【移动应用开发技术】Android中怎么实现动态人脸检测

【移动应用开发技术】Android中怎么实现动态人脸检测

Android中怎么实现动态人脸检测，针对这个问题，这篇文章详细介绍了相对应的分析和解答，希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。第一步我们首先来定义一个surfaceview盖在我们Carmen使用的surfaceview上进行对人脸范围的绘制public

class

FindFaceView

extends

SurfaceView

implements

SurfaceHolder.Callback

{

private

SurfaceHolder

holder;

private

int

mWidth;

private

int

mHeight;

private

float

eyesDistance;

public

FindFaceView(Context

context,

AttributeSet

attrs)

{

super(context,

attrs);

holder

=

getHolder();

holder.addCallback(this);

holder.setFormat(PixelFormat.TRANSPARENT);

this.setZOrderOnTop(true);

}

@Override

public

void

surfaceChanged(SurfaceHolder

holder,

int

format,

int

width,

int

height)

{

mWidth

=

width;

mHeight

=

height;

}

@Override

public

void

surfaceCreated(SurfaceHolder

holder)

{

}

@Override

public

void

surfaceDestroyed(SurfaceHolder

holder)

{

}

public

void

drawRect(FaceDetector.Face[]

faces,

int

numberOfFaceDetected)

{

Canvas

canvas

=

holder.lockCanvas();

if

(canvas

!=

null)

{

Paint

clipPaint

=

new

Paint();

clipPaint.setAntiAlias(true);

clipPaint.setStyle(Paint.Style.STROKE);

clipPaint

.setXfermode(new

PorterDuffXfermode(PorterDuff.Mode.CLEAR));

canvas.drawPaint(clipPaint);

canvas.drawColor(getResources().getColor(color.transparent));

Paint

paint

=

new

Paint();

paint.setAntiAlias(true);

paint.setColor(Color.GREEN);

paint.setStyle(Style.STROKE);

paint.setStrokeWidth(5.0f);

for

(int

i

=

0;

i

<

numberOfFaceDetected;

i++)

{

Face

face

=

faces[i];

PointF

midPoint

=

new

PointF();

//

获得两眼之间的中间点

face.getMidPoint(midPoint);

//

获得两眼之间的距离

eyesDistance

=

face.eyesDistance();

//

换算出预览图片和屏幕显示区域的比例参数

float

scale_x

=

mWidth

/

500;

float

scale_y

=

mHeight

/

600;

Log.e("eyesDistance=",

eyesDistance

+

"");

Log.e("midPoint.x=",

midPoint.x

+

"");

Log.e("midPoint.y=",

midPoint.y

+

"");

//

因为拍摄的相片跟实际显示的图像是镜像关系，所以在图片上获取的两眼中间点跟手机上显示的是相反方向

canvas.drawRect((int)

(240

-

midPoint.x

-

eyesDistance)

*

scale_x,

(int)

(midPoint.y

*

scale_y),

(int)

(240

-

midPoint.x

+

eyesDistance)

*

scale_x,

(int)

(midPoint.y

+

3

*

eyesDistance)

*

scale_y,

paint);

}

holder.unlockCanvasAndPost(canvas);

}

}

}重要的地方1.holder=getHolder();获取surfaceholder与我们要绘制人脸范围的画布进行绑定Canvascanvas=holder.lockCanvas();这样我们就可以愉快的进行绘制了，当然前提是我们要拿到人脸的坐标位置。2.还有重要的一点，就是要让我们用来盖在Carema上的Surfaceview可以同名，并且设置起在视图树的层级为最高。

holder.setFormat(PixelFormat.TRANSPARENT);

this.setZOrderOnTop(true);第二步就是我们对人脸进行检测了，当然前提是我们要获得帧图public

class

FaceRecognitionDemoActivity

extends

Activity

implements

OnClickListener

{

private

SurfaceView

preview;

private

Camera

camera;

private

Camera.Parameters

parameters;

private

int

orientionOfCamera;//

前置摄像头的安装角度

private

int

faceNumber;//

识别的人脸数

private

FaceDetector.Face[]

faces;

private

FindFaceView

mFindFaceView;

private

ImageView

iv_photo;

private

Button

bt_camera;

TextView

mTV;

/**

*

Called

when

the

activity

is

first

created.

