L_GetBitmapRowCompressed

#include "l_bitmap.h"

L_INT EXT_FUNCTION L_GetBitmapRowCompressed(pBitmap, pWorkBuffer, pRunBuffer, nRow, nLines)

pBITMAPHANDLE pBitmap;	/* pointer to the bitmap handle */
L_UCHAR L_FAR * pWorkBuffer;	/* pointer to a work buffer */
L_UINT16 L_FAR * pRunBuffer;	/* pointer to the target buffer */
L_UINT nRow;	/* number of the first row to retrieve */
L_UINT nLines;	/* number of the rows to retrieve */

Retrieves one or more rows of 1-bit compressed data from a bitmap that has been loaded in its compressed format. This function is available in the Document/Medical Toolkits.

Parameter	Description
pBitmap	Pointer to the bitmap handle referencing the bitmap to get the data from.
pWorkBuffer	NULL or a pointer to an optional work buffer. Allocating the work buffer speeds processing if you call this function more than once, because if you do not allocate a work buffer, the function allocates and frees a temporary buffer each time it is called. The size of this buffer should be the same as the bitmap handle's BytesPerLine field.
pRunBuffer	Pointer to the output buffer, which will be filled with 1-bit compressed image data. Calculate the required size of this buffer as follows: bytes required = nLines * ((bitmap width + 3) * 2).
nRow	Number of the first row to retrieve.
nLines	Number of rows to retrieve.

Returns

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

Comments

This function is useful for working with 1-bit images that are loaded in their compressed formats for faster loading and display. For more information, refer to Speeding Up 1-Bit Documents.

Required DLLs and Libraries

LTKRN

For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

Platforms

Windows 95 / 98 / Me, Windows 2000 / XP, Windows CE.

See Also

Functions:	L_ExpandRow, L_CompressRow, L_GetBitmapRowColCompressed, L_PutBitmapRowColCompressed, L_PutBitmapRowCompressed
Topics:	Speeding Up 1-Bit Documents

Example

The following example is designed to work with bitmaps that have a bottom-left or top-left view perspective:

/* This example demonstrates the low-level functions for accessing
1-bit compressed bitmap data. It demonstrates the ability to get and put
rows, and the ability to process rows in buffer-to-buffer processing.
The result of the function is an the first 50 lines are inverted. */

void TestLoad(L_TCHAR L_FAR * pszFilename, HWND hWnd)
{
   BITMAPHANDLE LeadBitmap;   /* Bitmap handle for the image */
   L_UCHAR L_HUGE * pBuffer;  /* Buffer to hold the expanded row */
   L_UINT16 L_HUGE * pRunBuffer; /* Buffer to hold the compressed row */
   HGLOBAL hBuffer;           /* Handle to the pBuffer */
   HGLOBAL hRunBuffer;        /* Handle to the pRunBuffer */
   L_INT n;                   /* Counters */
   L_INT nRow = 0;            /* first row to get */
   L_INT nYSize = 50;         /* # of rows to get */
   L_INT nRet;
   /* Load the bitmap, as compressed */
   nRet = L_LoadFile(pszFilename,&LeadBitmap, sizeof(BITMAPHANDLE),1,0,
               LOADFILE_COMPRESSED | LOADFILE_ALLOCATE | LOADFILE_STORE,
               NULL, NULL, NULL, NULL);
   /* if the ViewPerspective is not TOP_LEFT or BOTTOM_LEFT, make it TOP_LEFT */
   /* Get/PutRow functions only work with TOP_LEFT or BOTTOM_LEFT */
   if ( (LeadBitmap.ViewPerspective != TOP_LEFT)
      || (LeadBitmap.ViewPerspective != BOTTOM_LEFT) )
      L_ChangeBitmapViewPerspective ( NULL, &LeadBitmap, sizeof(BITMAPHANDLE), TOP_LEFT );
   if (LeadBitmap.ViewPerspective == BOTTOM_LEFT)
   {
      nRow = LeadBitmap.Height - nRow - nYSize;
   }
   /* Allocate the buffers */
   hBuffer = GlobalAlloc(GMEM_MOVEABLE, (((LeadBitmap.Width + 31) &~31)/ 8) * nYSize);
   pBuffer = (L_UCHAR L_FAR *)GlobalLock( hBuffer );
   hRunBuffer = GlobalAlloc (GMEM_MOVEABLE, (L_UINT32)((LeadBitmap.Width + 3) * 2) * nYSize);
   pRunBuffer = (L_UINT16 L_HUGE *)GlobalLock (hRunBuffer);
   /* Access the bitmap */
   L_AccessBitmap(&LeadBitmap);
   /* Get the top nRow lines */
   L_GetBitmapRowCompressed ( &LeadBitmap, NULL, pRunBuffer, nRow, nYSize );
   /* Expand the compressed data */
   L_ExpandRows( pRunBuffer, pBuffer, LeadBitmap.Width, nYSize);
   /* Invert the data */
   for(n=0; n < (L_INT)LeadBitmap.BytesPerLine * nYSize; n++)
      pBuffer[n] = pBuffer[n] ^ 0xFF;
   /* Compress the inverted data */
   L_CompressRows( pRunBuffer, pBuffer, LeadBitmap.Width, nYSize);
   /* Put the inverted, compressed data back into the bitmap */
   L_PutBitmapRowCompressed ( &LeadBitmap, NULL, pRunBuffer, nRow, nYSize );
   L_ReleaseBitmap(&LeadBitmap);
   /* Free memory that we no longer need */
   GlobalFree(hBuffer);
   GlobalFree(hRunBuffer);
}