Manual Reference Pages - AL_LOCK_BITMAP (3)
al_lock_bitmap - Allegro 5 API
ALLEGRO_LOCKED_REGION *al_lock_bitmap(ALLEGRO_BITMAP *bitmap,
int format, int flags)
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.
[aq]format[aq] indicates the pixel format that the returned buffer
will be in.
To lock in the same format as the bitmap stores it[aq]s data
internally, call with C]al_get_bitmap_format(bitmap)] as the
format or use ALLEGRO_PIXEL_FORMAT_ANY.
Locking in the native format will usually be faster.
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
Use this flag if a partial number of pixels need to be written to, even
if reading is not needed.
I]Note:] While a bitmap is locked, you can not use any drawing
operations on it (with the sole exception of al_put_pixel(3) and
ALLEGRO_LOCKED_REGION(3), ALLEGRO_PIXEL_FORMAT(3), al_unlock_bitmap(3)
|Allegro reference manual ||AL_LOCK_BITMAP (3) || |
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