Question

I try to create a program which computes image histogram. I ve got the above code but i cant figure out why it doesnt work.

    public void hist(List<Integer> r, List g, List b){

    int count[] = new int [256];

    int rSize = r.size();
    int gSize = g.size();
    int bSize = b.size();


    for (int j = 0; j<=255; j++){

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

        if( r.get(i) ==  j ){}

            //System.out.println(r.get(i) ==  j);

            count[j]++;

        }
    }

    for (int i = 0; i < count.length; i++) {

        System.out.print(count[i]);

    }
}

If i call it in main, every element of count is rSize which is impossible as r list has the values of Red channel of an image.

Answer 1

Your if is empty: if( r.get(i) == j ){}.

It should be:

if( r.get(i) ==  j )
{
    count[j]++;
}

Might want to use the debugger next time and simply step through your code, would’ve caught this easily.