#include "l_bitmap.h"

L_LTIMGEFX_API L_INT L_SkeletonBitmap(pBitmap, nThreshold, uFlags)


pointer to the bitmap handle

L_INT nThreshold;

threshold value

L_UINT32 uFlags;


Finds the skeleton of objects or regions in a bitmap.




Pointer to the bitmap handle that references the bitmap for which to find the skeleton.


Threshold value used to binarize the bitmap before finding the skeleton. This parameter is ignored if the bitmap is a binary bitmap. The threshold range for 16, 48 and 64-bit images is from 0 to 65535 for unsigned images, and from  32768 to +32767 for signed images. For 12-bit images, the threshold range is from 0 to 4095 for unsigned images, and from  2048 to +2047 for signed images. Otherwise, it is from 0 to 255.


Reserved for future use. Must be 0.



The function was successful.

< 1

An error occurred. Refer to Return Codes.


This function finds the skeleton of regions or objects in a binary bitmap. The white color represents the objects and the black color represents the background. If the bitmap is not a 1-bit image, the threshold will be used to transform the bitmap into a binary image before finding the skeleton.

If the bitmap has a region, this function works only on the region.

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.

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

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


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


Win32, x64, Linux.

See Also


L_CombineBitmap, L_IntensityDetectBitmap, L_SharpenBitmap, L_SpatialFilterBitmap, L_EdgeDetectorBitmap, L_GlowFilterBitmap, L_CorrelationBitmap, L_DiffuseGlowBitmap, L_HighPassFilterBitmap, L_MaskConvolutionBitmap


Detecting and Enhancing Edges and Lines


Raster Image Functions: Image Processing: Filtering Images


Color Halftone and Halftone Images


Raster Image Functions: Detecting and Enhancing Edges and Lines


This example loads a bitmap and finds its edges using L_EdgeDetectorBitmap then produces the skeleton of these edges

L_INT SkeletonBitmapExample(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("sample5.cmp")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if(nRet !=SUCCESS) 
      return nRet; 
   /* Find the edges in the bitmap*/ 
   nRet = L_EdgeDetectorBitmap (&LeadBitmap,60, EDG_SOBEL_ALL, 0); 
   if(nRet !=SUCCESS) 
      return nRet; 
   nRet = L_SkeletonBitmap(&LeadBitmap, 128, 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  
   return SUCCESS; 

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