需求
混合App开发,原生壳子+webApp,在web部分调用原生摄像头功能并且在网页指定区域显示摄像头内容,同时可以手动拍照并进行人脸识别,将识别结果显示在网页上。
技术栈
vue、Html5、video标签、Android、IOS、百度AI
分析
1、使用navigator.mediaDevices.getUserMedia调用系统原生摄像头功能
2、video标签显示摄像头内容
3、canvas标签获取图片
4、将图像上传服务器,通过百度AI识别图片
5、web显示识别结果
核心代码
1、调用系统原生摄像头功能并使用video标签显示html:
<video
id="webcam"
style="videoStyle"
width="videoWidth"
height="videoHeight"
loop
preload
>
</video>
JavaScript:
initVideo() {
let that = this;
this.video = document.getElementById("webcam");
setTimeout(() => {
if (
navigator.mediaDevices.getUserMedia ||
navigator.getUserMedia ||
navigator.webkitGetUserMedia ||
navigator.mozGetUserMedia
) {
//调用用户媒体设备, 访问摄像头
this.getUserMedia(
{
video: {
width: {
ideal: that.videoWidth,
max: that.videoWidth
},
height: {
ideal: that.videoHeight,
max: that.videoHeight
},
facingMode: "user", //前置摄像头
frameRate: {
ideal: 30,
min: 10
}
}
},
this.videoSuccess,
this.videoError
);
} else {
this.$toast.center("摄像头打开失败,请检查权限设置!");
}
}, 300);
},
getUserMedia(constraints, success, error) {
if (navigator.mediaDevices.getUserMedia) {
//最新的标准API
navigator.mediaDevices
.getUserMedia(constraints)
.then(success)
.catch(error);
} else if (navigator.webkitGetUserMedia) {
//webkit核心浏览器
navigator.webkitGetUserMedia(constraints, success, error);
} else if (navigator.mozGetUserMedia) {
//firfox浏览器
navigator.mozGetUserMedia(constraints, success, error);
} else if (navigator.getUserMedia) {
//旧版API
navigator.getUserMedia(constraints, success, error);
}
}
videoSuccess(stream) {
this.mediaStreamTrack = stream;
this.video.srcObject = stream;
this.video.play();
},
videoError(error) {
console.error(error);
this.$toast.center("摄像头打开失败,请检查权限设置!");
},
2、canvas获取摄像头图片
JavaScript:
this.canvas = document.createElement("canvas");
....
let context = this.canvas.getContext("2d");
context.drawImage(this.video, 0, 0, this.videoWidth, this.videoHeight);
this.imgSrc = this.canvas.toDataURL("image/png");
3、调用百度AI识别图片
JavaScript:
let that = this;
let base64Data = this.canvas.toDataURL();
let blob = this.dataURItoBlob(base64Data);
var file = new FormData();
file.append("file", blob);
file.append("key", that.uuid);
util.ajax
.post("XXXXXXXXXX", file, {
headers: {
"Content-Type": "multipart/form-data"
}
})
.then(function(response) {
if ((response.status = 200)) {
.....识别成功,显示结果
} else {
......识别失败
}
})
.catch(function(error) {
console.error(error);
});
//base64转换为Blob
dataURItoBlob(base64Data) {
var byteString;
if (base64Data.split(",")[0].indexOf("base64") >= 0)
byteString = atob(base64Data.split(",")[1]);
else byteString = unescape(base64Data.split(",")[1]);
var mimeString = base64Data
.split(",")[0]
.split(":")[1]
.split(";")[0];
var ia = new Uint8Array(byteString.length);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
return new Blob([ia], { type: mimeString });
},
手机适配
1、由于Android6之后,Android的权限管理出现变化,Android原生的壳子,需要做如下处理:
myWebView.setWebChromeClient(new WebChromeClient() {
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
@Override
public void onPermissionRequest(final PermissionRequest request) {
request.grant(request.getResources());
}
});
2、IOS系统,Safari11之后可用
3、OverconstrainedError错误,部分Android手机会报OverconstrainedError错误,原因是摄像头参数设置不合理,找不到指定设置。