</div>
</div>
</body>
<script type="text/javascript">
function drawImgToCanvas(image, rotate) {
var testImg = document.getElementById('testimg')
var canvas = document.createElement("canvas");
var context = canvas.getContext('2d')
var img = new Image();
console.log(60);
img.setAttribute('crossOrigin', 'Anonymous')
img.src = image.src;
img.onload = function() {
canvas.width = img.height;
canvas.height = img.width;
context.translate(canvas.width / 2, canvas.height / 2)
context.rotate(rotate * Math.PI / 180)
context.translate(-canvas.width / 2, -canvas.height / 2)
context.drawImage(img, canvas.width / 2 - img.width / 2, canvas.height / 2 - img.height / 2)
context.translate(canvas.width / 2, canvas.height / 2)
context.rotate(-rotate * Math.PI / 180)
context.translate(-canvas.width / 2, -canvas.height / 2)
context.restore()
var base64 = canvas.toDataURL("image/jpeg", 0.9);
testImg.src = base64;
console.log('base64', base64);
};
}
function drawImg() {
var image = document.getElementById('img');
var rotate = document.getElementById('number').value * 1;
drawImgToCanvas(image, rotate);
}
</script>
</html>