trusty (3) al_lock_bitmap.3alleg5.gz

NAME

       al_lock_bitmap - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro.h>

              ALLEGRO_LOCKED_REGION *al_lock_bitmap(ALLEGRO_BITMAP *bitmap,
                 int format, int flags)

DESCRIPTION

       Lock  an entire bitmap for reading or writing.  If the bitmap is a display bitmap it will be updated from
       system memory after the bitmap is unlocked (unless locked read only).  Returns NULL if the bitmap  cannot
       be locked, e.g.  the bitmap was locked previously and not unlocked.

       Flags are:

       • ALLEGRO_LOCK_READONLY  - The locked region will not be written to.  This can be faster if the bitmap is
         a video texture, as it can be discarded after the lock instead of uploaded back to the card.

       • ALLEGRO_LOCK_WRITEONLY - The locked region will not be read from.  This can be faster if the bitmap  is
         a  video  texture,  as  no  data  need to be read from the video card.  You are required to fill in all
         pixels before unlocking the bitmap again, so be careful when using this flag.

       • ALLEGRO_LOCK_READWRITE - The locked region can be written to and read from.  Use this flag if a partial
         number of pixels need to be written to, even if reading is not needed.

       'format'  indicates  the pixel format that the returned buffer will be in.  To lock in the same format as
       the bitmap stores it's data internally, call with  al_get_bitmap_format(bitmap)  as  the  format  or  use
       ALLEGRO_PIXEL_FORMAT_ANY.  Locking in the native format will usually be faster.

              Note:  While  a  bitmap  is  locked,  you  can not use any drawing operations on it (with the sole
              exception of al_put_pixel(3alleg5) and al_put_blended_pixel(3alleg5)).

SEE ALSO

       ALLEGRO_LOCKED_REGION(3alleg5), ALLEGRO_PIXEL_FORMAT(3alleg5), al_unlock_bitmap(3alleg5)