Arrays: Counting, Comparing and Increase

Question

Woohoo, I've come to arrays now, thank god.

Now, I've got 2 arrays!

int colorvalues[][]  = {{34,255,255,56},{127,204,11,34},{123,98,127,34},{34,34,127,17}};

Imagine it as a 4x4 pixel picture

Now, I want to create a histogram, the distribution of colorvalues from 0 to 255. For example here I've 2*255, 2*127, 5*34 and so on.

So I've created an int histogram[] = new int [255];

To test if my colorvalues are correct I wrote:

 for(int i=0; i < colorvalues.length; i++){
  for (int j = 0; j < colorvalues.length; j++){
   System.out.println("Colorvalue in Array " + i + "." + j + " is" + colorvalues[i][j]);
  }
 }

So far, so good. Now, how do I write a procedure that goes in histogram[255] from 0 to 255, and compares it to the value of colorvalues[][], and if, for example, histogram[34] compares to colorvalues[][] it adds 5 to histogram[34]. Because there's 5 times 34 in colorvalues[][].

Maybe my thinking is wrong and I was supposed to have histogram[255][], 255 for colorvalues from 0 to 255 and the other for the counter. Even then, how do I realize it?

Answer 1

I'd be tempted to add the histogram values into a TreeMap where the map key is the colour value and the map value is the count.

The map will increase in size automatically, no problems with index out of bounds etc. it will be sorted automatically into size order.