Apart from the randomness missing, I don't see any question, so I assume that it's about this:
public static short[][] brighten(short[][] orig, short amount) {
Random random = new Random();
short[][] returnArray = new short[orig.length][orig[0].length];
for(int i = 0; i < orig.length; ++i){
for(int j = 0; j < orig[0].length; ++j){
int randomValue = -amount + random.nextInt(amount+amount);
returnArray[i][j] = (short)(orig[i][j]+randomValue);
}
}
return returnArray;
}