I want to show camera and lines which I detected in real-time (using i.MX6 and Android 4.4). I use Android camera .addCallbackBuffer to get frame and use TextureView to show camera Preview.
JNI (C++) : get frame buffer->convert byte[] to Mat->than use OpenCV to do image processing
JNI can return Mat(use .getNativeObjAddr()) which already draw lines on it or return two coordinates which are the starting and ending points of the line
This code new Mat in JNI and hope to just return two coordinates. If this method can't work I will new Mat in JAVA and send .getNativeObjAddr() to JNI, then return Mat. Show Mat in TextureView?
Question: How to show camera preview and detected line at the same time using TextureView?
In MainActivity.java
public class MainActivity extends Activity implements TextureView.SurfaceTextureListener, PreviewCallback {
protected Camera mCamera;
private TextureView mTextureView;
public byte[][] cameraBuffer;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
mTextureView = new TextureView(this);
mTextureView.setSurfaceTextureListener(this);
setContentView(mTextureView);
}
....
@Override
public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
mCamera = Camera.open(0);
int bufferSize = mCamera.getParameters().getPictureSize().width * mCamera.getParameters().getPictureSize().height
* ImageFormat.getBitsPerPixel(mCamera.getParameters().getPreviewFormat()) / 8;
cameraBuffer = new byte[3][bufferSize];
thread = new getFrameThread( this, kCameraWidth, kCameraHeight);
for (int i = 0; i < 3; ++i)
mCamera.addCallbackBuffer(cameraBuffer[i]);
mCamera.setPreviewCallbackWithBuffer(this);
thread.start();
if (mCamera == null) {
throw new RuntimeException("Default camera not available");
}
try {
mCamera.setPreviewTexture(surface);
mCamera.startPreview();
} catch (IOException ioe) {
// Something bad happened
}
}
@Override
public void onPreviewFrame(byte[] data, Camera camera) {
// TODO Auto-generated method stub
camera.addCallbackBuffer(data);//callback data to cameraBuffer
thread.refresh(data, countFrame);//send new frame data to JNI
}
....
static {
System.loadLibrary("opencv_java"); //load opencv_java lib
System.loadLibrary("testLib");
}
public native void getRawFrame(byte[] data,int width, int height, int count);
}
In getFrameThread (thread to run JNI function 'getRawFrame' )
public class getFrameThread extends Thread{
public byte[] data;
{
.....
mainActivity.getRawFrame(data, 480, 720);
.....
}
public void refresh(byte[] data, int countFrame){
this.data = data;
}
}
In JNI
#include <jni.h>
#include <stdio.h>
#include <stdlib.h>
#include <opencv2/opencv.hpp>
using namespace cv;
extern"C"
{
.....
JNIEXPORT void JNICALL Java_com_example_adas_MainActivity_getRawFrame( JNIEnv* env, jobject thisobject,
jbyteArray data, jint width, jint height){
int length = env->GetArrayLength(data);
unsigned char *bufferIn = (unsigned char*) env->GetPrimitiveArrayCritical(data, NULL);
yuvMat = Mat(height * 3/2, width, CV_8UC1, bufferIn);
cvtColor(yuvMat, grayMat, cv::COLOR_YUV2GRAY_I420);
//Do lines detected
.....
env->ReleasePrimitiveArrayCritical(data, bufferIn, JNI_ABORT);
}
