LECTURE 13

Graphics programming in C language

Programs:

text

mode

e6_1.c,

e6_2

graphics mode e7_1.c ... e7_5A.c

Tomasz Zieliński

MEMORY USAGE IN TEXT AND GRAPHICS MODES

RAM memory

Command.com

memory

for

programs

Stack

Interrupt survices

Text mode

In/Out devices

Graphics mode

A:0000

B:0000

0:0000

Address

64 kB

64 kB

10 times 64 kB

Graphics

card

Monitor

(hexadecimaly)

11 times 64 kB

SCREEN IN GRAPHICS MODE

640

(0, 0)

(479, 639)

MODE VGA

480

B

G

Other graphics

modes:

320 x 200 (CGA)
640 x 480 (VGA)
800 x 600 (SVGA)
1024 x 768 (XGA)
1280 x 800 (WXGA)
1280 x 1024 (SXGA)
1600 x 1200 (UXGA)

720 x 480 (NTSC)
720 x 576 (PAL)
1280 x 720 (HD 1)
1920 x 1080 (HD 2)

8 b

8 bits

8 b

R

E.g. 1000 pixels x 1000 pixels x

8

bits

x

8 bits

x

8

bits

= 24 000 000 bits

Digital image as a matrix of numbers

a)

b)

x(1, 1)

x(M, N)

x(M, 1)

x(2, 1)

x(3, 1)

x(1, 2)

x(2, 2)

x(3, 2)

x(M, 2)

x(1, N)

x(2, N)

x(3, N)

x(4, 1)

x(4, 2)

x(4, N)

N

M

n

m

11

236

117

43

98

177

22

43

165

125

234

155

33

76

249

0

0

133

44

87

149

0

0

199

55

99

135

217

168

111

66

121

77

88

99

110

6

6

c)

5

10

15

20

25

5

10

15

20

25

0

100

200

n

m

x(

m

,n

)

d)

5

25

20

15

10

5

10

15

20

25

Analog image

⇒ digital image

y

x

x

y

discretization in space

quantization of values

analog image

digital image

matrix of numbers

y

x

x

y

y

x

m

n

Line scanning of digital image

scanning line number 10

1

5

10

15

20

y

1

5

10

15

20

pixel value, grey level number

1

5

10

15

20

64

128

255

10

1

5

15

192

160

→

0

100

200

300

400

500

column number n

0

50

100

150

200

250

300

gr

ey

le

ve

l

hat

hair

VIDEO AS A 3-D MATRIX

film frame 1

film frame 2

film frame 3

n

m

time

!!! Data from Computed Tomography (CT) are 3-D matrices also !!!

CODING COLORS

Analog standard

NTSC

(

YIQ

)

− USA:

0,299

0,587

0,114

0,736(

) 0,268(

) 0,596

0, 274

0,321

0,478(

) 0.413(

) 0,211

0,523

0,311

Y

R

G

B

I

R Y

B Y

R

G

B

Q

R Y

B Y

R

G

B

=

+

+



 =

−

−

−

=

−

−



 =

−

+

−

=

−

+



Analog standard

PAL

(

YUV

)

− EUROPE:

0,299

0,587

0,114

0,492(

)

0,147

0,289

0,436

0,877(

) 0,615

0,515

0,100

Y

R

G

B

U

B Y

R

G

B

V

R Y

R

G

B

=

+

+



 =

−

= −

−

+



 =

−

=

−

−



Digital television,

DVD

(

YCbCr

):

0,299

0,587

0,114

0,564(

)

0,1687

0,3313

0,5

0,713(

)0,5

0,4187

0,0813

Y

R

G

B

Cb

B Y

R

G

B

Cr

R Y

R

G

B

=

+

+





=

−

= −

−

+





=

−

−

−



SCREEN IN TEXT MODE

background
color

MODE C80, BW80

(0, 0)

(24, 79)

80

25

I T L E

O P T I O

N

O P T I O

N

O P T I O

O P T I O

N

N

3

1
2

4

8 x 8

forground

kolor

[

]

T

SCREEN OF TEXT MODE

Table of ASCII codes

SCREEN OF TEXT MODE

Table of extended ASCII codes

(decimal number, character)

ZAPIS OBRAZU EKRANU

IN MEMORY

Text mode:

char

attributes

ASCII code of char

background

attributes

8 bits

4 bits

4 bits

attributes = color, possible blinking

Graphics mode:

color index in

palette

x bits

color index in

palette

x bits

color index in

palette

x bits

PALETTE OF COLORS IN GRAPHICS MODE

color =

c

R

⋅

R

⊕

c

G

⋅

G

⊕

c

B

⋅

B

Example:

palette

with 64 grey levels (8 bits per color)

Color index(number)

c

R

(RED)

c

G

(GREEN)

c

B

(BLUE)

0

0

0

0

1

4

4

4

2

8

8

8

3

12

12

12

4

16

16

16

5

20

20

20

...

