Homography matrix

static double x1,y1,x2,y2,x3,y3,x4,y4,X1,Y1,X2,Y2,X3,Y3,X4,Y4;


    public static void main(String[] args) {

        /*
        * read image
        */
        BufferedImage imgBuffer = null;
        try {
            imgBuffer = ImageIO.read(new File("C:\\Users\\mohar\\Desktop\\test\\3.jpg"));
        } catch (IOException ex) {
            Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
        }


//        int rgb_val = imgBuffer.getRGB(9, 9);
//        System.out.println(imgBuffer.getWidth());
//        System.out.println(imgBuffer.getHeight());
//        Color p = new Color(rgb_val);
//        System.out.println(p.getRed());
//        System.out.println(p.getGreen());
//        System.out.println(p.getBlue());

        /*
        * scale image
        */
        /*File output = new File("G:\\matlab practise\\output.jpg");
        try {
            ImageIO.write(sclae2(imgBuffer, 1000, 1280), "jpg", output);
        } catch (IOException ex) {
            Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
        }*/


        x1 = 319;
        y1 = 558;
        x2 = 1527;
        y2 = 534;
        x3 = 1675;
        y3 = 1939;
        x4 = 199;
        y4 = 1979;

        X1 = 0;
        Y1 = 0;
        X2 = 499;
        Y2 = 0;
        X3 = 499;
        Y3 = 499;
        X4 = 0;
        Y4 = 499;

        double M_a[][] = {
            {x1,y1,1,0,0,0,-x1*X1,-y1*X1},
            {x2,y2,1,0,0,0,-x2*X2,-y2*X2},
            {x3,y3,1,0,0,0,-x3*X3,-y3*X3},
            {x4,y4,1,0,0,0,-x4*X4,-y4*X4},
            {0,0,0,x1,y1,1,-x1*Y1,-y1*Y1},
            {0,0,0,x2,y2,1,-x2*Y2,-y2*Y2},
            {0,0,0,x3,y3,1,-x3*Y3,-y3*Y3},
            {0,0,0,x4,y4,1,-x4*Y4,-y4*Y4},
        };

        double M_b[][] = {
            {X1},
            {X2},
            {X3},
            {X4},
            {Y1},
            {Y2},
            {Y3},
            {Y4},
        };

        Matrix A = new Matrix(M_a);
        Matrix B = new Matrix(M_b);
        Matrix C = A.solve(B);
        double a = C.get(0, 0);
        double b = C.get(1, 0);
        double c = C.get(2, 0);
        double d = C.get(3, 0);
        double e = C.get(4, 0);
        double f = C.get(5, 0);
        double g = C.get(6, 0);
        double h = C.get(7, 0);


        int width = imgBuffer.getWidth();
        int height = imgBuffer.getHeight();

        BufferedImage output = new BufferedImage(500, 500, BufferedImage.TYPE_INT_RGB);
        int max = -5000;
        int min = 5000;
        for (int i = 0; i < width; i++) {
            for (int j = 0; j < height; j++) {
                if(isInside(i, j)){
                   int x = (int)(((a*i)+(b*j)+c)/((g*i)+(h*j)+1));
                   int y = (int)(((d*i)+(e*j)+f)/((g*i)+(h*j)+1));
                   if(y > max) max = y;
                   if(y < min) min = y;
                   int p = imgBuffer.getRGB(i, j);
                   output.setRGB(x, y, p);
                }

            }
        }
        System.out.println("max: " + max);
        System.out.println("min: " + min);
        File output1 = new File("C:\\Users\\mohar\\Desktop\\test\\bal.jpg");
        try {
            ImageIO.write(output, "jpg", output1);
        } catch (IOException ex) {
            Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
        }





    }

    public static boolean isInside(int x, int y){

        double apd = Math.abs(0.5 * (x1*y+x*y4+x4*y1-x*y1-x4*y-x1*y4));
        double dpc = Math.abs(0.5 * (x4*y+x*y3+x3*y4-x*y4-x3*y-x4*y3));
        double cpb = Math.abs(0.5 * (x3*y+x*y2+x2*y3-x*y3-x2*y-x3*y2));
        double pba = Math.abs(0.5 * (x*y2+x2*y1+x1*y-x2*y-x1*y2-x*y1));
        double rec = Math.abs(0.5 * (x1*y2+x2*y3+x3*y4+x4*y1-x2*y1-x3*y2-x4*y3-x1*y4));

        if((apd + dpc + cpb + pba) > rec){
            return false;
        }else{
            return true;
        }




    }