微信小程序开发文档：https://developers./miniprogram/dev/component/camera.html
首先，需要用户授权摄像头权限，这一步是必须的
具体步骤：
获取用户当前授权状态，看是否已经授权，如果已经授权直接显示摄像头如果用户还没有授权，则调起授权弹框，用户允许授权则显示摄像头如果用户不允许，则提示用户去设置页面打开摄像头权限
用户授权之后，就可以进行拍摄了，微信的camera组件无法显示为圆形，我这里是用一张图片遮盖了
上代码：
wxml：
<view class='camera'><image src="/images/border.png" mode="widthFix"></image><camera wx:if="{{isAuth}}" device-position="back" flash="off" binderror="error"></camera></view><button class="takePhoto" type="primary" bindtap="takePhoto">拍照</button>
wxss:
.camera {width: 430rpx;height: 430rpx;border-radius: 50%;margin: 20px auto 0;position: relative;}.camera image {position: absolute;width: 100%;height: 100%;z-index: 10;}.camera camera {width: 428rpx;height: 428rpx;}button.takePhoto:not([size='mini']) {position: fixed;bottom: 0;left: 0;width: 100vw;height: 90rpx;border-radius: 0;}
js:
Page({data: {isAuth: false,src: ''},onLoad() {const _this = thiswx.getSetting({success: res => {if (res.authSetting['scope.camera']) {// 用户已经授权_this.setData({isAuth: true})} else {// 用户还没有授权，向用户发起授权请求wx.authorize({scope: 'scope.camera',success() { // 用户同意授权_this.setData({isAuth: true})},fail() { // 用户不同意授权_this.openSetting().then(res => {_this.setData({isAuth: true})})}})}},fail: res => {console.log('获取用户授权信息失败')}})},// 打开授权设置界面openSetting() {const _this = thislet promise = new Promise((resolve, reject) => {wx.showModal({title: '授权',content: '请先授权获取摄像头权限',success(res) {if (res.confirm) {wx.openSetting({success(res) {if (res.authSetting['scope.camera']) { // 用户打开了授权开关resolve(true)} else { // 用户没有打开授权开关， 继续打开设置页面_this.openSetting().then(res => {resolve(true)})}},fail(res) {console.log(res)}})} else if (res.cancel) {_this.openSetting().then(res => {resolve(true)})}}})})return promise;},takePhoto() {const ctx = wx.createCameraContext()ctx.takePhoto({quality: 'high',success: (res) => {this.setData({src: res.tempImagePath})wx.previewImage({current: res.tempImagePath, // 当前显示图片的http链接urls: [res.tempImagePath] // 需要预览的图片http链接列表})}})}})
