效果图：

第一种是使用camerax进行预览，android camerax预览官方文档，主要通过imageAnalysis，抓帧进行图片处理，然后通过android自带的图片人脸识别FaceDetector判断是否有人脸，有人脸保存当前抓拍的照片：

val file = File(filesDir, "head_tmp.png")

val create = Observable.create { emitter ->

val intArray = IntArray(2)

iv_scan.getLocationInWindow(intArray)

val createBitmap = Bitmap.createBitmap(

bitmap, intArray[0], intArray[1], iv_scan.width, iv_scan.height

)

//必须是565才能识别

val bitmap1: Bitmap = createBitmap.copy(Bitmap.Config.RGB_565, true)

val faceDetector = FaceDetector(bitmap1.width, bitmap1.height, 1)

val array = arrayOfNulls(1)

val faces = faceDetector.findFaces(bitmap1, array)

if (faces > 0) {

Log.e(TAG, "检测到脸")

val fos = FileOutputStream(file.path)

createBitmap.compress(Bitmap.CompressFormat.PNG, 100, fos)

fos.flush()

fos.close()

emitter.onNext(file)

} else {

Log.e(TAG, "未检测到脸")

emitter.onError(Throwable("未检测到脸"))

}

}

var disposable: Disposable? = null

val observer = object : Observer {

override fun onNext(t: File) {

disposable?.dispose()

isOne = false

setResult(Activity.RESULT_OK)

finish()

}

override fun onError(e: Throwable) {

isOne = true

}

override fun onComplete() {

}

override fun onSubscribe(d: Disposable) {

disposable = d

}

}

create.subscribeOn(Schedulers.computation())//指定被观察者线程

.observeOn(AndroidSchedulers.mainThread())//指定观察者线程

.subscribe(observer)

第二种使用了免费的虹软识别人脸识别，主要判断指定识别框的rect和虹软人脸识别框的rect,比较两个rect，是否在它的范围内，如果在抓拍人脸：

if (drawInfoList.size > 0) {

for (i in drawInfoList.indices) {

val rect: Rect = drawInfoList[i].rect

val rect1 = Rect()

iv_scan.getGlobalVisibleRect(rect1)

if (rect1.contains(rect)) {

//为了美观，扩大rect截取注册图

val cropRect: Rect =

CommUtils.getBestRect(

previewSize!!.width, previewSize!!.height, faceInfoList[i].rect

)

cropRect.left = cropRect.left and 3.inv()

cropRect.top = cropRect.top and 3.inv()

cropRect.right = cropRect.right and 3.inv()

cropRect.bottom = cropRect.bottom and 3.inv()

headBmp = CommUtils.getHeadImage(

nv21,

previewSize!!.width,

previewSize!!.height,

faceInfoList[i].orient,

cropRect,

ArcSoftImageFormat.NV21

)

headBmp?.apply {

cropBitmap(this)

}

break

}

}

}

demo：https://github.com/withyi9223/facesb