image[x * (j + 2) + i + 1] + image[x * (j + 2) + i + 2] +
image[x * (j + 1) + i - 2] + image[x * (j + 1) + i - 1] + image[x * (j + 1) + i] +
image[x * (j + 1) + i + 1] + image[x * (j + 1) + i + 2]
- - (25 * image[x * j + i]);
+ - (24 * image[x * j + i]);
if (sum < 0) sum = 0;
if (sum > 255) sum = 255;
n_image[x * j + i] = sum;