this code is to perform LocalColorHistogram.But i can't understand it

public Vector<Double> getFeatureVector(int[] inImg, int height, int width, int[] maskImg, int flag, double feature, int featureDimension) { int gridCount = 4; int row = gridCount * gridCount; Vector<Double> localColorHistogram = new Vector<Double>(row * 64); int size = width * height; int i = 0; int j = 0; int k = 0; double[][] histogram = new double[row][64];

    for(i=0 ; i<row ; i++){
        histogram[i] = new double[64];
        for(j=0 ; j<64 ; j++){
            histogram[i][j] = 0.0d;
        }
    }
    for(i=0 ; i<size ; i++){
        k = (inImg[i]>>18 & 0x30) | (inImg[i]>>12 & 0xc) | (inImg[i]>>6 & 0x3);
        j = getGrid(i, width, height, gridCount);
        histogram[j][k] += 1.0;
    }
    for(i=0 ; i<gridCount ; i++)
        for(j=0 ; j<64 ; j++)
            localColorHistogram.add(round(((double)histogram[i][j]/(size/gridCount))));
    histogram = null;
    return localColorHistogram;

}
private int getGrid(double j, double width, double height, int gridCount){
    double localWidth = width/gridCount;
    double localHeight = height/gridCount;
    int cell = (int)(j/width/localHeight)*gridCount + (int)((j % width)/localWidth);
    return cell;
}