Develop Reference

How to disable/modify AutoFocus and AutoWhiteBalance on Android Camera using OpenCV

I'm using Android + Opencv(new to opencv) and I'm currently working with real time object detection (the object stays really close to the android device Camera) , and I noticed that the Android camera's autoFocus keeps modifying my frames (kind of 'zoom in' and 'zoom out' effect) which make it harder for me to keep tracking the object.
I need to turn the "AUTO FOCUS" off because in my case the more blurred image input I have, the better, and I also need to turn the AutoWhiteBalance off as well, or maybe set to a different value.
I would like to know how to do it through my OpenCV CameraBridgeViewBase so I could modify the camera's Focus/WhiteBalance settings.
I've trying to find a way to solve it, and I noticed that many people face the same problems.
Here, at Stack Overflow, would be a great place to find someone who have worked with that and found a good way to overcome these problems.

create your own subclass of javacameraview
public class MyJavaCameraView extends JavaCameraView {
where you can have access to mCamera;
add whatever camera access using method you are interested in
for example
// Setup the camera
public void setFlashMode(boolean flashLightON) {
Camera camera = mCamera;
if (camera != null) {
Camera.Parameters params = camera.getParameters();
params.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
camera.setParameters(params);
and use this new class as part of the main activity
//force java camera
mOpenCvCameraView = (MyJavaCameraView) findViewById(R.id.activity_surface_view);
mOpenCvCameraView.setVisibility(SurfaceView.VISIBLE);
mOpenCvCameraView.setCvCameraViewListener(this);
mOpenCvCameraView.enableView();

How to turn on the flash led continuously using FLASH_MODE_ON?

I searched on the web to turn on the flash using this mode but no solution work so far... I want to use this mode because some devices doesn't support the FLASH_MODE_TORCH, so I want to force the focus or another thing to turn on the flash continuously. I tried to restart the "autofocus" when the flash turns off automatically but it takes too much time (the period between two "flashing" is quite long).
So I ask you if you know some way to do it, thanks ! :)
Actually I use :
public static Camera Cam;
public static Parameters CamParams;
Cam = Camera.open();
CamParams = Cam.getParameters();
CamParams.setFlashMod(Parameters.FLASH_MODE_ON);
Cam.setParameters(CamParams);
Cam.startPreview();
Cam.autoFocus(new AutoFocusCallback()
{
public void onAutoFocus(boolean success, Camera camera)
{}
});

Does Face Detection require a SurfaceView to work?

Using API 14 I have created an Activity which uses face detection successfully (I'm a bit of a newb at this Face Detection stuff).
I don't want to show the preview of the Camera however; I just want to know when the user's face is in front of the camera. I added a few buttons to make the SurfaceView Visible/Invisible and I found that the face detection stops working when it is INVISIBLE or GONE.
Is there a way to enable the face detection without requiring the SurfaceView in the layout?
Here is how I have coded it:
mCamera.setPreviewDisplay(mSurfaceHolder);
mCamera.startPreview();
if(mCamera.getParameters().getMaxNumDetectedFaces() >0) {
mCamera.setFaceDetectionListener(new Camera.FaceDetectionListener() {
#Override public void onFaceDetection(Face[] faces, Camera camera) {
if(faces.length > 0) {
System.out.println("Found someone");
}
}
});
mCamera.startFaceDetection();
}
To hide the surfaceview I have added a black View. :-)
<View android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#000"/>
I've had a reasonable look around and I haven't found much code using startFaceDetection() yet.
Thanks for any ideas / help.

You should rather use a dummy SurfaceTexture for your purposes.
Just create a SurfaceTexture object by passing any integer such as
mSurfaceTexture = new SurfaceTexture(1);
Now, open your camera and do the following:
mCamera = Camera.open(Camera.CameraInfo.CAMERA_FACING_FRONT);
try{
mCamera.setPreviewTexture(mSurfaceTexture);
}
catch (IOException t) {
//Do Something here
}
3) You can do everything else just the same way i.e. using face detection.

The Camera Preview doesn't get displayed if you omit
setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
I have not yet tested this with Face Detection (no 4.0 device and the emulator doesn't yet support it). But it should work.
Reference: https://groups.google.com/forum/?fromgroups#!topic/android-developers/EzBgJRetaCo
You could also attempt to use setPreviewTexture(SurfaceTexture st) instead of setPreviewDisplay and use a SurfaceTexture that you can control.