...

...

...

61

244

244

244

62

248

248

248

63

252

252

252

C LANGUAGE FUNCTIONS FOR TEXT MODE

(Borland C/C++ ver. 3.11) ------------------------------------------------------------------------------------------------------------------------------------------------------

textmode( mode )

mode =

C80, C40, BW80, BW40 (Color, BlackWhite)

clrscr();

clear

screen

textcolor( color )

character color = BLACK, BLUE, GREEN, CYAN,

RED, MAGENTA, BROWN, ..., YELLOW, WHITE

textbackground( color )

background

color

textattr( color )

both: char color (upper 4bits), back color (lower 4b)

highvideo()

intensive color

lowvideo()

pale color

_setcursortype( type )

type = _NOCURSOR (without), _SOLIDCURSOR
(block), _NORMALCURSOR (underlining)

col = wherex()

return

x

coordinate of the

cursor

row = wherey()

return

y

coordinate of the

cursor

goto(

x,

y)

shift

cursor

to the point (x, y)

putch( ch )

print char in the actual

cursor

position

window( x1, y1, x2, y2)

active window (x1, y1) - (x2, y2), relative coordinates

cprintf(”%s”, text); cputs(”text”)

print text in the actual

cursor

position

ch = getch(); cscanf( ”%d”, &zmienna)

read char or number from keyboard

char bufor[82]; string = cgets(bufor)

read string of chars from keyboard buffer

/* Example 6.1 – GRAPHICS – Text mode - Borland C 3.11 DOS */

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

int

menu

( char *title, char *options[ ], int many, int x, int y, int dx );

void

frame

( int x, int y, int dx, int dy, char *title );

void

textline

( int x1, int y1, int x2, int y2, char c );

/* main program ------------------------------------------------------------------- */

void main()
{
char *title = "MENU";
char *options[] = { " 0000 ", " 1111 ", " 2222 ", " 3333 " };
int many = 4;
int column = 30, row = 10, width = 8;
int numer;

numer =

menu

( title, options, many, column, row, width);

printf("\n Option number %d has been chosen ! \n", numer );
}

/* Auxiliary functions ------------------------------------------------------------ */

int menu( char *title, char *options[ ], int many, int x, int y, int dx)
{
char c;
int i, num;
int xofs, yofs;

xofs = 1; yofs = 1;

// offset in frame

clrscr

();

// clear screen

_setcursortype

(_NOCURSOR);

// do not display cursor

frame

( x-1, y-1, dx+1, many+1, title );

// draw frame

window

( x, y, x+dx, y+many );

// define text window

// options[ 0 ] - intensive, blue letters on yellow background

highvideo

();

textcolor

( BLUE );

textbackground

( YELLOW );

gotoxy

( xofs, yofs );

cprintf

( "%s", options[ 0 ] );

// other options - pale, white letters on black screen

lowvideo

();

textcolor

( WHITE );

textbackground

( BLACK );

for( i=1; i<many; i++)
{

gotoxy

( xofs, yofs+i );

cprintf

( "%s", options[ i ] ); }

// CHOICE LOOP: the chosen option is changed via arrows
num = 0;
while( (c =getch()) != 13 )

// wait for ENTER

{
switch( c ) {

case 80:

// arrow down

lowvideo();

textcolor( WHITE ); textbackground( BLACK );

gotoxy

( xofs, yofs+num );

cprintf

("%s", options[ num ]);

num++;

if ( num > many-1 ) num = 0;

highvideo();

textcolor( BLUE ); textbackground( YELLOW );

gotoxy

( xofs, yofs+num );

cprintf

("%s", options[ num ]);

break;

case 72:

// arrow up

lowvideo();

textcolor( WHITE ); textbackground( BLACK );

gotoxy

( xofs, yofs+num );

cprintf

( "%s", options[ num ]);

num--;

if ( num < 0 ) num = many-1;

highvideo();

textcolor( BLUE );textbackground( YELLOW );

gotoxy

( xofs, yofs+num );

cprintf

("%s", options[ num ]);

break;

}

}
textattr( WHITE ) ; textcolor( WHITE );

// standard

window( 1, 1, 80, 25);

// whole screen

clrscr();

// clear screen

return( num );
}

/* ----------------------------------------------------------------------------------------- */

void

frame

( int x, int y, int dx, int dy, char *title)

{
char *text;

textcolor

( YELLOW );

// line color

// LINES

textline

( x, y, x+dx, y,

205 );

// horizontal upper

textline

( x, y+dy, x+dx, y+dy, 205 );

// horizontal lower

textline

( x, y, x, y+dy, 186 );

// vertical first

textline

( x+dx, y, x+dx, y+dy, 186 );

// vertical second

// CORNERS

gotoxy

( x, y );

putch

( 201 );

