#include "ltwrappr.h"

virtual L_INT LBitmap::EdgeDetector (uThreshold, uFilter, uFlags = 0)

L_UINT uThreshold;

threshold value

L_UINT uFilter;

filter to be used

L_UINT32 uFlags;


Applies the specified edge filter to the class object's bitmap.




Threshold value used to determine which pixels are edge pixels. If the difference determined for a pixel is greater than this value, the pixel is an edge pixel.


Flag that indicates which edge detection filter to apply. Possible values are:

  Value Meaning
  EDG_SOBEL_VERT [0x0101] Detect the vertical edges
  EDG_SOBEL_HORZ [0x0102] Detect the horizontal edges
  EDG_SOBEL_ALL [0x0103] Detect horizontal & vertical edges
  EDG_PREWITT_VERT [0x0201] Detect the vertical edges
  EDG_PREWITT_HORZ [0x0202] Detect the horizontal edges
  EDG_PREWITT_ALL [0x0203] Detect horizontal & vertical edges
  EDG_LAPLACE_1 [0x0301] Detect vertical & horizontal edges
  EDG_LAPLACE_2 [0x0302] Detect general edges
  EDG_LAPLACE_3 [0x0303] Detect general edges. (The filter used for this option is different than the filter used for the EDG_LAPLACE_2 filter.)
  EDG_LAPLACE_DIAG [0x0304] Detect the diagonal edges
  EDG_LAPLACE_HORZ [0x0305] Detect the horizontal edges
  EDG_LAPLACE_VERT [0x0306] Detect the vertical edges
  EDG_GRADIENT_N [0x0401] Detect north edges
  EDG_GRADIENT_NE [0x0402] Detect north east edges
  EDG_GRADIENT_E [0x0403] Detect east edges
  EDG_GRADIENT_SE [0x0404] Detect south east edges
  EDG_GRADIENT_S [0x0405] Detect south edges
  EDG_GRADIENT_SW [0x0406] Detect south west edges
  EDG_GRADIENT_W [0x0407] Detect west edges
  EDG_GRADIENT_NW [0x0408] Detect north west edges
uFlags Reserved for future use. Must be 0.



The function was successful.

< 1

An error occurred. Refer to Return Codes.


Filters such as Sobel filter, Prewitt filter, Laplacian filter, and Gradient filter are used to determine the pixels belonging to edges in the bitmap.

This function can process the whole image or a region of the image.

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 only in the Document/Medical toolkits.

The threshold range for the 16, 48, and 64-bit bitmaps is from 0 to 65535 and for 12-bit bitmaps from 0 to 4095. Otherwise, it is from 0 to 255. The threshold is applied on channels separately.

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.

See Also


LBitmap::DiffuseGlow, LBitmap::HighPassFilter, LBitmap::MaskConvolution, LBitmap::IntensityDetect, LBitmap::Sharpen, LBitmap::SpatialFilter, LBitmap::EdgeDetector2, Class Members


Detecting and Enhancing Edges and Lines


Raster Image Functions: Image Processing: Filtering Images


Raster Image Functions: Detecting and Enhancing Edges and Lines


L_INT LBitmap__EdgeDetectorExample(LBitmap & Bitmap, L_TCHAR * szFile) 
   L_INT nRet; 
   nRet =Bitmap.Load(szFile); 
   if(nRet !=SUCCESS) 
      return nRet; 
   nRet =Bitmap.EdgeDetector(60, EDG_SOBEL_ALL); 
   if(nRet !=SUCCESS) 
      return nRet; 
   return SUCCESS; 

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