Change hue of image

Question

i have started working on opencv on android platform. I wanted to change the hue of image, not the whole just the sub part of it. So how we do that

• Change full image to hsv

• then select that specific part (Matrix)

• and change it's hue
• then convert the image back to rgba (i am working on android so it should b 4 channel. am i right??)

Or

• Select that sub part (Matrix)
• Change that sub part to hsv
• Change it's hue
• Convet back that specific part back to rgba

I have also try some code using second method i am not succeed yet. So i want some good examples or some guidance how to acheive that.

Answer 1

You can use OpenCV camera preview example from sample folder

Try below code

    //Global variable 
    private Mat src;
    Mat hsv = null;
    private CameraBridgeViewBase mOpenCvCameraView;

    List<Mat> hsv_channel= new ArrayList<Mat>();

    ---------------------------------------
    ----------------------------------------
// Initialize Mat here 
   public void onCameraViewStarted(int width, int height) {
        src = new Mat(height, width, CvType.CV_8UC4);
        hsv = new Mat(height, width, CvType.CV_8UC4);


     }
    -----------------------------------------
    ---------------------------------------
//Process Mat here
   public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
       src = inputFrame.rgba();  
       Imgproc.cvtColor(src, hsv,Imgproc.COLOR_BGR2HSV );     
       Core.split(hsv, hsv_channel);
       Imgproc.equalizeHist(hsv_channel.get(0), hsv_channel.get(0)); //Get hue channel and perform hsitogram equlization
       Core.merge(hsv_channel, hsv);
       Imgproc.cvtColor(hsv, src,Imgproc.COLOR_HSV2BGR );     

       return src;
    }