class PpeOp extends Operator {

    static double[] getPixelList(int x, int y, Tile sourceTile) {
        double[] pixelList = new double[5];
        pixelList[0] = getPixelValue(sourceTile, x, y - 2);
        pixelList[1] = getPixelValue(sourceTile, x, y - 1);
        pixelList[2] = getPixelValue(sourceTile, x, y);
        pixelList[3] = getPixelValue(sourceTile, x, y + 1);
        pixelList[4] = getPixelValue(sourceTile, x, y + 2);
        Arrays.sort(pixelList);
        if (pixelList[0] < 0) {
            throw new OperatorException("Radiance bands contain values lower than zero at x=" + x + " y=" + y);
        }
        return pixelList;
    }

}