Camera focus distances

Question

I'm trying to read the focus distance (distance of subject in a photo) from an Android camera. I keep getting 0 for all focus distances on my HTC Desire even when it correctly autofocuses. Here's the whole app, only works on v2.3.3 and above.

ImageCapture.java

package test.test;

import java.io.IOException;
import java.io.OutputStream;
import java.text.SimpleDateFormat;

import android.app.Activity;
import android.content.Intent;
import android.graphics.PixelFormat;
import android.hardware.Camera;
import android.hardware.Camera.AutoFocusCallback;
import android.hardware.Camera.PictureCallback;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore.Images.Media;
import android.util.Log;
import android.view.KeyEvent;
import android.view.MenuItem;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

//THIS CLASS READS THE FOCUS DISTANCES
class ImageFocusCallback implements AutoFocusCallback {
    @Override
    public void onAutoFocus(boolean success, Camera camera) {
        //READ FOCUS DISTANCES HERE
        Camera.Parameters parameters = camera.getParameters();
        float[] distances = new float[3];
        if (success) {
            // Only available with Android 9 (2.3)
            // Focus Mode is always reported as auto but
            // distances do not appear to be updating
            // always: 0.1, 1.2, Infinity, (on my device it's 0,0,0)
            Log.d("Focus Mode: ", parameters.getFocusMode());
            parameters.getFocusDistances(distances);
            Log.d("focus distance near", Float.toString(distances[0]));
            Log.d("focus distance optimum", Float.toString(distances[1]));
            Log.d("focus distance far", Float.toString(distances[2]));
        }
    }
}

public class ImageCapture extends Activity implements SurfaceHolder.Callback {
    //CALL AUTO FOCUS HERE
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) {
            ImageFocusCallback autoFocusCallBack = new ImageFocusCallback();
            //AUTOFOCUS IS CALLED HERE
            camera.autoFocus(autoFocusCallBack);
            return true;
        }
        return false;
    }

    //REST OF THE CODE
    private Camera           camera;
    private boolean          isPreviewRunning = false;
    private SimpleDateFormat timeStampFormat  = new SimpleDateFormat("yyyyMMddHHmmssSS");

    private SurfaceView      surfaceView;
    private SurfaceHolder    surfaceHolder;
    private Uri              target           = Media.EXTERNAL_CONTENT_URI;


    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        Log.e(getClass().getSimpleName(), "onCreate");
        getWindow().setFormat(PixelFormat.TRANSLUCENT);
        setContentView(R.layout.main);
        surfaceView = (SurfaceView) findViewById(R.id.surface);
        surfaceHolder = surfaceView.getHolder();
        surfaceHolder.addCallback(this);
        surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

    }

    @Override
    public boolean onCreateOptionsMenu(android.view.Menu menu) {
        MenuItem item = menu.add(0, 0, 0, "goto gallery");
        item.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem item) {
                Intent intent = new Intent(Intent.ACTION_VIEW, target);
                startActivity(intent);
                return true;
            }
        });
        return true;
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
    }

    Camera.PictureCallback mPictureCallbackRaw  = new Camera.PictureCallback() {
                                                    @Override
                                                    public void onPictureTaken(byte[] data, Camera c) {
                                                        Log.e(getClass().getSimpleName(), "PICTURE CALLBACK RAW: " + data);
                                                        camera.startPreview();
                                                    }
                                                };

    Camera.PictureCallback mPictureCallbackJpeg = new Camera.PictureCallback() {
                                                    @Override
                                                    public void onPictureTaken(byte[] data, Camera c) {
                                                        Log.e(getClass().getSimpleName(), "PICTURE CALLBACK JPEG: data.length = " + data);
                                                    }
                                                };

    Camera.ShutterCallback mShutterCallback     = new Camera.ShutterCallback() {
                                                    @Override
                                                    public void onShutter() {
                                                        Log.e(getClass().getSimpleName(), "SHUTTER CALLBACK");
                                                    }
                                                };




