for(i = 1; i+1<h; i++) {
            for(j = 1; j+1<w; j++) {

                tl = (i >= roi.y && j >= roi.x);
                br = (i <= roi.y+roi.height && j <= roi.x+roi.width);

                if(tl && br) {
                    //(1   2  1)
                    //(0   0  0)
                    //(-1 -2 -1)

                    //(1 0 -1)
                    //(2 0 -2)
                    //(1 0 -1)

                    index = (i*w)+j;
                    indexOL = ((i-1)*w)+j-1;
                    indexO = ((i-1)*w)+j;
                    indexOR = ((i-1)*w)+j+1;
                    indexL = (i*w)+j-1;
                    indexR = (i*w)+j+1;
                    indexUL = ((i+1)*w)+j-1;
                    indexU = ((i+1)*w)+j;
                    indexUR = ((i+1)*w)+j+1;

                    int pxOL = (int) pixelsin[indexOL]&0xff;
                    int pxO  = (int) pixelsin[indexO]&0xff;
                    int pxOR = (int) pixelsin[indexOR]&0xff;
                    int pxL  = (int) pixelsin[indexL]&0xff;
                    int px   = (int) pixelsin[index]&0xff;
                    int pxR  = (int) pixelsin[indexR]&0xff;
                    int pxUL = (int) pixelsin[indexUL]&0xff;
                    int pxU  = (int) pixelsin[indexU]&0xff;
                    int pxUR = (int) pixelsin[indexUR]&0xff;

                    wert = (1*pxOL + 2*pxO + 1*pxOR + -1*pxUL + -2*pxU + -1*pxUR) + 127;

                    if(wert < 0) {
                        wert = 0;
                    } else if(wert > 255) {
                        wert = 255;
                    }

                    pixels[index] = (byte)wert;
                }
            }
        }