#include "BIVISION.H"
HANDLE CALLBACK FilterEdgeSC( HANDLE hSrcDIB,
float fSF,
int iLow,
int iHigh,
float fRatio,
int iThinFactor,
int iWndSize,
BOOL bDoHysteresis
BOOL bShowDialog)
Description
This function will find edges on the input image by the Shen-Castan edge detection method. This function works for 8 and 24 bit per pixel images. Shen-Castan edge detector uses an optima filter function called Infinite Symmetric Exponential Filter (ISEF). This produces better signal to noise ratios and better localisation than Canny. First step is convolving the input image with the ISEF, then localization edges by zero crossing of the Laplacian (similar to the Marr-Hildreth algorithm). The approximation of Laplacian is computed by subtracting the original image from the smoothed one. The result is a band-limited Laplacian image. Next, a binary Laplacian image is generated by setting all the positive valued pixels to 1 and all others to 0. The candidate pixels are on the boundaries of the regions in th binary image. After improving the quality of edge pixels by false zero-crossing suppression, adaptive gradient thresholding and a hysteresis thresholding is applied finally.
Examples
The original 500 x 400 pixel image and the Shen-Castan edge detected image with fSF = 0.8, iLow = 20, iHigh = 22, fRatio = 0.99, iThinFactor = 0, iWndSize = 7 and bDoHysteresis = TRUE parameter values.
Parameters
|
HANDLE |
hSrcDIB |
Source DIB |
|
float |
fSF |
Smoothing factor used by the IESF filtering. See the description and examples above for further information and a possible value. |
|
int |
iLow |
Low threshold value of hysteresis thresholding. See the description and examples above for further information and a possible value. |
|
int |
iHigh |
High threshold value of hysteresis thresholding. See the description and examples above for further information and a possible value. |
|
float |
fRatio |
This parameter specifies the percents of pixels above the hysteresis thresholding. See the description and examples above for further information and a possible value. |
|
int |
iThinFactor |
Thinning factor (number of pixels). See the description and examples above for further information and a possible value. |
|
int |
iWndSize |
Size of window used by gradient thresholding. See the description and examples above for further information and a possible value. |
|
BOOL |
bDoHysteresis |
Do hysteresis thresholding with iLow and iHigh threshold values. |
|
BOOL |
bShowDialog |
This parameter specifies the displaying of the preview dialog. IMPORTANT: The preview dialog will only display, if there is BiDlgs.dll installed. |
Return values
Handle of the newly created DIB on success or NULL on failure.
Programming notes
Requirements
Header : Declared in BiVision.h; include BiVision.h.
Library : Use BiVision.lib.
DLLs : BiVision.dll.