Contour stencil set construction. More...

#include <stdio.h>
#include "sset.h"
#include "imageio.h"

Include dependency graph for sset.c:

Data Structures
struct	stencilentry
	A single contour stencil $\mathcal{S}$ . More...

struct	stencilsetcell
	A cell in a contour stencil, $\Omega_k \subset \mathbb{R}^2$ . More...

struct	stencilqvec
	Quantized vector. More...

struct	ssetstruct
	A contour stencil set $\Sigma$ . More...

Macros
#define	NUMANGLES 64
	The angular resolution for stencil quantization. More...

#define	QUAD_RES 8
	Number of quadrature panels to use for integrals. More...

#define	INITIAL_CAPACITY 16
	Initial capacity of a stencil set. More...

#define	STABILITY_THRESH 1e-4
	Stability threshold. More...

Typedefs
typedef struct ssetstruct	ssettype
	A contour stencil set $\Sigma$ . More...

Functions
void	FreeStencilSet (sset *Set)
	Free a stencil set. More...

sset *	NewStencilSet (double StencilRadius, double(Psf)(double, double, const void ), const void *PsfParam, double PsfRadius)
	Create a new stencil set. More...

int	GetNumStencils (const sset *Set)
	Get the number of stencils in a stencil set. More...

const void *	GetPsfParam (const sset *Set)
	Get the PSF parameter pointer. More...

double	GetPsfRadius (const sset *Set)
	Get the support radius of the PSF. More...

double	EvalPhi (const sset *Set, int S, double x, double y)
	Evaluate the $\varphi_\mathcal{S}$ associated with a stencil. More...

int	AddStencil (sset Set, double(Phi)(double, double, const void ), const void PhiParam, double Rotation, int(DrawFun)(pen Pen, const void Param), const void DrawParam, const float *DrawColor)
	Add a stencil to a stencil set. More...

int	StencilConfusion (double ConfusionMatrix, sset Set)
	Compute the confusion matrix of a stencil set. More...

int	PrintStencilConfusion (sset *Set)
	Print stencil confusion information about a stencil set. More...

void	FitStencils (int Stencil, const sset Set, const float *Image, int ImageWidth, int ImageHeight)
	Determine the best-fitting stencil at each point in an image. More...

int	DrawContours (const char FileName, int OutputWidth, int OutputHeight, double ScaleFactor, const int Stencil, const sset Set, const float Input, int InputWidth, int InputHeight)
	Visualize the estimated contours. More...

int	DrawContoursEps (const char EpsFile, const int Stencil, const sset Set, const float Input, int InputWidth, int InputHeight)
	Visualize the estimated contours as an EPS image. More...

int	DrawContoursSvg (const char SvgFile, const char BgFile, const int Stencil, const sset Set, const float *Input, int InputWidth, int InputHeight)
	Visualize the estimated contours as an SVG image. More...

Variables
double()(double, double, const void )	GetPsf (const sset *Set)
	Get the PSF. More...

Detailed Description

Contour stencil set construction.

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

This program is free software: you can use, modify and/or redistribute it under the terms of the simplified BSD License. You should have received a copy of this license along this program. If not, see http://www.opensource.org/licenses/bsd-license.html.

Definition in file sset.c.

Macro Definition Documentation

#define INITIAL_CAPACITY 16

Initial capacity of a stencil set.

Definition at line 25 of file sset.c.

#define NUMANGLES 64

The angular resolution for stencil quantization.

Definition at line 21 of file sset.c.

#define QUAD_RES 8

Number of quadrature panels to use for integrals.

Definition at line 23 of file sset.c.

#define STABILITY_THRESH 1e-4

Stability threshold.

Definition at line 28 of file sset.c.

Typedef Documentation

typedef struct ssetstruct ssettype

A contour stencil set $\Sigma$ .

A stencil set is a collection of contour stencils. This is represented as an array ssetstruct::Stencil of type stencilentry. For computational efficiency, an array of quantized stencil vectors stencilqvec is also stored in ssetstruct::StencilTable. The locations of the cells are stored in stencilsetcell::Cell. The point spread function (PSF) to model the sampling of the input image is specified by ssetstruct::Psf.

ssetstruct is the definition of sset, which is encapsulated by forward declaration in sset.h.

