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L_SpatialFilterBitmap

Summary

Imposes a spatial filter on a bitmap. You can supply your own filter or use one of the predefined filters.

Syntax

#include "l_bitmap.h"

L_LTIMGEFX_API L_INT L_SpatialFilterBitmap(pBitmap, pFilter, uFlags)

Parameters

pBITMAPHANDLE pBitmap

Pointer to the bitmap handle that references the bitmap to be affected.

pSPATIALFLT pFilter

Pointer to the spatial filter to use. For predefined filters, refer to List of Spatial Filters. To define your own filter, refer to SPATIALFLT.

Returns

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

Comments

A spatial filter recomputes the brightness of each pixel in a bitmap by using a weighted averaging technique that considers the surrounding pixels. Spatial filters are used for operations such as sharpening an image or detecting edges within the image.

The L_SpatialFilterBitmap function works best with 24-bit, 16-bit, or grayscale bitmaps. If a bitmap uses a color palette, this function matches the new brightness value of each pixel to the nearest color in the existing palette.

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

This function supports 12 and 16-bit grayscale and 48 and 64-bit color images. Support for 12 and 16-bit grayscale and 48 and 64-bit color images is available in the Document and Medical Imaging toolkits.

This function does not support 32-bit grayscale images. It returns the error code ERROR_GRAY32_UNSUPPORTED if a 32-bit grayscale image is passed to this function.

Required DLLs and Libraries

LTIMGEFX
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 CHILD.C module of the DEMO example.
This example loads a bitmap and applies a Prewitt edge detection filter.

L_INT SpatialFilterBitmapExample(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("NaturalFruits.jpg")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   /* Apply a Prewitt edge detection filter */ 
   nRet = L_SpatialFilterBitmap(&LeadBitmap, FLT_PREWITT_HORZ, 0); 
   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; 
 
   //free bitmap 
   if (LeadBitmap.Flags.Allocated) 
      L_FreeBitmap(&LeadBitmap); 
 
   return SUCCESS; 
}