main.cpp File Reference

#include <math.h>
#include <stdio.h>
#include <string>

Go to the source code of this file.

Macros
#define	_USE_MATH_DEFINES
	Generate a pair of optical illusions in SVG format.

Functions
bool	OpenSVG (FILE *&output, const std::string &fname, size_t w, size_t h)
	Open SVG file. More...
void	CloseSVG (FILE *&output)
	Close SVG file. More...
void	DrawCircleOfSquares (FILE *output, size_t cx, size_t cy, float r, size_t sw, bool parity)
	Draw a circle of squares to a file in SVG format. More...
void	OpticalIllusion1 (const std::string &fname, size_t w, size_t n, float r0, float dr, size_t sw, const char dark[], const char light[], const char bgclr[])
	Draw the first optical illusion to a file in SVG format. More...
void	SelectEllipseColor (FILE *output, size_t i, bool parity)
	Select ellipse color based on index. More...
void	DrawCircleOfEllipses (FILE *output, size_t cx, size_t cy, float r, float r0, float r1, size_t n, float theta, float dtheta, bool parity, size_t flip=999999)
	Draw circle of ellipses to a file in SVG format. More...
void	DrawTripleCircle (FILE *output, size_t cx, size_t cy, float r, float r0, float r1, size_t n, bool flip=false)
	Draw 3 concentric circles of ellipses to a file in SVG format. More...
void	OpticalIllusion2 (const std::string &fname, size_t w, size_t n, float r, float r0, float r1, const char dark[], const char light[], const char bgclr[])
	Draw the second optical illusion to a file in SVG format. More...
int	main ()
	Main. More...

Variables
const float	PI = 3.14159265358979323846f
	Pi.

Function Documentation

CloseSVG()

void CloseSVG

(

FILE *&

output

)

Close SVG file.

Print a close svg tag and close the SVG file.

Parameters

output

Reference to file pointer.

Definition at line 79 of file main.cpp.

DrawCircleOfEllipses()

void DrawCircleOfEllipses	(	FILE *	output,
		size_t	cx,
		size_t	cy,
		float	r,
		float	r0,
		float	r1,
		size_t	n,
		float	theta,
		float	dtheta,
		bool	parity,
		size_t	flip = 999999
	)

Draw circle of ellipses to a file in SVG format.

Draw a circle of elipses oriented so that the long axis of eah ellipse is perpendicular to a line drawn from the center of the circles to the center of the ellipse. This function outputs SVG transform and SVG ellipse tags to the output file. Used for optical illusion 2.

Parameters

output	Output file pointer.
cx	X coordinate of center of image in pixels.
cy	Y coordinate of center of image in pixels.
r	Radius of circle.
r0	Long radius of ellipses.
r1	Short radius of ellipses.
n	Number of ellipses in ring.
theta	Angle to first ellipse.
dtheta	Angle delta.
parity	True if first ellipse is black, false if white.
flip	True to clip the ordering of colots of ellipses.

Definition at line 232 of file main.cpp.

DrawCircleOfSquares()

void DrawCircleOfSquares	(	FILE *	output,
		size_t	cx,
		size_t	cy,
		float	r,
		size_t	sw,
		bool	parity
	)

Draw a circle of squares to a file in SVG format.

This function outputs SVG transform and SVG rect tags to the output file, alternating between black and white. The squares are spaced apart by approximately half a square width and tilted slightly from the perpendicular to a line drawn from the center of the circle to the center of the square. The number of squares is chosen so as to fit the spacing constraint, which need not be exact for the optical illusion to work. Used for optical illusion 1.

Parameters

output	File pointer.
cx	Image center x.
cy	Image center y.
r	Circle radius in pixels.
sw	Square width and height.
parity	Square initial orientation parity.

Definition at line 113 of file main.cpp.

DrawTripleCircle()

void DrawTripleCircle	(	FILE *	output,
		size_t	cx,
		size_t	cy,
		float	r,
		float	r0,
		float	r1,
		size_t	n,
		bool	flip = false
	)

Draw 3 concentric circles of ellipses to a file in SVG format.