    // ImageCaptureCallback iccb = null;
    // if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) {
    // try {
    // String filename = timeStampFormat.format(new Date());
    // ContentValues values = new ContentValues();
    // values.put(Media.TITLE, filename);
    // values.put(Media.DESCRIPTION, "Image capture by camera");
    // Uri uri = getContentResolver().insert(Media.EXTERNAL_CONTENT_URI,
    // values);
    // // String filename = timeStampFormat.format(new Date());
    // iccb = new
    // ImageCaptureCallback(getContentResolver().openOutputStream(uri));
    // } catch (Exception ex) {
    // ex.printStackTrace();
    // Log.e(getClass().getSimpleName(), ex.getMessage(), ex);
    // }
    // }
    // if (keyCode == KeyEvent.KEYCODE_BACK) {
    // return super.onKeyDown(keyCode, event);
    // }
    //
    // if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) {
    // camera.takePicture(mShutterCallback, mPictureCallbackRaw, iccb);
    // return true;
    // }
    //
    // return false;
    // }

    @Override
    protected void onResume() {
        Log.e(getClass().getSimpleName(), "onResume");
        super.onResume();
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
    }

    @Override
    protected void onStop() {
        Log.e(getClass().getSimpleName(), "onStop");
        super.onStop();
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        Log.e(getClass().getSimpleName(), "surfaceCreated");
        camera = Camera.open();
        Camera.Parameters parameters = camera.getParameters();
        float[] distances = new float[3];
        Log.d("Focus Mode: ", parameters.getFocusMode());
        parameters.getFocusDistances(distances);
        Log.d("focus distance 0", Float.toString(distances[0]));
        Log.d("focus distance 1", Float.toString(distances[1]));
        Log.d("focus distance 2", Float.toString(distances[2]));
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        Log.e(getClass().getSimpleName(), "surfaceChanged");
        if (isPreviewRunning) {
            camera.stopPreview();
        }
        Camera.Parameters p = camera.getParameters();
        p.setPreviewSize(w, h);
        camera.setParameters(p);
        try {
            camera.setPreviewDisplay(holder);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        camera.startPreview();
        isPreviewRunning = true;
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        Log.e(getClass().getSimpleName(), "surfaceDestroyed");
        camera.stopPreview();
        isPreviewRunning = false;
        camera.release();
    }

}



class ImageCaptureCallback implements PictureCallback {

    private OutputStream filoutputStream;

    public ImageCaptureCallback(OutputStream filoutputStream) {
        this.filoutputStream = filoutputStream;
    }

    @Override
    public void onPictureTaken(byte[] data, Camera camera) {
        try {
            Log.v(getClass().getSimpleName(), "onPictureTaken=" + data + " length = " + data.length);
            filoutputStream.write(data);
            filoutputStream.flush();
            filoutputStream.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

}
}

main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:orientation="vertical">
    <SurfaceView android:id="@+id/surface" 
    android:layout_width="fill_parent"
        android:layout_height="10dip" 
        android:layout_weight="1">
    </SurfaceView>
</LinearLayout>  

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="test.test"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="10" />
    <uses-permission android:name="android.permission.CAMERA" />
    <uses-feature android:name="android.hardware.camera" />
 <uses-feature android:name="android.hardware.camera.autofocus" />

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".ImageCapture"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>
</manifest>

Could it be that that there is a bug in the device driver? In the Android source Camera.java call native_autoFocus() and native_getParameters() to read the distances. Does anyone know where to get the source for the native calls?

Answer 1

In Froyo, frameworks/base/core/jni/android_hardware_Camera.cpp implements native_autoFocus() by calling android_hardware_Camera_autoFocus(), which appears to bind at runtime to the device/vendor specific code.

Unfortunately, "If the camera does not support auto-focus and autoFocus is called, onAutoFocus will be called immediately with a fake value of success set to true." is a documented behavior.

I'm curious which of the functions you use requires 2.3.3, API level 10.