how to count frequency of the color?

[meth]

hi, i want to convert a color image to a greyscale image by counting the frequency of the color (0-255) and put the frequency in an array but im stuck with putting it into the array. can anyone pls help me what do i have to do next? thx in advance.

public class Freq extends javax.swing.JFrame {
    Image inputimage, output_rgb;
    BufferedImage buff_in, buff_grey;

    int counter;
    int width = 256; //initial image width pixel
    int height = 256; //initial image height pixel

    File file_input, file_output;

    JFileChooser fileopen = new JFileChooser();
    JFileChooser filesave= new JFileChooser();
    FileFilter filter = new FileNameExtensionFilter("image files","jpg");                       

    private void openbuttonActionPerformed(<em>java</em>.awt.event.ActionEvent evt) {                                           
        fileopen.addChoosableFileFilter(filter);

        int return_value = fileopen.showOpenDialog(this);

        if (return_value == JFileChooser.APPROVE_OPTION)
        {
            file_input = fileopen.getSelectedFile();
            System.out.println(file_input);
        }
        try
        {
            inputimage = ImageIO.read(file_input);
            inputimage = inputimage.getScaledInstance(256,256,Image.SCALE_SMOOTH);
            repaint();
        } 
        catch(IOException e)
        {
            System.out.println("ERROR");
        }
}                                          

    public void paint(Graphics g)
    {
        g.drawImage(inputimage,100,100,this);
    }                                    

    private void processActionPerformed(<em>java</em>.awt.event.ActionEvent evt) {                                        
        width = inputimage.getWidth(null);
        height = inputimage.getHeight(null);
        buff_grey = new BufferedImage(width,height,BufferedImage.TYPE_BYTE_GRAY);
        Graphics gr = buff_grey.getGraphics();
        gr.drawImage(inputimage,0,0,null);
        gr.dispose();

        process_input = new int[width * height];
        process_grey = new int[width * height];
        counter = 0;
        for (int i = 0; i < 256; i++)
        {
            for (int j = 0; j < 256; j++)
            {
                int clr = buff_grey.getRGB(j,i);
                int red = (clr & 0x00ff0000) >> 16;
                int green = (clr & 0x0000ff00) >> 8;
                int blue = clr & 0x000000ff;
                int grey = (red + green + blue)/3;
                process_input[counter] = clr;
                process_grey[counter] = grey;
                counter++;
            }
        }
        repaint();

//is this where i have to write the array for the frequency?
}

[JosAH]

I don't see the problem: if you have a gray value in the range [0, 255] an array of 255 elements can store the frequencies:

int[] freqs[]= new int[256];
...
int gray= ...; // any value in the range [0, 255]
...
freqs[gray]++; // update the frequency for gray value 'gray'.

Update the array for all gray values in your image and voila.

kind regards,

Jos

[meth]

sir, i have the code as follow:

public static BufferedImage equalizeGrayScale(BufferedImage imageIn)
	{
		BufferedImage imageOut = new BufferedImage(256,256, BufferedImage.TYPE_BYTE_GRAY);
		
		int[] frequency = new int[256];
		int maxIntensity = 255;
		
		for(int x = 0; x < imageIn.getWidth(); x++)
		{
			for(int y = 0; y <imageIn.getHeight(); y++)
			{
				double[] pixel = new double[1];
				pixel = imageIn.getRaster().getPixel(x, y, pixel);
				frequency[(int)pixel[0]]++;
			}
		}
		
		int sum = 0;
		for (int x = 0; x < frequency.length; x++)
		{
			sum += frequency[x];
			frequency[x] = sum * maxIntensity /(256 * 256);
		}
		
		for (int x = 0; x <imageIn.getWidth(); x++)
		{
			for (int y = 0; y < imageIn.getHeight(); y++)
			{
				double[] pixel = new double[1];
				pixel = imageIn.getRaster().getPixel(x,y,pixel);
				pixel[0] = frequency[(int)pixel[0]];
				imageOut.getRaster().setPixel(x, y, pixel);
			}
		} 
	
		return imageOut;
	}

is it the one that i need?

[meth]

ok i got it now :)

[kzzaman]

I can't understand the above code.plz define how to count the frequency in a image...