This function calls DrawCircleOfEllipses() three times, once for each circle of ellipses. The middle circle is drawn first, then the inner circle, then the outer circle. The parameters for the calls DrawCircleOfEllipses() are chosen so as to achieve the following.

The inner circle starts with a black ellipse centered at the top and alternates with white ellipses each spaced roughly one ellipse long-axis apart for a total of 36 ellipses as shown in the next image.

The inner circle also has 36 ellipses, but it starts with a gap centered at the top with black ellipses to the left and right and a gap centered at the bottom with white ellipses to the left and right. Black and white alternate for the rest of the circle.

The outer circle of a ring is similar to the inner circle but has black and white interchanged.

Used for optical illusion 2.

Parameters

output	Pointer to output file.
cx	X coordinate of center of image in pixels.
cy	Y coordinate of center of image in pixels.
r	Radius of braid.
r0	Long radius of ellipses.
r1	Short radius of ellipses.
n	Number of ellipses in ring.
flip	True to flip the ordering of colors of ellipses.

Definition at line 293 of file main.cpp.

main()

int main

(

)

Main.

Create two optical illusions and save them as SVG files. The actual work is done by functions OpticalIllusion1() and OpticalIllusion2(), called with various parameters.

Returns

0.

Definition at line 367 of file main.cpp.

OpenSVG()

bool OpenSVG	(	FILE *&	output,
		const std::string &	fname,
		size_t	w,
		size_t	h
	)

Open SVG file.

Open an SVG file for writing and print the header tag and an open svg tag.

Parameters

output	[out] Reference to output file pointer.
fname	File name without extension.
w	Image width.
h	Image height.

Returns

true if open succeeded.

Definition at line 50 of file main.cpp.

OpticalIllusion1()

void OpticalIllusion1	(	const std::string &	fname,
		size_t	w,
		size_t	n,
		float	r0,
		float	dr,
		size_t	sw,
		const char	dark[],
		const char	light[],
		const char	bgclr[]
	)

Draw the first optical illusion to a file in SVG format.

The image consists of four concentric circles of tilted squares, alternating between light and dark squares. This function outputs an SVG style tag (the use of which refices the SVG file size) and the background rectangle tag, then calls DrawCircleOfSquares() once for each circle of squares required.

Parameters

fname	File name without extension.
w	Width and height of image in pixels.
n	Number of circles.
r0	Initial circle radius.
dr	Radius delta.
sw	Width of squares.
dark	A dark SVG color.
light	A light SVG color.
bgclr	A mid-range SVG color for the background.

Definition at line 159 of file main.cpp.

OpticalIllusion2()

void OpticalIllusion2	(	const std::string &	fname,
		size_t	w,
		size_t	n,
		float	r,
		float	r0,
		float	r1,
		const char	dark[],
		const char	light[],
		const char	bgclr[]
	)

Draw the second optical illusion to a file in SVG format.

The image consists of a pair of concentric rings, each of which is made up of three concentric circles of ellipses. This function outputs an SVG style tag (the use of which refices the SVG file size) and the background rectangle tag, then calls DrawTripleCircle() twice, once for each triplet of circles.

Parameters

fname	File name without extension.
w	Width and height of image in pixels.
n	Number of ellipses in ring.
r	Radius of braid.
r0	Long radius of ellipses.
r1	Short radius of ellipses.
dark	A dark SVG color.
light	A light SVG color.
bgclr	A mid-range SVG color for the background.

Definition at line 327 of file main.cpp.

SelectEllipseColor()

void SelectEllipseColor	(	FILE *	output,
		size_t	i,
		bool	parity
	)

Select ellipse color based on index.

If parity is true, ellipse is black when i%4=0, white when ji%4==2, and blank when i%4==1 and i%4==3. If parity is false, black and white are flipped. This function outputs the appropriate class name, class="b" for black and class="w" for white, to the output file. Used for optical illusion 2.

Parameters

output	Output file pointer.
i	Ellipse index about circle.
parity	True if first ellipse is black, false if white.

Definition at line 204 of file main.cpp.