*/

@Override

public

void

onCreate(Bundle

savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

}

@Override

protected

void

onStart()

{

super.onStart();

iv_photo

=

(ImageView)

findViewById(R.id.iv_photo);

bt_camera

=

(Button)

findViewById(R.id.bt_camera);

mTV

=

(TextView)

findViewById(R.id.show_count);

bt_camera.setOnClickListener(this);

mFindFaceView

=

(FindFaceView)

findViewById(R.id.my_preview);

preview

=

(SurfaceView)

findViewById(R.id.preview);

//

设置缓冲类型（必不可少）

preview.getHolder().setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

//

设置surface的分辨率

preview.getHolder().setFixedSize(176,

144);

//

设置屏幕常亮（必不可少）

preview.getHolder().setKeepScreenOn(true);

preview.getHolder().addCallback(new

SurfaceCallback());

}

private

final

class

MyPictureCallback

implements

PictureCallback

{

@Override

public

void

onPictureTaken(byte[]

data,

Camera

camera)

{

try

{

Bitmap

bitmap

=

BitmapFactory.decodeByteArray(data,

0,

data.length);

Matrix

matrix

=

new

Matrix();

matrix.setRotate(-90);

Bitmap

bmp

=

Bitmap.createBitmap(bitmap,

0,

0,

bitmap

.getWidth(),

bitmap.getHeight(),

matrix,

true);

bitmap.recycle();

iv_photo.setImageBitmap(bmp);

camera.startPreview();

}

catch

(Exception

e)

{

e.printStackTrace();

}

}

}

private

final

class

SurfaceCallback

implements

Callback

{

@Override

public

void

surfaceChanged(SurfaceHolder

holder,

int

format,

int

width,

int

height)

{

if

(camera

!=

null)

{

parameters

=

camera.getParameters();

parameters.setPictureFormat(PixelFormat.JPEG);

//

设置预览区域的大小

parameters.setPreviewSize(width,

height);

//

设置每秒钟预览帧数

parameters.setPreviewFrameRate(20);

//

设置预览图片的大小

parameters.setPictureSize(width,

height);

parameters.setJpegQuality(80);

}

}

@Override

public

void

surfaceCreated(SurfaceHolder

holder)

{

int

cameraCount

=

0;

Camera.CameraInfo

cameraInfo

=

new

Camera.CameraInfo();

cameraCount

=

Camera.getNumberOfCameras();

//设置相机的参数

for

(int

i

=

0;

i

<

cameraCount;

i++)

{

Camera.getCameraInfo(i,

cameraInfo);

if

(cameraInfo.facing

==

Camera.CameraInfo.CAMERA_FACING_FRONT)

{

try

{

camera

=

Camera.open(i);

camera.setPreviewDisplay(holder);

setCameraDisplayOrientation(i,

camera);

//最重要的设置

帧图的回调

camera.setPreviewCallback(new

MyPreviewCallback());

camera.startPreview();

}

catch

(Exception

e)

{

e.printStackTrace();

}

}

}

}

@Override

public

void

surfaceDestroyed(SurfaceHolder

holder)

{

//记得释放，避免OOM和占用

if

(camera

!=

null)

{

camera.setPreviewCallback(null);

camera.stopPreview();

camera.release();

camera

=

null;

}

}

}

private

class

MyPreviewCallback

implements

PreviewCallback

{

@Override

public

void

onPreviewFrame(byte[]

data,

Camera

camera)

{

//这里需要注意，回调出来的data不是我们直接意义上的RGB图

而是YUV图，因此我们需要

//将YUV转化为bitmap再进行相应的人脸检测，同时注意必须使用RGB_565，才能进行人脸检测，其余无效

Camera.Size

size

=

camera.getParameters().getPreviewSize();

