HISTO_STEP_SIZE    55 core/autoiso.c     int total = ((vp_width + HISTO_STEP_SIZE/2)/HISTO_STEP_SIZE) * vp_height;
HISTO_STEP_SIZE    68 core/autoiso.c             for (x=HISTO_STEP_SIZE/2; x<vp_width; x+=HISTO_STEP_SIZE)