ColorEffect not visible on camera preview

I am trying to get a camera preview with a color effect applied to it, such as for example the NEGATIVE effect. There are no errors, and the preview is visible without problems, but independent of the ColorEffect I set - the camera preview remains unchanged. I tested if the effects I am trying to use are available to my phone by running params.getSupportedColorEffects() (also these effects also work in the built in photo app).
I have no idea what is wrong with the code - I am posting it below. Perhaps someone here has an idea what could make this work? Thanks in advance.
public class CustomCameraView extends SurfaceView{
Camera mCamera;
SurfaceHolder mHolder;
public CustomCameraView(Context context){
super(context);
mHolder = this.getHolder();
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
mHolder.addCallback(mSurfaceHolderListener);
}
SurfaceHolder.Callback mSurfaceHolderListener = new SurfaceHolder.Callback() {
public void surfaceCreated(SurfaceHolder holder) {
mCamera=Camera.open();
try {
mCamera.setPreviewDisplay(mHolder);
}
catch (Exception e){ }
}
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height)
{
Camera.Parameters params = mCamera.getParameters();
params.setColorEffect(Camera.Parameters.EFFECT_NEGATIVE);
mCamera.setParameters(params);
mCamera.startPreview();
}
public void surfaceDestroyed(SurfaceHolder arg0)
{
mCamera.stopPreview();
mCamera.release();
}
};
}
After some testing it turned out the problem could be related to the HTC Desire I was testing on (or maybe its OS version). The code works correctly on some other Samsung phones. I haven't figured out what could be the problem on the HTC.
UPDATE:
I have managed to get the effects working, but truly by accident, and I still don't understand why. But I will give the answer here - perhaps someone will find it useful, or maybe will be able to explain why it happens this way:
I added the following line to the surfaceChanged method because I was trying to decrease the size of the preview:
previewHolder.setFixedSize(width, height-1);
This had the result of making the selected effect visible.
When I changed this line to:
previewHolder.setFixedSize(width, height);
the effect was not visible any more once again. So odd.... it works for set height being anything less than the received height parameter.

I have been struggling with this as well. I found out that the HTC Desire its camera needs a strange order of executing the setParameters, setPreviewDisplay and startPreview for the color effect to work. The order is:
Camera.Parameters parameters = camera.getParameters();
//set the parameters
camera.setParameters(parameters);
camera.startPreview();
camera.setParameters(parameters);
camera.setPreviewDisplay(surfaceHolder);
Calling startPreview before setPreviewDisplay is documented in the Android SDK as a way of initializing the camera and the surfaceView in parallel.
Regarding your update about getting the effects to work by accident, the same happend to me! I assume for the same reason, some of my code got called twice in quick succesion (in my case due to a changing database object). This caused the method to (re)set the parameters and (re)start the preview to be called twice producing the desired result. After realising this and some more experimenting the above order seemed to work on both my HTC Desire and Acer Iconia A500 and I was quite happy with it.
However I have just received a comment for my application saying it produces corrupted images on the HTC Desire HD so I would recommend not using this order of camera initialization as a default but rather as a fix for the HTC Desire.

After setting new parameters to camera and starting preview invalidate() are calling on your SurfaceView . But it only Invalidate the whole view. If the view is visible, onDraw(android.graphics.Canvas) will be called at some point in the future. So there is no guarantees that onDraw() will be called immediately. But onDraw() are always invoking after calling onMeasure() with size differs from current. So it can be a reason of this odd behavior.

Simple answers use following type :
Camera camera = null;
camera = Camera.open();
if (camera != null) {
try {
Camera.Parameters parameters = camera.getParameters();
// Set all kind of stuffs here..
parameters.setSceneMode(Camera.Parameters.FLASH_MODE_AUTO);
parameters.setColorEffect(Camera.Parameters.EFFECT_SEPIA); // whatever effect you want
camera.setParameters(parameters);
camera.setPreviewDisplay(surface_holder);
camera.startPreview();
} catch (IOException exception) {
camera.release();
camera = null;
}
}

Using Camera in Portrait Orientation

I'm trying to develop an app which uses the Camera. So far it's been working well, except that I'm unable to force the orientation to be "portrait". It seems to work well if I force all activities to "landscape", because the camera preview seems to fit in landscape.
Is there anyway to use the Camera in portrait mode?

Android devices v2.2 and above contain and API to rotate the display to portrait. Devices below 2.2 are landscape only. Your best bet is to detect if the device is 2.2 and rotate 90 degrees. Fall back on landscape for devices under 2.2. The good news is most Android devices are on 2.2 and above.
Check out my answer here for more info:
Camera is wrong unless keyboard is open

public void surfaceCreated(SurfaceHolder holder)
{
// The Surface has been created, acquire the camera and tell it where to draw.
mCamera = Camera.open();
Parameters params = mCamera.getParameters();
if (this.getResources().getConfiguration().orientation != Configuration.ORIENTATION_LANDSCAPE)
{
params.set("orientation", "portrait");
mCamera.setDisplayOrientation(90);
}
try
{
mCamera.setPreviewDisplay(holder);
}
catch (IOException exception)
{
mCamera.release();
mCamera = null;
}
}

edit: I was in the midst of Adobe AIR for Android development when I answered this question, and looking back at it, I realize this question didn't pertain to Adobe AIR.
Adobe says:
On devices that can change the screen orientation, such as mobile phones, a Video object attached to the camera will only show upright video in a landscape-aspect orientation. Thus, mobile apps should use a landscape orientation when displaying video and should not auto-rotate.
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/media/Camera.html
If you do really want to use the camera in portrait mode, my suggestion is to rotate the video object.
Here's some sample code that rotates the video object (_video) by an angle in degrees (source was pulled from elsewhere on stackoverflow):
var matrix:Matrix = _video.transform.matrix;
var rect:Rectangle = _video.getBounds(this);
matrix.translate(- (rect.left + (rect.width/2)), - (rect.top + (rect.height/2)));
matrix.rotate((angle/180)*Math.PI);
matrix.translate(rect.left + (rect.width/2), rect.top + (rect.height/2));
_video.transform.matrix = matrix;