Tukukkk

Yet again im in trouble. I'm using an sobel edgedetector to get the edge of an image. Im using bresenhams algorithm to draw on the other end. But for that to happen i need solid coordinates.

My sobel returns 2 0's for each edge, and i just cant figure out why. If the image was twice as large it would make sense, but it is not.

In PAINT i made a 50x50 pixel image of a singe pixel square, that returns a 48x48 int array looking like this. the 48x48 i understand, but the 2 0's i do not understand.

255 255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255 255
255 255 255 0 0 0 0 0 0 0 0
255 255 255 0 0 0 0 0 0 0 0
255 255 255 0 0 255 255 255 255 255 255
255 255 255 0 0 255 255 255 255 255 255
255 255 255 0 0 255 255 255 255 255 255
255 255 255 0 0 255 255 255 255 255 255
255 255 255 0 0 255 255 255 255 255 255

the sobel i use comes from a method called magnitude array

public int getMagnitudeArray() {



   int filter1 = {

        {-1, 0, 1},

        {-2, 0, 2},

        {-1, 0, 1}

    };



    int filter2 = {

        {1, 2, 1},

        {0, 0, 0},

        {-1, -2, -1}

    };



    Picture picture0 = new Picture(imagePath);

    int width = picture0.width()-2;

    int height = picture0.height()-2;

    int arrayRepresentation = new int[width][height];



    for (int y = 0; y < height ; y++) {

        for (int x = 0; x < width ; x++) {



            // get 3-by-3 array of colors in neighborhood

            int gray = new int[3][3];

            for (int i = 0; i < 3; i++) {

                for (int j = 0; j < 3; j++) {

                    gray[i][j] = (int) Luminance.intensity(picture0.get(x + i, y + j));

                }

            }



            // apply filter

            int gray1 = 0, gray2 = 0;

            for (int i = 0; i < 3; i++) {

                for (int j = 0; j < 3; j++) {

                    gray1 += gray[i][j] * filter1[i][j];

                    gray2 += gray[i][j] * filter2[i][j];

                }

            }

            // int magnitude = 255 - truncate(Math.abs(gray1) + Math.abs(gray2));

            int magnitude = 255 - binaryTruncate((int) Math.sqrt(gray1 * gray1 + gray2 * gray2));

            arrayRepresentation[x][y] = magnitude;

        }

    }



    return arrayRepresentation;

} `

Is there anyone who can tell me why this method returns 2 0's and how i change it to return only 1, 0?

I tried to "fix" it after it returns the array with a hell og a lot of if statements, but it does not seem very elegant og efficiant.

Thanks.