Stencil sets are managed with the following functions:

NewStencilSet(): create a new sset
FreeStencilSet(): free an sset
AddStencil(): add a stencil to an sset
GetNumStencils(): get the number of stencils in the set
GetPsf(): get the PSF function pointer
GetPsfParam(): get the PSF parameters PsfParam
GetPsfRadius(): get the PSF radius

Function Documentation

int AddStencil	(	sset *	Set,
		double()(double, double, const void )	Phi,
		const void *	PhiParam,
		double	Rotation,
		int()(pen Pen, const void *Param)	DrawFun,
		const void *	DrawParam,
		const float *	DrawColor
	)

Add a stencil to a stencil set.

Parameters

Set	the stencil set
Phi	the distance function from which to derive the stencil
PhiParam	parameters for the distance function
Rotation	rotation of the stencil
DrawFun	function that draws the stencil
DrawParam	parameter for DrawFun
DrawColor	RGB color for drawing the stencil

Returns: 1 on success, 0 on failure

Definition at line 522 of file sset.c.

int DrawContours	(	const char *	FileName,
		int	OutputWidth,
		int	OutputHeight,
		double	ScaleFactor,
		const int *	Stencil,
		const sset *	Set,
		const float *	Input,
		int	InputWidth,
		int	InputHeight
	)

Visualize the estimated contours.

Parameters

Output	output image
OutputWidth,OutputHeight	dimensions of the output image
ScaleFactor	scale factor between input and output images
Stencil	best-fitting stencils $\mathcal{S}^\star$
Set	the stencil set
Input	input image
InputWidth,InputHeight	dimensions of the input image

Renders a visualization of the estimated contours to the output image. A nearest neighbor interpolation of the input image is created where the colors are darkened and converted to grayscale. For each pixel, the best-fitting stencil is drawn by calling the stencil's stencilentry::DrawFun.

Definition at line 1049 of file sset.c.

int DrawContoursEps	(	const char *	EpsFile,
		const int *	Stencil,
		const sset *	Set,
		const float *	Input,
		int	InputWidth,
		int	InputHeight
	)

Visualize the estimated contours as an EPS image.

Parameters

EpsFile	output EPS file name
Stencil	best-fitting stencils $\mathcal{S}^\star$
Set	the stencil set
Input	input image
InputWidth,InputHeight	dimensions of the input image

Returns: 1 on success, 0 on failure

Renders a visualization of the estimated contours as an EPS image. For each pixel, the best-fitting stencil is drawn by calling the stencil's stencilentry::DrawFun.

Definition at line 1120 of file sset.c.

int DrawContoursSvg	(	const char *	SvgFile,
		const char *	BgFile,
		const int *	Stencil,
		const sset *	Set,
		const float *	Input,
		int	InputWidth,
		int	InputHeight
	)

Visualize the estimated contours as an SVG image.

Parameters

SvgFile	output SVG file name
BgFile	output background image file name (PNG or JPEG)
Stencil	best-fitting stencils $\mathcal{S}^\star$
Set	the stencil set
Input	input image
InputWidth,InputHeight	dimensions of the input image

Returns: 1 on success, 0 on failure

Renders a visualization of the estimated contours as an SVG image. For each pixel, the best-fitting stencil is drawn by calling the stencil's stencilentry::DrawFun.

Definition at line 1210 of file sset.c.

double EvalPhi	(	const sset *	Set,
		int	S,
		double	x,
		double	y
	)

Evaluate the $\varphi_\mathcal{S}$ associated with a stencil.

Parameters

Set	the stencil set
S	index of the stencil
x,y	location to evaluate

Evaluate the distance function $\varphi_\mathcal{S}$ associated with stencil S at (x,y). The stencil rotation from stencilentry::PhiTrans is applied.

Definition at line 502 of file sset.c.

void FitStencils	(	int *	Stencil,
		const sset *	Set,
		const float *	Image,
		int	ImageWidth,
		int	ImageHeight
	)

Determine the best-fitting stencil at each point in an image.

