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.
In this post, I’m going to show you how to detect a red‑colored spot in an image using JavaCV (OpenCV) and HSV color space thresholding – a building block for many object tracking applications.

Instead of struggling with RGB values that change drastically under different lighting, we switch to the HSV color model. Hue (H) represents the pure pigment, while Saturation and Value are separated. That makes color filtering far more robust. Red is special: its hue wraps around 0°, so the full range is 0–10° and 160–180°. In this example we target only the upper range (160–180) for bright red.

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 {

Java Sound : audio inputstream from pcm amplitude array

In this post, i am going to show the code for creating the AudioInputStream from an PCM - amplitude array. It basically converts the int [] array to byte array according to AudioFormat.

The code for the reverse operation (extract amplitude array from recorded wave file or AudioStream )is in my earlier post : http://ganeshtiwaridotcomdotnp.blogspot.com/2011/12/java-extract-amplitude-array-from.html

The code for converting PCM amplitude array to AudioStream is follows :

Java Sound : generate play sine wave - source code

Working source code example on how to generate and play sine wave in Java :
View my previous post  for playing any PCM amplitude array.

Generate Sine wave of a particular frequency :

    private static byte[] generateSineWavefreq(int frequencyOfSignal, int seconds) {
        // total samples = (duration in second) * (samples per second)
        byte[] sin = new byte[seconds * sampleRate];
        double samplingInterval = (double) (sampleRate / frequencyOfSignal);
        System.out.println("Sampling Frequency  : "+sampleRate);
        System.out.println("Frequency of Signal : "+frequencyOfSignal);
        System.out.println("Sampling Interval   : "+samplingInterval);
        for (int i = 0; i < sin.length; i++) {
            double angle = (2.0 * Math.PI * i) / samplingInterval;
            sin[i] = (byte) (Math.sin(angle) * 127);
            System.out.println("" + sin[i]);
        }

Java Audio : Playing PCM amplitude Array

Play an Array of PCM Amplitude Values in Java – Quick Tutorial

Basic Steps:

// Initialize a SourceDataLine for playback
SourceDataLine line = AudioSystem.getSourceDataLine(audioFormat);
line.open(audioFormat);
line.start();

// Write the entire byte array to the line
line.write(byteArray, 0, byteArray.length);
line.drain();
line.close();

Converting integer or float arrays to a byte array:
The line.write() method expects a byte[], so your raw PCM amplitude values must be packed accordingly. The conversion depends on the audio format you choose. For 8‑bit signed PCM (what we’ll use in the example), a normalised float between -1 and 1 maps to a single byte with (byte)(amplitude * 127). For 16‑bit signed, you’d need to write two bytes per sample in the correct endian order. The snippet below shows the simple 8‑bit mapping.

Java extract amplitude array from recorded wave

Extract amplitude array from recorded/saved wav : From File , AudioInputStream , ByteArray of File or ByteArrayInputStream - working java source code example

 import java.io.ByteArrayInputStream;  
 import java.io.File;  

Sound (audio file) player in java - working source code example

Sound (audio file) player in java - working source code example

 import java.io.File;  
 import java.io.IOException;  
 import javax.sound.sampled.AudioFormat;  
 import javax.sound.sampled.AudioInputStream;  
 import javax.sound.sampled.AudioSystem;  
 import javax.sound.sampled.DataLine;  

Java Sound Capture from Microphone working code

Sound Capture: Record from Microphone and Save — Complete Java Example

 import java.io.ByteArrayInputStream;  
 import java.io.ByteArrayOutputStream;  
 import java.io.IOException;  
 import javax.sound.sampled.AudioFormat;  
 import javax.sound.sampled.AudioInputStream;  
 import javax.sound.sampled.AudioSystem;  
 import javax.sound.sampled.DataLine;  
 import javax.sound.sampled.TargetDataLine;  
 /**  
  * Reads data from the input channel and writes to the output stream  
  */  
 public class MicrophoneRecorder implements Runnable {  
   // record microphone && generate stream/byte array  
   private AudioInputStream audioInputStream;  

Java Reflection - Getting name of color without comparision

In this tutorial I am describing how get value of field/ property defined in class dynamically using Java Reflection.
And i am using it to get name of color (java.awt.Color) using Reflection.

Instead of doing lengthy comparison (shown below), we can do this easily by using java reflection:

   public static String getNameReflection(Color colorParam) {
        try {
            //first read all fields in array
            Field[] field = Class.forName("java.awt.Color").getDeclaredFields();
            for (Field f : field) {
                String colorName = f.getName();
                Class<?> t = f.getType();
                // System.out.println(f.getType());
                // check only for constants - "public static final Color"
                if (t == java.awt.Color.class) {
                    Color defined = (Color) f.get(null);
                    if (defined.equals(colorParam)) {
                        System.out.println(colorName);
                        return colorName.toUpperCase();
                    }
                }
            }
        } catch (Exception e) {
            System.out.println("Error... " + e.toString());
        }
        return "NO_MATCH";
    }

Getting name of color by Comparision
One solution to get name of color may be by comparison like this :

    public static String getNameByComparision(Color color) {
        if (color.equals(Color.RED)) {
            return "RED";
        }
        if (color.equals(Color.BLACK)) {
            return "BLACK";
        }
        // ..
        return "NOT_DEFINED";
    }

cygwin: access windows disk, directories and files

Cygwin puts a Linux‑like shell on your Windows desktop. In this quick tip, I’ll show you how to browse your Windows drives and files straight from the Cygwin terminal.

Java: Screen Capture using Robot and save

Robot : java.awt.Robot  is used to take control of the mouse and keyboard. It is used for test automation, self-running demos and screen capture at various state of execution of the program.
Java Code for detecting screen size and capturing whole screen using Robot and saving :