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Al create sub bitmap
al_create_sub_bitmap - creates a sub-bitmap from a parent
AL_BITMAP *al_create_sub_bitmap(AL_BITMAP *parent, int x, int y, int w, int h)
|parent||The parent bitmap|
|x, y||The top left position of the sub-bitmap within the parent bitmap|
|w, h||The width and height of the sub-bitmap|
Creates a sub-bitmap of the parent, at the specified coordinates and of the specified size. A sub-bitmap is a bitmap that shares drawing memory with a pre-existing (parent) bitmap, but possibly with a different size and clipping settings.
When creating a sub-bitmap of a mode-X display bitmap, the x position must be a multiple of four.
If the sub-bitmap does not lie completely inside the parent bitmap, then it is automatically clipped so that it does.
The parent bitmap's clipping rectangles are ignored.
Destroying parents of sub-bitmaps will not destroy the sub-bitmaps; instead the sub-bitmaps become invalid and should no longer be used.
If a sub-bitmap was not or cannot be created then NULL is returned.