Parameters

Stencil	the selected best-fitting stencils $\mathcal{S}^\star$
Set	stencil set to use
Image	the input image
ImageWidth,ImageHeight	image dimensions

This is the main routine for determining the best-fitting stencils on an image. The result is stored in Stencil, which should be an array of size ImageWidth by ImageHeight. For each pixel, the index of the best-fitting stencil is stored in Stencil.

For computational efficiency, the stencil fitting uses the quantized stencil vectors ssetstruct::StencilTable to approximate the cell total variations

$V_{i,j}(\mathcal{S}, v) \approx |\mathcal{S}_{i,j}| \cdot V_{i,j}\bigl( (\!\begin{smallmatrix} \cos \theta \\ \sin \theta \end{smallmatrix}\!), v\bigr), \quad |\theta - \angle \mathcal{S}_{i,j}| \le \tfrac{\pi}{128}.$

First, the cell total variation are computed for each pixel at each angle 0, ..., NUMANGLES-1. Then then stencils are computed by summing the cell total variations. Finally, the stencil with the smallest total variation is identified as the best-fitting stencil,

$\mathcal{S}^\star(k) = \operatorname*{arg\,min}_{\mathcal{S}\in\Sigma} \, V\bigl(\mathcal{S},v(\cdot-k)\bigr).$

If the difference between the smallest and second smallest total variations is below a threshold, the circle stencil is selected.

Definition at line 819 of file sset.c.

void FreeStencilSet ( sset * Set )

Free a stencil set.

Parameters

Set	the stencil set to free

Frees all memory associated with a stencil set.

Definition at line 244 of file sset.c.

int GetNumStencils ( const sset * Set )

Get the number of stencils in a stencil set.

Parameters

Set	the stencil set

Returns: the number of stencils in Set

Definition at line 453 of file sset.c.

const void* GetPsfParam ( const sset * Set )

Get the PSF parameter pointer.

Parameters

Set	the stencil set

Returns: the PSF parameters

Definition at line 475 of file sset.c.

double GetPsfRadius ( const sset * Set )

Get the support radius of the PSF.

Parameters

Set	the stencil set

Returns: the PSF support radius

Definition at line 486 of file sset.c.

sset* NewStencilSet	(	double	StencilRadius,
		double()(double, double, const void )	Psf,
		const void *	PsfParam,
		double	PsfRadius
	)

Create a new stencil set.

Parameters

StencilRadius	the circular radius of $\Omega$
Psf	point spread function modeling the sampling of the input image
PsfParam	parameters to pass to Psf
PsfRadius	support radius of Psf

Returns: an sset* on success, NULL on failure

Definition at line 393 of file sset.c.

int PrintStencilConfusion ( sset * Set )

Print stencil confusion information about a stencil set.

Parameters

Set	the stencil set

Returns: 1 on success, 0 on failure

Prints information from the stencil confusion matrix computed by StencilConfusion().

Definition at line 715 of file sset.c.

int StencilConfusion	(	double *	ConfusionMatrix,
		sset *	Set
	)

Compute the confusion matrix of a stencil set.

Parameters

ConfusionMatrix	pointer to an array to hold the result
Set	the stencil set

Returns: 1 on success, 0 on failure

For each distance function $\varphi$ used in the stencil set, all stencil TVs are computed. The results are stored in column-major order in ConfusionMatrix as

$\text{\tt ConfusionMatrix[i + j*GetNumStencils(Set)]} = V(\mathcal{S}_j, h * \varphi_i).$

The stencil associated with a distance function should have the lowest TV value, that is, the diagonal entries should be the smallest in each column. Small off-diagonal entries indicate stencils that are likely to be confused.

Definition at line 615 of file sset.c.

Variable Documentation

double(*)(double, double, const void*) GetPsf(const sset *Set)

Get the PSF.

Parameters

Set	the stencil set

Returns: function pointer to the PSF

Definition at line 464 of file sset.c.

Data Structures

Macros

Typedefs

Functions

Variables

Detailed Description

Macro Definition Documentation

Typedef Documentation

Function Documentation

Variable Documentation