L_ChangeBitmapHeight

#include "l_bitmap.h"

L_LTKRN_API L_INT L_ChangeBitmapHeight(pBitmap, nHeight)

Increases or decreases the allocated height of a bitmap. You can use this function in a callback routine to adjust the allocation when loading an image of unknown height.

Parameters

pBITMAPHANDLE pBitmap

Pointer to the bitmap handle referencing the bitmap to be adjusted.

L_INT nHeight

New height in pixels.

Returns

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

Comments

This function updates the fields in the bitmap handle to reflect the change.

Required DLLs and Libraries

Platforms

Win32, x64, Linux.

See Also

Functions

Topics

Example

This FILEREADCALLBACK example uses L_ChangeBitmapHeight to ensure that the final bitmap height is the same as the total number of loaded lines. This can be especially useful when you are loading fax files and you don’t know how many lines are in the file. Normally, you know the width of the raw fax files but not the height. So you can start by allocating a small bitmap and increase its height while decoding the file.

L_UINT TotalLines; /* Total number of loaded lines */ 
 
L_INT EXT_CALLBACK LoadImageCB(pFILEINFO        pFileInfo, 
                               pBITMAPHANDLE    pBitmap, 
                               L_UCHAR*         pBuffer, 
                               L_UINT           uFlags, 
                               L_INT            nRow, 
                               L_INT            nLines, 
                               L_VOID*          pUserData ) 
{ 
   UNREFERENCED_PARAMETER(pFileInfo); 
   UNREFERENCED_PARAMETER(pBuffer); 
   UNREFERENCED_PARAMETER(uFlags); 
   UNREFERENCED_PARAMETER(nRow); 
   UNREFERENCED_PARAMETER(pBitmap); 
   BITMAPHANDLE *pMyBitmap = (BITMAPHANDLE*)pUserData; 
 
   /* Increment the current row by the number of lines in the buffer */ 
   TotalLines += nLines; 
   /* Set the bitmap height to the total number of lines */ 
   L_AccessBitmap(pMyBitmap); 
   if( TotalLines > (L_UINT)pMyBitmap->Height ) 
   { 
      L_ReleaseBitmap(pMyBitmap); 
      L_ChangeBitmapHeight(pMyBitmap, TotalLines ); 
      L_AccessBitmap(pMyBitmap); 
   } 
   L_PutBitmapRow(pMyBitmap, pBuffer, nRow, pMyBitmap->BytesPerLine * nLines); 
   L_ReleaseBitmap(pMyBitmap); 
   return( SUCCESS ); 
} 
 
L_INT ChangeBitmapHeightExample(L_VOID) 
{ 
   L_INT nRet; 
   BITMAPHANDLE LeadBitmap; 
   BITMAPHANDLE DummyBitmap; 
   FILEINFO FileInfo; 
 
   memset(&FileInfo, 0, sizeof(FILEINFO)); 
   nRet = L_FileInfo(MAKE_IMAGE_PATH(TEXT("OCR1.TIF")), &FileInfo, sizeof(FILEINFO), 0, NULL); 
   if(nRet != SUCCESS) 
      return nRet; 
   /* init and allocate the bitmap, to be 1/2 the actual size of the image */ 
   L_InitBitmap(&LeadBitmap, sizeof(BITMAPHANDLE), FileInfo.Width, FileInfo.Height / 2, FileInfo.BitsPerPixel); 
   L_AllocateBitmap(&LeadBitmap, TYPE_CONV); 
 
   nRet = L_LoadFile(MAKE_IMAGE_PATH(TEXT("OCR1.TIF")), &DummyBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, 0, LoadImageCB, (L_VOID*)&LeadBitmap, NULL, NULL); 
   if(nRet != SUCCESS) 
      return nRet; 
 
   L_FreeBitmap(&LeadBitmap); 
   L_FreeBitmap(&DummyBitmap); 
 
   return nRet; 
} 

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