Use OpenCV to show camera on android App with correct orientation

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In this series of tutorials, you are learning OpenCV for Android using Android Studio. So far, you have made a working OpenCV Android Studio Project containing OpenCV module.

In Here is the overview of what we are going to achieve:

  • Create an OpenCV for Android Project (As in previous tutorial in this series) (Here)
  • Show Camera on the Screen
    1. Edit Manifest
      1. Add permission to allow camera.
      2. Support various screen sizes and adaptability of camera.
      3. Use specific features of the camera.
    2. Add a custom Layout show_camera.xml to display camera in it.
    3. Edit MainActivity_show_camera.java 
      1. Import required android classes
      2.  Import OpenCV classes
      3. Connect to OpenCV manager
      4. Initiate LogCat to log events of out app
      5. SHOW CAMERA ON LAYOUT
      6. Corrected Orientation (portrait)

Trust me, it is very simple to do. Lets do it!


 

Manifest.xml

We need to edit the AndroidManifest.xml file like following:

  1. Allow permission to use camera
  2. Allow camera to optimize to the dimensions of the device in use
  3. Use Front camera and autofocus of camera :S

The Manifest.xml file in its entirety is given here

 

This entire process is given here:

Show camera on android App using OpenCV for Android - Edit Manifest

This is all you need to do in AndroidManifest.xml


Create a new layout (show_camera.xml )

Now in your project, do the following:

  1. Create a new layout called show_camera.xml
  2. Add the following code it to:

    Note that the JavaCameraView has the id of show_camera_activity_java_surface_view

This is given below:

 


MainActivity_show_camera.java

Import the following Android Classes in your MainActivity_show_camera:

Import the following OpenCV classes in your MainActivity_show_camera:

Now, lets work with the MainActivity_show_camera Class 🙂 (Code in the end). I will explain every line of OpenCV code in detail.

  • Implement the OpenCV class CvCameraViewListener2 to allow OpenCV to communicate with android camera functionalities.

  • Declare the following items in the class
  • Now, lets call OpenCV manager to help our app communicate with android phone to make OpenCV work

    • CameraBridgeViewBase mOpenCvCameraView
      This variable acts as a bridge between camera and OpenCV library.
    • BaseLoaderCallback mLoaderCallback = …..
      Well, once OpenCV library is loaded, you may want to perform some actions. For example, displaying a success or failure message.
  • Initiate the LogCat
  • Now, when the activity is created, display the OpenCV camera in the layout. show_camera.xml.
  •  The following three functions handle the events when the app is Paused, Resumed and Closed/Destroyed
  • Now, we will do two main things:
    • Receive Image Data when the camera preview starts on your screen 😀
    • Destroy image data when you stop camera preview on your phone screen
    • Now, this one is interesting! OpenCV orients the camera to left by 90 degrees. So if the app is in portrait more, camera will be in -90 or 270 degrees orientation. We fix that in the next and the most important function. There you go!

The entire code is given below:

The entire process of editing MainActivity_show_camera.java is shown here:

Show camera on android App using OpenCV for Android - MainActivity_show_camera


Note: The camera disorientation problem is a bitch an issue not to be takien lightheartedly. Thanks for noting.

This concludes this tutorial, now that you have created a camera app, it is now time to continue this and perform more Computer Vision! In the next tutorial, I will draw a simple object on the screen. Be sure to check out the list of OpenCV for Android tutorials for latest tutorials.

Thanks for reading, and please share and comment if this helped and to share your ideas and opinions.

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