计算0度的灰度共阵

Question

//计算0度的灰度共生阵
for(i=0; i<LocalImageWidth; i++)
{
for(j=0; j<LocalImageWidth-distance; j++)
       {
      PMatrixH[(unsigned int)NewImage[i][j]][(unsigned int)NewImage[i][j+distance]] += 1;
      PMatrixH[(unsigned int)NewImage[i][j+distance]][(unsigned int)NewImage[i][j]] += 1;
      }
}
distance为距离，请问 PMatrixH[(unsigned int)NewImage[i][j]][(unsigned int)NewImage[i][j+distance]] += 1;怎么理解