edgen - Edge library routines.

NAME

libEdgenHD.a, sobel, gauss, SepOpt, Opt1D, Opt2D, derich, diff, work_out_grad, non_max, spaceck, ppfit, HysteresisThresh, Do_link, WriteEdgeStrAndDesc.,

DESCRIPTION

this manual gives the various routines that can be used by linking libEdgenHD.a to your program and including the header files. Two points need to be pointed out. Firstly, in most cases, the outputs need to be allocated for prior to processing. Secondly, functions parameters are generally arranged as inputs to function, output from functions and required parameters.

SYNOPSIS 

"edgen.h"  
"petrou.h" need to be included when compiling your programs. 

void sobel(FARY* image, FARY* dx, FARY* dy) 
void gauss(FARY* image, FARY* dx, FARY* dy, int mask_len, float tau) 
void SepOpt(FARY* image, FARY* dx, FARY* dy, int mask_len,float s) 
void Opt1D(FARY* image,FARY* dx, FARY* dy, int mask_len, float s) 
void Opt2D(FARY* image, FARY* dx, FARY* dy, FARY* smooImage, 
					     int mask_len, float s) 
void derich(FARY* image,FARY* dx,FARY* dy, float alpha, float omega) 
void diff(FARY* image, FARY* dx, FARY* dy) 

work_out_grad(FARY* dx, FARY* dy, FARY* grad) 

void non_max(FARY* dx, FARY* dy,  FARY *grad, 
	     FARY* max_SuppGrad, 
	     float *mean2, int four_con) 
void spaceck(FARY* dx,FARY* dy,FARY* grad, 
	     FARY* maxSuppGrad, 
	     FARY* xOfset,FARY* yOfset) 

void ppfit(FARY *dx, FARY *dy, FARY *grey,t_LL allStrs, 
	   FARY* dxOfSet, FARY* dyOffset) 

void HysteresisThresh (FARY *grad, BARY* edgeImage, double up_thr, double low_thr) 
t_LL Do_link(BARY *edgeImage) 
void WriteEdgeStrAndDesc(char *gfout,t_LL allStrings, FARY *dx, FARY *dy, 
			 FARY *max_supp_grad, FARY *xOfset, FARY *yOfset, 
			 int dirOut, int magOut, int strNumOut, int impDirSw) 


 
<h3>  Convolution  routines: </h3>
Having read the image into a FARY type structure (see ary manual for 
further details), the following convolutions can be performed to obtain 
dx and dy which are themselves FARYs (note that memory needs to be 
allocated for dx, dy prior to calling the routine): 

 

void sobel(FARY* image, FARY* dx, FARY* dy); 

 
void gauss(FARY* image, FARY* dx, FARY* dy, int mask_len, float tau) 

 
void SepOpt(FARY* image, FARY* dx, FARY* dy, int mask_len,float s) 

 
void Opt1D(FARY* image,FARY* dx, FARY* dy, int mask_len, float s) 

 
void Opt2D(FARY* image, FARY* dx, FARY* dy, FARY* smooImage,  
					     int mask_len, float s) 
void derich(FARY* image,FARY* dx,FARY* dy, float alpha, float omega) 

 
void diff(FARY* image, FARY* dx, FARY* dy); 



  Gradient  Calculation: 

Given dx and dy, the following routine works out the gradient image. 
The gradient image is a FARY which needs to have allocated memory for. 

work_out_grad(FARY* dx, FARY* dy, FARY* grad) 



  Non-Maximum  Routines: 

Two non-maximum routines are available both requiring dx,dy and grad information. 
The output is put in a FARY structure which should have memory  
allocated for. 

void non_max(FARY* dx, FARY* dy,  FARY *grad, 
             FARY* max_SuppGrad, 
	     float *mean2, int four_con) 


or for subpixel accuracy (note xOfset and yOfset are FARYs which need to 
be allocated for). They contain the exact location of the edge coordinate. 

void spaceck(FARY* dx,FARY* dy,FARY* grad, 
	     FARY* maxSuppGrad, 
	     FARY* xOfset,FARY* yOfset) 



void ppfit(FARY *dx, FARY *dy, FARY *grey,t_LL allStrs, 
	   FARY* dxOffset, FARY* dyOffset) 



  Hysteresis  Thresholding: 

This routine takes in the non-maximum suppressed image and performs  
Cannys hysteresis thresholding. The output is in a BARY (Byte Ary) structure  
and has zeros except at edge locations where it has values of 1. 

void HysteresisThresh (FARY *grad, BARY* edgeImage, double up_thr, double low_thr) 



  Linking  

This routine outputs connected components. Its retuens a list of 
connected strings. Each string is a list of points of type (t_i2D) which 
is a structure containning x, y and th.  

t_LL Do_link(BARY* edgeImage) 



  writing  to .gf file 

This routine takes in edge strings and writes the data to an o/p .gf file. 
It also (for speed) performs the direction operation. 

void WriteEdgeStrAndDesc(char *gfout,t_LL allStrings, FARY *dx, FARY *dy, 
			 FARY *max_supp_grad, FARY *xOfset, FARY *yOfset, 
		         int dirOut, int magOut, int strNumOut, int impDirSw) 

 
Any switch which is not used can be set to 0. 



  AUTHOR  

Homam Dabis, University of Surrey, h.dabis@ee.surrey.ac.uk. 


18-Oct-94. Automatically converted by man2html,
 written by G.Matas (g.matas@ee.surrey.ac.uk)