JS实现图片旋转的两种方案：CSS与Canvas对比及注意事项

<template>
  <div style="width: 100%; height: 100%">
    <img class="img-item" src="https://img2.baidu.com/it/u=1906732828,3160455141&fm=253&fmt=auto&app=138&f=JPEG?w=500&h=666" />
    <img class="img-item" src="https://img0.baidu.com/it/u=2911164322,2998857390&fm=253&fmt=auto&app=138&f=JPEG?w=346&h=500" />
  </div>
</template>
<script>
export default {
  name: "deviceAssets",
  data() {
    return {}
  },
  mounted() {
    this.initPage()
  },
  methods: {
    initPage() {
      this.$nextTick(async() => {
        let imgList = document.getElementsByClassName("img-item")
        if (!imgList) return
        for(let i=0; i < imgList.length; i++) {
          this.rotateBase64Img(imgList[i].src, 90, (url) => {
            console.log(`imgList[${i}].src`, url)
            imgList[i].src = url
          })
        }
      })
    },
    // 传入图片src，旋转图片后，返回一个图片信息对象
    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 () {
        console.log('加载了');
        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);
        //drawImage向画布上绘制图片
        ctx?.drawImage(image, 0, 0);
        //getImageData() 复制画布上指定矩形的像素数据
        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;
        }
        //putImageData() 将图像数据放回画布
        ctx?.putImageData(imgData, 0, 0);
        callback(canvas.toDataURL('image/png'));  
      };
    }
  }
}
</script>
<style lang="scss" scoped>
.iframe {
  width: 98%;
  height: 98%;
  box-sizing: border-box;
}
.img-box {
  width: 700px;
  height: 700px;
  background-color: #ccc;
  .img {
    width: 100%;
    transform: rotateZ(90deg) ;
  }
}
</style>