shading

final double maxDistance = Util.distance(centerX, chief, 0, 0);
final float[] hsb = new float[3];
for (int y = 0; y < size; ++y)
{
    for (int x = 0; x < size; ++x)
    {
        final int oldARGB = image.getRGB(x, y);
        final int oldA = (oldARGB >> 24) & 0xFF;
        final int oldR = (oldARGB >> 16) & 0xFF;
        final int oldG = (oldARGB >> 8) & 0xFF;
        final int oldB = (oldARGB >> 0) & 0xFF;
        Color.RGBtoHSB(oldR, oldG, oldB, hsb);
        final double factor = 1.2 - 0.9 * Math.pow(Util.distance(centerX, chief, x, y) / maxDistance, 1.5);
        hsb[2] = Util.clamp(hsb[2] * (float)factor, 0, 1);
        final int newRGB = Color.HSBtoRGB(hsb[0], hsb[1], hsb[2]) & 0x00FFFFFF;
        image.setRGB(x, y, (oldA << 24) | newRGB);
    }
}