Chan-Vese active contours without edges image segmentation. More...

#include "num.h"

Typedefs
typedef struct chanvesestruct	chanveseopt

Functions
chanveseopt *	ChanVeseNewOpt ()
	Create a new chanveseopt options object. More...

void	ChanVeseFreeOpt (chanveseopt *Opt)
	Free chanveseopt options object.

void	ChanVeseSetMu (chanveseopt *Opt, num Mu)
	Specify mu, the edge length penalty.

void	ChanVeseSetNu (chanveseopt *Opt, num Nu)
	Specify nu, the area penalty (may be positive or negative)

void	ChanVeseSetLambda1 (chanveseopt *Opt, num Lambda1)
	Specify lambda1, the fit weight inside the curve.

void	ChanVeseSetLambda2 (chanveseopt *Opt, num Lambda2)
	Specify lambda2, the fit weight outside the curve.

void	ChanVeseSetTol (chanveseopt *Opt, num Tol)
	Specify the convergence tolerance.

void	ChanVeseSetDt (chanveseopt *Opt, num dt)
	Specify the timestep.

void	ChanVeseSetMaxIter (chanveseopt *Opt, int MaxIter)
	Specify the maximum number of iterations.

void	ChanVeseSetPlotFun (chanveseopt Opt, int(PlotFun)(int, int, num, const num , const num , const num , int, int, int, void ), void *PlotParam)
	Specify plotting function. More...

void	ChanVesePrintOpt (const chanveseopt *Opt)

int	ChanVese (num Phi, const num f, int Width, int Height, int NumChannels, const chanveseopt *Opt)
	Chan-Vese two-phase image segmentation. More...

void	ChanVeseInitPhi (num *Phi, int Width, int Height)
	Default initialization for Phi.

void	RegionAverages (num c1, num c2, const num Phi, const num f, int Width, int Height, int NumChannels)
	Compute averages inside and outside of the segmentation contour.

Detailed Description

Chan-Vese active contours without edges image segmentation.

Author: Pascal Getreuer getre.nosp@m.uer@.nosp@m.gmail.nosp@m..com

Definition in file chanvese.h.

Function Documentation

int ChanVese	(	num *	Phi,
		const num *	f,
		int	Width,
		int	Height,
		int	NumChannels,
		const chanveseopt *	Opt
	)

Chan-Vese two-phase image segmentation.

Parameters

Phi	pointer to array to hold the resulting segmentation
f	the input image
Width,Height,NumChannels	the size of f
Tol	convergence tolerance
MaxIter	maximum number of iterations
Mu	length penalty
Nu	area penalty (positive penalizes area inside the curve)
Lambda1	fit penalty inside the curve
Lambda2	fit penalty outside the curve
dt	timestep
PlotFun	function for outputting intermediate results

This function performs Chan-Vese active contours two-phase image segmentation by minimizing the functional

$\begin{aligned}\operatorname*{arg\,min}_{c_1,c_2,C}\;& \mu \operatorname{Length}(C) + \nu\operatorname{Area}(\mathit{inside}(C)) \\ &+ \lambda_1 \int_{\mathit{inside}(C)}|f(x)-c_1|^2 \, dx + \lambda_2 \int_{\mathit{outside}(C)} |f(x) - c_2|^2 \, dx, \end{aligned}$

where the minimization is over all set boundaries C and scalars c1 and c2. The boundary C is implicitly represented by level set function Phi.

The input f can be a grayscale image or an image with any number of channels, i.e., three channels for a color image, or possibly many more in a hyperspectral image. If f is a multichannel image, the segmentation is done using the Chan, Sandberg, Vese vector extension of the Chan-Vese model,

$\begin{aligned}\operatorname*{arg\,min}_{c_1,c_2,C}\;& \mu \operatorname{Length}(C)+\nu\operatorname{Area}(\mathit{inside}(C)) \\ &+ \lambda_1 \int_{\mathit{inside}(C)}\|f(x)-c_1\|^2 \,dx+\lambda_2\int_{ \mathit{outside}(C)}\|f(x)-c_2\|^2\,dx,\end{aligned}$

where $\|\cdot\|$ denotes the Euclidean norm.

The data for f should be stored as a contiguous block of data of Width*Height*NumChannels elements, where the elements are ordered so that f[x + Width*(y + Height*k)] = kth component of the pixel at (x,y)

The array Phi is a contiguous array of size Width by Height with the same order as f. Phi is a level set function of the segmentation, meaning the segmentation is indicated by its sign: Phi[x + Width*y] >= 0 means (x,y) is inside the segmentation curve, Phi[x + Width*y] < 0 means (x,y) is outside. Before calling this routine, Phi should be initialized either by calling InitPhi or by setting it to a level set function of an initial guess of the segmentation. After this routine, the final segmentation is obtained from the sign of Phi.

The routine runs at most MaxIter number of iterations and stops when the change between successive iterations is less than Tol. Set Tol=0 to force the routine to run exactly MaxIter iterations.

Definition at line 127 of file chanvese.c.

chanveseopt* ChanVeseNewOpt ( )

Create a new chanveseopt options object.

This routine creates a new chanveseopt options object and initializes it to default values. It is the caller's responsibility to call ChanVeseFreeOpt to free the chanveseopt object when done.

Definition at line 369 of file chanvese.c.

void ChanVeseSetPlotFun	(	chanveseopt *	Opt,
		int()(int, int, num, const num , const num , const num , int, int, int, void *)	PlotFun,
		void *	PlotParam
	)

Specify plotting function.

Parameters

Opt	chanveseopt options object
PlotFun	plotting function
PlotParam	void pointer for passing addition parameters

Specifying the plotting function gives control over how ChanVese displays information. Setting PlotFun = NULL disables all normal display (error messages are still displayed).

An example PlotFun is

int ExamplePlotFun(int State, int Iter, num Delta,
    const num *c1, const num *c2,   const num *Phi,
    int Width, int Height, int NumChannels, void *Param)
{
    switch(State)
    {
    case 0:
        fprintf(stderr, " RUNNING   Iter=%4d, Delta=%7.4f\r", Iter, Delta);
        break;
    case 1:
        fprintf(stderr, " CONVERGED Iter=%4d, Delta=%7.4f\n", Iter, Delta);
        break;
    case 2:
        fprintf(stderr, " Maximum number of iterations exceeded!\n");
        break;
    }
    
    return 1;
}

The State argument is either 0, 1, or 2, and indicates ChanVese's status. Iter is the number of Bregman iterations completed, Delta is the change in the solution Delta = ||u^cur - u^prev||_2 / ||f||_2. Argument u gives a pointer to the current solution, which can be used to plot an animated display of the solution progress. PlotParam is a void pointer that can be used to pass additional information to PlotFun if needed.

Definition at line 483 of file chanvese.c.

Typedefs

Functions

Detailed Description

Function Documentation