1al_lock_bitmap(3) al_lock_bitmap(3)
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6 al_lock_bitmap - Allegro 5 API
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9 #include <allegro5/allegro.h>
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11 ALLEGRO_LOCKED_REGION *al_lock_bitmap(ALLEGRO_BITMAP *bitmap,
12 int format, int flags)
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15 Lock an entire bitmap for reading or writing. If the bitmap is a dis‐
16 play bitmap it will be updated from system memory after the bitmap is
17 unlocked (unless locked read only). Returns NULL if the bitmap cannot
18 be locked, e.g. the bitmap was locked previously and not unlocked.
19 This function also returns NULL if the format is a compressed format.
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21 Flags are:
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23 · ALLEGRO_LOCK_READONLY - The locked region will not be written to.
24 This can be faster if the bitmap is a video texture, as it can be
25 discarded after the lock instead of uploaded back to the card.
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27 · ALLEGRO_LOCK_WRITEONLY - The locked region will not be read from.
28 This can be faster if the bitmap is a video texture, as no data need
29 to be read from the video card. You are required to fill in all pix‐
30 els before unlocking the bitmap again, so be careful when using this
31 flag.
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33 · ALLEGRO_LOCK_READWRITE - The locked region can be written to and read
34 from. Use this flag if a partial number of pixels need to be written
35 to, even if reading is not needed.
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37 format indicates the pixel format that the returned buffer will be in.
38 To lock in the same format as the bitmap stores its data internally,
39 call with al_get_bitmap_format(bitmap) as the format or use ALLE‐
40 GRO_PIXEL_FORMAT_ANY. Locking in the native format will usually be
41 faster. If the bitmap format is compressed, using ALLEGRO_PIXEL_FOR‐
42 MAT_ANY will choose an implementation defined non-compressed format.
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44 On some platforms, Allegro automatically backs up the contents of video
45 bitmaps because they may be occasionally lost (see discussion in
46 al_create_bitmap(3)'s documentation). If you're completely recreating
47 the bitmap contents often (e.g. every frame) then you will get much
48 better performance by creating the target bitmap with ALLEGRO_NO_PRE‐
49 SERVE_TEXTURE flag.
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51 Note: While a bitmap is locked, you can not use any drawing op‐
52 erations on it (with the sole exception of al_put_pixel(3) and
53 al_put_blended_pixel(3)).
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56 ALLEGRO_LOCKED_REGION(3), ALLEGRO_PIXEL_FORMAT(3), al_unlock_bitmap(3),
57 al_lock_bitmap_region(3), al_lock_bitmap_blocked(3), al_lock_bitmap_re‐
58 gion_blocked(3)
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62Allegro reference manual al_lock_bitmap(3)