docs: private void calc(int x, int y) {
          double d;
          int dIndex;
          int index;
  
          for (int alpha = 0; alpha < (this.cSteps - 1); alpha++) {
              d = y * this.cCosA[alpha] - x * this.cSinA[alpha];
              dIndex = (int) (d - this.cDMin);
              index = dIndex * this.cSteps + alpha;
              try {
                  this.cHMatrix[index] += 1;
              } catch (Exception e) {
                  logger.warn("", e);
              }
          }
      }