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L_GrayScaleBitmap

Summary

Converts a 1-, 4-, 8-, 16-, 24-, or 32-bit bitmap to an 8-bit, 12-bit, 16-bit, or 32-bit grayscale bitmap. Support for 12, 16 and 32-bit grayscale images is available in the Document and Medical Imaging toolkits.

Syntax

#include "l_bitmap.h"

L_LTKRN_API L_INT L_GrayScaleBitmap(pBitmap, nBitsPerPixel)

Parameters

pBITMAPHANDLE pBitmap

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

L_INT nBitsPerPixel

Value indicating the number of bits in the destination bitmap. Valid values are 8, 12, 16, or 32.

Returns

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

Comments

The resulting bitmap can be an 8-bit, 12-bit, 16-bit or 32-bit grayscale bitmap. Once the function is complete, the Order member of the bitmap handle is set to ORDER_GRAY.

When converting to 12-bit, 16-bit or 32-bit grayscale, a Lookup table is not used. When converting to 8-bit grayscale, a Lookup table is used to get the RGB for each input pixel. The grayscale value corresponding to that RGB triple is used in the destination bitmap.

To update a status bar or detect a user interrupt during execution of this function, refer to L_SetStatusCallback.

L_GrayScaleBitmap is one of the few functions that can operate on bitmap with floating point pixels. It will convert such a bitmap to a bitmap with integer pixel values so you can use the rest of the LEADTOOLS functions. But note that this conversion will scale the floating values and convert them to the full interval of the target bitmap.

The conversion works as follows:

The pixels equal to or around the minimum value of the bitmap will go to black (0).
The pixels equal to or around the maximum values of the bitmap will go white (255 for 8-bit, 0xFFF for 12-bit, 0xFFFF for 16-bit, 0xFFFFFFFF for 32-bit).
The other pixels will be scaled to go to an intermediary gray value.

Refer to Working with floating point bitmaps for more details on floating point bitmaps.

Grayscale 8-bit Function - Before

Grayscale 8-bit Function - After

View additional platform support for this Grayscale 8-bit function.

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 FEATURE2
example.
This example loads a bitmap and changes it to 8-bit grayscale.

L_INT GrayScaleBitmapExample(L_VOID) 
{ 
   L_INT nRet; 
   BITMAPHANDLE LeadBitmap;   /* Bitmap handle to hold the loaded image. */ 
 
   /* Load the bitmap, keeping the bits per pixel of the file */ 
   nRet = L_LoadBitmap (MAKE_IMAGE_PATH(TEXT("IMAGE1.CMP")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if(nRet != SUCCESS) 
      return nRet; 
 
   /* Change the bitmap to grayscale */ 
   nRet = L_GrayScaleBitmap(&LeadBitmap, 8 ); 
   if(nRet != SUCCESS) 
      return nRet; 
 
   nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("Result.BMP")), &LeadBitmap, FILE_BMP, 24, 0, NULL); 
   if(nRet != SUCCESS) 
      return nRet; 
 
   L_FreeBitmap(&LeadBitmap); 
   return SUCCESS; 
}