文本格式调整不过来，代码格式请看
```
image.onload = function() {
// 获取图片旋转角度
var orientation = 1
EXIF.getData(image, function() {
orientation = EXIF.getTag(this, 'Orientation')
})
// alert('orientation-' + orientation)
var width = image.width
var height = image.height
var scale = Math.max(width / options.maxWidth, height / options.maxHeight)
//宽度或高度计算
// if (scale > 1) {
var w = Math.round(width / scale)
var h = Math.round(height / scale)
//生成canvas
var canvas = document.createElement('canvas')
var ctx = (window.ctx = canvas.getContext('2d'))
ctx.save()
switch (orientation) {
case 3: //镜头方向朝右 需要顺时针（向左）180度旋转
console.log('需要顺时针（向左）180度旋转')
canvas.width = h
canvas.height = w
ctx.translate(canvas.width / 2, canvas.height / 2)
ctx.rotate((180 * Math.PI) / 180)
ctx.drawImage(this, -w / 2, -h / 2, w, h)
break
case 6: //镜头正拍 需要顺时针（向右）90度旋转
console.log('需要顺时针（向左）90度旋转')
canvas.width = h
canvas.height = w
ctx.translate(canvas.width / 2, canvas.height / 2)
ctx.rotate((90 * Math.PI) / 180)
ctx.drawImage(this, -w / 2, -h / 2, w, h)
break
case 8: //镜头朝下 需要逆时针（向左）90度旋转"
console.log('需要逆时针（向右）90度旋转')
canvas.width = h
canvas.height = w
ctx.translate(canvas.width / 2, canvas.height / 2)
ctx.rotate((-90 * Math.PI) / 180)
ctx.drawImage(this, -w / 2, -h / 2, w, h)
break
default:
//有的机型无论是什么方向统一返回 0 1 //镜头方向朝左
canvas.width = w
canvas.height = h
ctx.drawImage(this, 0, 0, w, h)
break
}
ctx.restore()
imageData = canvas.toDataURL('image/jpeg', 0.8)
// }
callback && callback(imageData, 0)
}
```
