This fixes the calculation of the number of needed blocks to make
sure that ALL pixels are represented by the result.
Reviewed-by: Thomas Volkert <silvo@gmx.net>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 7f64a750)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>