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JavaCV: Image Thresholding HSV color space

JavaCV (OpenCv) example of image thresholding based on color in HSV-A Space - to detect red color spot on given image. Useful in object tracking.

Java Source Code:

//imports
import static com.googlecode.javacv.cpp.opencv_core.*;
import static com.googlecode.javacv.cpp.opencv_highgui.*;
import static com.googlecode.javacv.cpp.opencv_imgproc.*;
import com.googlecode.javacv.cpp.opencv_core.CvScalar;
import com.googlecode.javacv.cpp.opencv_core.IplImage;

public class ColorDetect {
    // color range of red like color
    static int hueLowerR = 160;
    static int hueUpperR = 180;
    public static void main(String[] args) {
        IplImage orgImg = cvLoadImage("finding-red-color-spot.JPG");
        cvSaveImage("hsvthreshold.jpg", hsvThreshold(orgImg));

    }
    static IplImage hsvThreshold(IplImage orgImg) {
        // 8-bit, 3- color =(RGB)
        IplImage imgHSV = cvCreateImage(cvGetSize(orgImg), 8, 3);
        System.out.println(cvGetSize(orgImg));
        cvCvtColor(orgImg, imgHSV, CV_BGR2HSV);
        // 8-bit 1- color = monochrome
        IplImage imgThreshold = cvCreateImage(cvGetSize(orgImg), 8, 1);
        // cvScalar : ( H , S , V, A)
        cvInRangeS(imgHSV, cvScalar(hueLowerR, 100, 100, 0), cvScalar(hueUpperR, 255, 255, 0), imgThreshold);
        cvReleaseImage(imgHSV);
        cvSmooth(imgThreshold, imgThreshold, CV_MEDIAN, 13);
        // save
        return imgThreshold;
    }
}

Similar example but on RGB space is given here :

6 comments:

  1. UnknownMay 30, 2012 at 10:03 PM

    Are you making software based on
    image processing ? Then you need to threshold the image
    for initial background subtraction, this
    task is really cumbersome as it is
    dynamic. But no more! With help of this
    software you can change the
    threshold values dynamically while
    camera is capturing live images! In short everything is dynamic and
    live. Enjoy!

    sourceforge.net/projects/dthresh/

    Description
    With help of active trackbars you can
    change the values of RGB and HSV to
    threshold the live image feed from
    your camera!

    ReplyDelete
    Replies
    1. GTJune 10, 2012 at 6:06 AM

      Hi Dhaval, I tried using your app. But i could not run it at my Win7- 64bit machine.
      Its saying -
      The application has failed to start because its side-by-side configuration is incorrect. Please see the application event log or use the command-line sxstrace.exe tool for more detail.

      Thanks.

      Delete
  2. UnknownAugust 16, 2012 at 1:25 PM

    this example is give me a blank image....means a black image.
    what is the problem....??

    ReplyDelete
    Replies
    1. GTAugust 16, 2012 at 4:01 PM

      This code uses thresholding operation to detect red color spot on given image. You need to change the color range :

      static int hueLowerR = YOUR_VALUE_LOWER;
      static int hueUpperR = YOUR_VALUE_UPPER;

      Delete
  3. AnonymousSeptember 25, 2012 at 10:20 AM

    wht to do to detect all the position of the red spot in the image!!
    i am having a image with the multiple red spot

    ReplyDelete
  4. PaddyFebruary 8, 2013 at 6:42 PM

    Hi Ganesh ,
    Nice code thanks for the upload. If you dont mind my asking, in the line
    cvInRangeS(imgHSV, cvScalar(hueLowerR, 100, 100, 0), cvScalar(hueUpperR, 255, 255, 0), imgThreshold);

    WHy are there four variables ? and what would I need to change to make it detect green ??
    thanks
    Paddy

    ReplyDelete

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