Unit 'agraphics'	Package
[Overview][Constants][Types][Procedures and functions][Variables][Index]	[#amunits]

AllocBitMap

Allocate a bitmap and attach bitplanes to it.

Declaration

Source position: agraphics.pas line 2257

function AllocBitMap(

sizex: LongWord;

sizey: LongWord;

depth: LongWord;

flags: LongWord;

const friend_bitmap: pBitMap

):pBitMap;

Arguments

`sizex`		The width (in pixels) desired for the bitmap data.
`sizey`		The height (in pixels) desired.
`depth`		The number of bitplanes deep for the allocation. Pixels with at least this many bits will be allocated.
`flags`		Flags for Bitmap creation (BMF_*)
`friend_bitmap`		Pointer to another bitmap, or `nil`. If this pointer is passed, then the bitmap data will be allocated in the most efficient form for blitting to `friend_bitmap`.

Description

Allocates and initializes a bitmap structure. Allocates and initializes bitplane data, and sets the bitmap's planes to point to it.

BMF_CLEAR: to specify that the allocated raster should be filled with color 0.
BMF_DISPLAYABLE: to specify that this bitmap data should be allocated in such a manner that it can be displayed. Displayable data has more severe alignment restrictions than non-displayable data in some systems.
BMF_INTERLEAVED: tells graphics that you would like your bitmap to be allocated with one large chunk of display memory for all bitplanes. This minimizes color flashing on deep displays. If there is not enough contiguous RAM for an interleaved bitmap, graphics.library will fall back to a non-interleaved one.
BMF_MINPLANES: causes graphics to only allocate enough space in the bitmap structure for "depth" plane pointers. This is for system use and should not be used by applications use as it is inefficient, and may waste memory.

NOTE:

When allocating using a friend bitmap, it is not safe to assume anything about the structure of the bitmap data if that friend BitMap might not be a standard amiga bitmap (for instance, if the workbench is running on a non-amiga display device, its Screen^.RastPort^.BitMap won't be in standard amiga format. The only safe operations to perform on a non-standard BitMap are:

blitting it to another bitmap, which must be either a standard Amiga bitmap, or a friend of this bitmap.
blitting from this bitmap to a friend bitmap or to a standard Amiga bitmap.
attaching it to a rastport and making rendering calls.

Good arguments to pass for the friend_bitmap are your window's RPort^.BitMap, and your screen's RastPort^.BitMap. Do not pass @(screenptr^.BitMap)!

BitMaps not allocated with BMF_DISPLAYABLE may not be used as Intuition Custom BitMaps or as RasInfo^.BitMaps. They may be blitted to a BMF_DISPLAYABLE BitMap, using one of the BltBitMap() family of functions.

AllocBitMap

Declaration

Arguments

Description

See also