ConvolutionFilter.java | Kernel Image Processing in Java

// ConvolutionFilter.java
// Author: Abdul Fatir
// E-Mail: [email protected]

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.awt.Color;
import java.io.File;
import java.io.InputStreamReader;
import java.io.BufferedReader;
import java.io.IOException;
import static java.lang.System.out;
public class ConvolutionFilter
{
    public static String filename = "raw.png";
    public static void main(String args[])throws IOException
    {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        out.print("Kernel Order:");
        int order = Integer.parseInt(reader.readLine());

        float[][] kernel = new float[order][order];
        float sum_of_elements = 0.0f;
        float mult_factor = 1.0f;
        float bias = 0f;

        // Getting the Kernel Matrix as input from the user
        for(int i=0; i < order; i++)
        for(int j=0; j < order; j++)
        {
            out.print(i+","+j+":");
            kernel[i][j] = Float.parseFloat(reader.readLine());
        }

        out.println("\nThe Kernel Matrix is:\n");

        for(int i=0; i < order; i++)
        {
            for(int j=0; j < order; j++)
            {
                out.print("\t"+kernel[i][j]);
                sum_of_elements += kernel[i][j];
            }
            out.println();
        }

        out.println("\nThe sum of matrix elements is: "+sum_of_elements);

        // mult_factor is the value with which each computed sum is multiplied
        // mult_factor = 1 gives no changes to input kernel matrix
        out.print("\nMultlipication Factor: ");
        mult_factor = Float.parseFloat(reader.readLine());

        // Bias can be added to increase brightness of the image
        // bias = 0 gives no change in brightness if the sum_of_elements is 1
        out.print("Bias: ");
        bias = Float.parseFloat(reader.readLine());

        BufferedImage input,output;

        input = ImageIO.read(new File(filename));
        int WIDTH = input.getWidth();
        int HEIGHT = input.getHeight();

        output = new BufferedImage(WIDTH, HEIGHT, input.getType());
        out.println("[*] Rendering the image...");
        for(int x=0;x<WIDTH;x++)
        {
            for(int y=0;y<HEIGHT;y++)
            {
                float red=0f,green=0f,blue=0f;
                for(int i=0;i<order;i++)
                {
                    for(int j=0;j<order;j++)
                    {
                        // Calculating X and Y coordinates of the pixel to be multiplied with current kernel element
                        // In case of edges of image the '% WIDTH' wraps the image and the pixel from opposite edge is used
                        int imageX = (x - order / 2 + i + WIDTH) % WIDTH;
                        int imageY = (y - order / 2 + j + HEIGHT) % HEIGHT;

                        int RGB = input.getRGB(imageX,imageY);
                        int R = (RGB >> 16) & 0xff; // Red Value
                        int G = (RGB >> 8) & 0xff;  // Green Value
                        int B = (RGB) & 0xff;       // Blue Value

                        // The RGB is multiplied with current kernel element and added on to the variables red, blue and green
                        red += (R*kernel[i][j]);
                        green += (G*kernel[i][j]);
                        blue += (B*kernel[i][j]);
                    }
                }
                int outR, outG, outB;
                // The value is truncated to 0 and 255 if it goes beyond
                outR = Math.min(Math.max((int)(red*mult_factor),0),255);
                outG = Math.min(Math.max((int)(green*mult_factor),0),255);
                outB = Math.min(Math.max((int)(blue*mult_factor),0),255);
                // Pixel is written to output image
                output.setRGB(x,y,new Color(outR,outG,outB).getRGB());
            }
        }
        out.print("[?] Save file as:");
        String outputfname = reader.readLine();
        ImageIO.write(output,"PNG", new File(outputfname+".png"));
        out.print("[+] File saved as "+outputfname+".png");
    }

}