L_SetMemoryThresholds

#include "l_bitmap.h"

L_LTKRN_API L_INT L_SetMemoryThresholds(nTiledThreshold, nMaxConvSize, nTileSize, nConvTiles, nConvBuffers, uFlags);

Sets the memory restrictions for allocating bitmaps.

Parameters

L_INT nTiledThreshold

Minimum amount of free memory required to allow the allocation of conventional bitmaps (default 0). If the amount of free memory falls below this threshold, all bitmaps will be allocated as tiled. The exception is when the bitmap size is smaller than the tile size in this case, the bitmap will be allocated in conventional memory.

Values less than 100 are not allowed.

If this parameter is:

This parameter is ignored if uFlags does not contain MEM_TILEDTHRESHOLD.

L_SSIZE_T nMaxConvSize

Maximum size for a conventional bitmap (default is 0x7FFFFFFF). Any bitmaps with a size bigger than this will be allocated as tiled.

If this parameter is:

Values less than 100 are not allowed.

This parameter is ignored if uFlags does not contain MEM_MAXCONVSIZE.

L_SSIZE_T nTileSize

The size of the tile for tiled bitmaps (default 0). Pass a value smaller than nMaxConvSize.

All bitmaps with a size smaller than nTileSize will be allocated as conventional. (A tiled bitmap of a size smaller than nTileSize would consist of only small tile, which is the equivalent of the conventional bitmap).

If nTileSize is 0, then LEADTOOLS will pick a default size for the tile. (Currently it is 16MB)

The tiles will be smaller than this value and will be a complete number of rows. No rows will be split between tiles.

Values less than 0 are not allowed.

This parameter is ignored if uFlags does not contain MEM_TILESIZE.

L_INT nConvTiles

This is used when working with a tiled image. It represents the maximum number of tiles that will reside in conventional memory at any time. The tiles that do not reside in conventional memory will be on disk. (Default is 100 = all tiles are in memory)

If the value is:

Values less than -100 are not allowed.

This parameter is ignored if uFlags does not contain MEM_CONVTILES.

L_INT nConvBuffers

This is used when working with tiled images which have disk tiles. It represents the number of buffers in conventional memory that will cache the disk tiles. The swap buffers will greatly improve the access to these disk tiles. The default is 1 (one swap buffer will be used to cache the disk tiles).

This parameter specifies how many buffers should be used:

It is useful to have more than one swap buffer when you have an algorithm that constantly reads data going up and down. Usually, the data is read in one direction (from top to bottom or bottom to top) in this case, one swap buffer will be enough. Also, if you only view a certain portion of the image, you might benefit from having enough swap buffers to cache the visible portion of the image (or the bitmaps region).

The buffers are dynamic: when data is being read/written to a disk tile, a cache buffer is created (if permitted and there is enough memory). If the maximum number of cache buffers for that bitmap has been reached, the cache buffer for the last used tile will be deleted and used for the new tile.

L_UINT uFlags

A combination of flags that indicates which of the threshold parameters are valid. The flags can be or-ed together to change only some of the flags, or you can pass MEM_ALL to change all flags. Possible values are:

Value Meaning
MEM_TILEDTHRESHOLD [0x0001] nTiledThreshold is valid.
MEM_MAXCONVSIZE [0x0002] nMaxConvSize is valid
MEM_TILESIZE [0x0004] nTileSize is valid
MEM_CONVTILES [0x0008] nConvTiles is valid
MEM_CONVBUFFERS [0x0010] nConvBuffers is valid.
MEM_ALL [0x001F] all parameters are valid. You do not need to or this with the other flags

Returns

Value Meaning
SUCCESS The function was successful.
< 1 An error occurred. Refer to Return Codes.

Comments

These are global settings and apply to the current thread. They will apply to bitmaps created in this thread after this function is called.

Required DLLs and Libraries

Platforms

Win32, x64, Linux.

See Also

Functions

Topics

Example

L_INT SetMemoryThresholdsExample(L_VOID) 
{ 
   L_INT nRet; 
   /* Allocate tiled bitmaps when more than 75% of the computer memory is used, or for bitmaps larger than 100MB. */ 
   nRet = L_SetMemoryThresholds(-25, 100 *1024 * 1024, 0, 0, 0, MEM_TILEDTHRESHOLD | MEM_MAXCONVSIZE); 
   if(nRet != SUCCESS) 
      return nRet; 
   return SUCCESS; 
} 
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