1. Add Camera
a. Add permission line in file "AndroidManifest.xml":
<uses-permission android:name="android.permission.CAMERA" />
b. Subclass SurfaceView: MyView:
public class MyView extends SurfaceView{
Bitmap bmp2Display;
public MyView(Context context, AttributeSet attrs) {
super(context, attrs);
}
Paint paint = new Paint();
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawText("time = "+System.currentTimeMillis(), 50, 100, paint);
}
}
c. Add an instance of MyView in "activity_mail.xml":
<org.ski.helloworld.MyView
android:id="@+id/myView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true" />
d. Add "implements SurfaceHolder.Callback" in MainActivity, and added unimplemented functions as hinted
public class MainActivity extends Activity implements SurfaceHolder.Callback{
//...
// ...
}
e. Add MyView, Camera, its callback and image size:
MyView myView;
int width = 960, height=720;
Camera mCamera;
Camera.PreviewCallback cbWithBuffer;
f. Define callback function:
Camera.PreviewCallback cabWithBuffer = new Camera.PreviewCallback() {
public void onPreviewFrame(byte[] _data, Camera _camera) {
// do something
_camera.addCallbackBuffer(_data);
}
};
g. Add implementations for SurfaceHolder.Callback
@Override
public void surfaceCreated(SurfaceHolder holder) {
mCamera = Camera.open();
mCamera.addCallbackBuffer(new byte[width * height * 2]); // YUV
mCamera.setPreviewCallbackWithBuffer(cabWithBuffer);
try {
mCamera.setPreviewDisplay(holder);
} catch (IOException exception) {
mCamera.release();
mCamera = null;
}
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(width, height);
mCamera.setParameters(parameters);
mCamera.setPreviewCallbackWithBuffer(cbWithBuffer);
mCamera.startPreview();
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
mCamera.stopPreview();
mCamera.setPreviewCallbackWithBuffer(null);
mCamera.release();
mCamera = null;
}
2. Process video:
a. Declare matrices:
Mat mYuv, mRgba;
b. Allocate space for mYuv, mRgb in createOpencvMatrices():
mYuv = new Mat(height + height/2, width, CvType.CV_8UC1);
mRgb = new Mat(height, width, CvType.CV_8UC3);
c. Process image in cbWithBuffer:
mYuv.put(0, 0, _data);
Imgproc.cvtColor(mYuv, mRgb, Imgproc.COLOR_YUV2RGB_NV21, 3);
processImage(mRgb.getNativeObjAddr());
d. Add function declaration
public native int processImage(long matAddrRgb);
e. Add image processing implementation in HelloWorld.cpp:
JNIEXPORT void JNICALL Java_org_ski_helloworld_MainActivity_processImage(JNIEnv*, jobject, jlong addrRgb)
{
Mat &rgb = *(Mat *) addrRgb;
int w = rgb.cols, h = rgb.rows;
Rect r(w/4,h/4,w/2,h/2);
Mat roi = rgb(r).clone();
Mat gray, edge;
cvtColor(roi, gray, CV_RGB2GRAY);
blur( gray, gray, Size(5,5));
Canny( gray, edge, 50, 150, 3);
edge.convertTo(gray, CV_8UC1);
cvtColor(gray,roi, CV_GRAY2RGB);
roi.copyTo(rgb(r));
}
The zipped project is HelloWorld_02.zip
