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L_GetBitmapRow

Summary

Retrieves a row from a specified bitmap.The buffer to which pBuffer points should contain uncompressed data whether pBitmap is compressed or not.

Syntax

#include "l_bitmap.h"

L_LTKRN_API L_SSIZE_T L_GetBitmapRow(pBitmap, pBuffer, nRow, uBytes)

Parameters

pBITMAPHANDLE pBitmap

Pointer to the bitmap handle referencing the bitmap to get the row from.

L_UCHAR* pBuffer

Pointer to the buffer to hold the image data that this function gets. You must allocate the buffer before calling this function, and the buffer must be large enough to hold the image data. NOTE: The data in the buffer will be padded to pBitmap->BytesPerLine.

L_INT nRow

The number of the row to retrieve. The first row is 0, and the last row is 1 less than the bitmap height.

L_SIZE_T uBytes

The number of bytes in the row to retrieve. To get a full row, use the value in the BytesPerLine field in the bitmap handle. When getting less than full row, you must consider the bits per pixel.

Value	Meaning
1-bit bitmap	Each byte represents 8 pixels.
4-bit bitmap	Each byte represents 2 pixels.
8-bit bitmap	Each byte represents 1 pixel.
16-bit bitmap	Every 2 bytes represents one pixel.
24-bit bitmap	Every three bytes represents one pixel.
32-bit bitmap	Every four bytes represents one pixel.
48-bit bitmap	Every six bytes represents one pixel.
64-bit bitmap	Every eight bytes represents one pixel.

You can use the bitmap handle's BitsPerPixel field with integer math to calculate the number of bytes needed for a particular number of pixels. For example:

NumberOfBytes = (Bitmap.BitsPerPixel * NumberOfPixels) / 8; 
if ((Bitmap.BitsPerPixel * NumberOfPixels) % 8) 
   ++NumberOfBytes; /* Round up if necessary for a 1- or 4-bit image */

Returns

Value	Meaning
>=1	The number of bytes copied.
< 1	An error occurred. Refer to Return Codes.

Comments

This function copies image data from the bitmap to a buffer that you specify. The data is copied exactly as it is stored in the image. The bitmap memory must be locked when you use this function. Normally, you can call L_AccessBitmap to lock the memory before starting an operation that uses this function, then call L_ReleaseBitmap when the operation is finished.

Use the BytesPerLine field in the bitmap handle to determine the byte count of each line. Color order is determined by the Order field in the bitmap handle. This value can be ORDER_RGB, ORDER_BGR, ORDER_GRAY or ORDER_ROMM. ORDER_GRAY is only valid for 12-, 16-, and 32-bit grayscale images. Support for 12-, 16-, and 32-bit grayscale images is only available in the Document and Medical Imaging toolkits.

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

Win32, x64, Linux.

Example

For complete sample code, refer to the GETROW
example.
This example gets each row from a bitmap, inverts the color values, and puts the row back into the bitmap.

L_INT GetBitmapRowExample(L_VOID) 
{ 
   L_INT nRet; 
   BITMAPHANDLE   LeadBitmap;   /* Bitmap handle to hold the loaded image */ 
   L_UCHAR*       pBuf;         /* Buffer to hold the row */ 
   HGLOBAL        hBuf;         /* Handle to the buffer */ 
   L_INT          nRow;         /* Row counter */ 
   L_UINT         uByte;        /* Byte counter */ 
 
   /* Load the bitmap, at 24 bits per pixel */ 
   nRet = L_LoadBitmap (MAKE_IMAGE_PATH(TEXT("ImageProcessingDemo\\Image3.cmp")), &LeadBitmap, sizeof(BITMAPHANDLE), 24, ORDER_BGR, NULL, NULL); 
   if(nRet != SUCCESS) 
      return nRet; 
   /* Allocate and lock the buffer */ 
   hBuf = GlobalAlloc(GMEM_MOVEABLE,LeadBitmap.BytesPerLine); 
   pBuf = (L_UCHAR *)GlobalLock( hBuf ); 
   /* Process each row in the bitmap */ 
   L_AccessBitmap(&LeadBitmap); 
   for(nRow = 0; nRow < LeadBitmap.Height; nRow++) 
   { 
      nRet =(L_INT) L_GetBitmapRow(&LeadBitmap, pBuf, nRow, LeadBitmap.BytesPerLine); 
      if(nRet < 1) 
         return nRet; 
      for(uByte = 0; uByte < LeadBitmap.BytesPerLine; uByte++) 
         pBuf[uByte] ^= 0xFF; 
      nRet = (L_INT )L_PutBitmapRow(&LeadBitmap, pBuf, nRow, LeadBitmap.BytesPerLine); 
      if(nRet <1) 
         return nRet; 
   } 
   L_ReleaseBitmap(&LeadBitmap); 
 
   nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("Result.BMP")), &LeadBitmap, FILE_BMP, 24, 0, NULL); 
   if(nRet != SUCCESS) 
      return nRet; 
   L_FreeBitmap(&LeadBitmap); 
 
   /* Free memory that we no longer need */ 
   GlobalUnlock(hBuf); 
   GlobalFree(hBuf); 
   return SUCCESS; 
}