YuvImage

yuvImage

=

new

YuvImage(data,

ImageFormat.NV21,

size.width,

size.height,

null);

ByteArrayOutputStream

baos

=

new

ByteArrayOutputStream();

yuvIpressToJpeg(new

Rect(0,

0,

size.width,

size.height),

80,

baos);

byte[]

byteArray

=

baos.toByteArray();

detectionFaces(byteArray);

}

}

/**

*

检测人脸

*

*

@param

data

预览的图像数据

*/

private

void

detectionFaces(byte[]

data)

{

BitmapFactory.Options

options

=

new

BitmapFactory.Options();

Bitmap

bitmap1

=

BitmapFactory.decodeByteArray(data,

0,

data.length,

options);

int

width

=

bitmap1.getWidth();

int

height

=

bitmap1.getHeight();

Matrix

matrix

=

new

Matrix();

Bitmap

bitmap2

=

null;

FaceDetector

detector

=

null;

//设置各个角度的相机，这样我们的检测效果才是最好

switch

(orientionOfCamera)

{

case

0:

//初始化人脸检测（下同）

detector

=

new

FaceDetector(width,

height,

10);

matrix.postRotate(0.0f,

width

/

2,

height

/

2);

//

以指定的宽度和高度创建一张可变的bitmap（图片格式必须是RGB_565，不然检测不到人脸）

bitmap2

=

Bitmap.createBitmap(width,

height,

Bitmap.Config.RGB_565);

break;

case

90:

detector

=

new

FaceDetector(height,

width,

1);

matrix.postRotate(-270.0f,

height

/

2,

width

/

2);

bitmap2

=

Bitmap.createBitmap(height,

width,

Bitmap.Config.RGB_565);

break;

case

180:

detector

=

new

FaceDetector(width,

height,

1);

matrix.postRotate(-180.0f,

width

/

2,

height

/

2);

bitmap2

=

Bitmap.createBitmap(width,

height,

Bitmap.Config.RGB_565);

break;

case

270:

detector

=

new

FaceDetector(height,

width,

1);

matrix.postRotate(-90.0f,

height

/

2,

width

/

2);

bitmap2

=

Bitmap.createBitmap(height,

width,

Bitmap.Config.RGB_565);

break;

}

//设置支持的面数（最大支持检测多少人的脸

，可以根据需要调整，不过需要与findFaces中的参数数值相同，否则会抛出异常）

faces

=

new

FaceDetector.Face[10];

Paint

paint

=

new

Paint();

paint.setDither(true);

Canvas

canvas

=

new

Canvas();

canvas.setBitmap(bitmap2);

canvas.setMatrix(matrix);

//

将bitmap1画到bitmap2上（这里的偏移参数根据实际情况可能要修改）

canvas.drawBitmap(bitmap1,

0,

0,

paint);

//这里通过向findFaces中传递帧图转化后的bitmap和最大检测的人脸数face，返回检测后的人脸数

faceNumber

=

detector.findFaces(bitmap2,

faces);

mTV.setText("facnumber"

+

faceNumber);

mTV.setTextColor(Color.RED);

//这里就是我们的人脸识别，绘制识别后的人脸区域的类

if

(faceNumber

!=

0)

{

mFindFaceView.setVisibility(View.VISIBLE);

mFindFaceView.drawRect(faces,

faceNumber);

}

else

{

mFindFaceView.setVisibility(View.GONE);

}

bitmap2.recycle();

bitmap1.recycle();

}

/**

*

设置相机的显示方向（这里必须这么设置，不然检测不到人脸）

*

*

@param

cameraId

相机ID(0是后置摄像头，1是前置摄像头）

*

@param

camera

相机对象

*/

private

void

setCameraDisplayOrientation(int

cameraId,

Camera

camera)

{

Camera.CameraInfo

info

=

new

Camera.CameraInfo();

Camera.getCameraInfo(cameraId,

info);

int

r