Thanks for replies.

so the evaulation of that statement   r = pSrc8[0] + pSrc8[4] + pSrc8[stride+0] + pSrc8[stride+4];

is :    r = first red byte + 4th red byte of 4th pixel, red byte at row 800  and red byte 404 at row 800 ?

Thanks for replies.

so the evaulation of that statement   r = pSrc8[0] + pSrc8[4] + pSrc8[stride+0] + pSrc8[stride+4];

is :    r = first pixel + 4th pixel, pixel 400 at row 800  and pixel 404 at row 800 ?