// upper left

gotoxy

( x+dx, y );

putch

( 187 );

// upper right

gotoxy

( x+dx, y+dy );

putch

( 188 );

// lower left

gotoxy

( x, y+dy );

putch

( 200 );

// lower right

strcpy( text, "[" );

// TITLE

strcat( text, title );
strcat( text, "]" );

gotoxy

( x+(dx-strlen(title))/2, y );

cprintf

( text );

textcolor( WHITE );
}
/* ---------------------------------------------------------------------------------------- */

void

textline

( int x1, int y1, int x2, int y2, char

c

)

{
int ix, iy;

if ( x1 == x2 )

// vertical line

{ for( iy=y1; iy<=y2; iy++ )

{

gotoxy

( x1, iy );

putch

(

c

); } }

if ( y1 == y2 )

// horizontal line

{ for( ix=x1; ix<=x2; ix++ )

{

gotoxy

( ix, y1 );

putch

(

c

); } }

}

C LANGUAGE FUNCTIONS FOR GRAPHICS MODE (1)

(Borland C/C++ ver. 3.11) ------------------------------------------------------------------------------------------------------------------------------------------------------

initgraph( &driver, &mode);

driver = DETECT, CGA, EGA, VGA

closegraph();

mode = VGALO, VGAMED, VGAHI (640 x 480)

MaxX = getmaxx();

return pixels resolution in ax x

MaxY = getmaxy();

return pixels resolution in ax y

cleardevice();

clear

screen

setviewport( x1, y1, x2, y2);

active window (x1, y1) - (x2, y2)

putpixel( x, y, color );

set color of the pixel (x, y)

color = getpixel( x, y);

get color from the pixel (x, y)

setcolor( color );

set active color for further drawings: pixels,lines

line( x1, y1, x2, y2);

line from point (x1, y1) to point (x2, y2)

moveto( x1, y1);

shift

cursor

to the point (x1, y1)

lineto( x2, y2 );

draw line from

cursor

to the point (x2, y2)

setlinestyle(

style

,

pattern

,

width

);

style

DOTTED_LINE

(dotted)

pattern

0xAB (bit pattern)

SOLID_LINE (solid)

width

CENTER_LINE

(dash-dot)

NORM_WIDTH

(normal)

DASHED_LINE

(dashed)

THICK_WIDTH

(thick)

USERBIT_LINE

(patrz

wzór)

C LANGUAGE FUNCTIONS FOR GRAPHICS MODE (2)

(Borland C/C++ ver. 3.11) ------------------------------------------------------------------------------------------------------------------------------------------------------

// WRITING TEXT IN GRAPHICS MODE

char *s;

//

horizon

: LEFT_TEXT, CENTER_TEXT,

sprintf( s, ”%d”, number );

//

RIGHT_TEXT

settextjustify(

horizon

,

vertical

);

//

vertical

: BOTTOM_TEXT, CENTER_TEXT,

outtext( x, y, s);

//

TOP_TEXT

Tekst

Tekst

Tekst

Tekst

Tekst

Tekst

Tekst

Tekst

Tekst

ANIMATION

(Borland C/C++ ver. 3.11) ------------------------------------------------------------------------------------------------------------------------------------------------------

void *bufor;

// store to buffer image from (x1,y1)

long size;

//

to

(x2,y2)

using

function

getimage()

size = imagesize( x1, y1, x2, y2);

// and next put this image in some other

bufor = malloc( size );

// place, performing logical operation

getimage( x1, y1, x2, y2, bufor );

// XOR, OR, AND on bits “existing” on

putimage( x, y, bufor, COPY_PUT );

// the screen and „overlaid”

XOR_PUT

//

getimage

// beginning

OR_PUT

//

LOOP: putimage(XOR); // old position

AND_PUT

//

putimage(XOR); // new position

NOT_PUT

//

goto LOOP

LOOP:

setactivepage(0);

//

in graphics memory we can have a few graphical

// draw on page(0);

//

„pages”, numbered 0, 1, 2, ...

setvisualpage(0);

//

one page is drown, the other is displayed

setactivepage(1);

//

set page 1 active for drawing

// draw on page(0);

//

draw on page 1

setvisualpage(1);

//

set page 1 to be visualized (displayed)

goto

LOOP;

//

/* Example 7.1: GRAPHICS – graphics mode – Borland C 3.1 DOS*/
/* 2D plot - sum of a few sinusoids */

/* Include libraries ------------------------------------------------------------------*/
#include <stdio.h>
#include <conio.h>
#include <graphics.h>

// add graphics library

#include <math.h>

/* Define GLOBAL constants and variables --------------------------------*/
#define MaxDATA 500

// maximum length of data vector

int

GraphDriver;

// graphics driver

int GraphMode;

// graphics mode

int

ErrorCode;

// error code

/* Define your own functions ----------------------------------------------------*/

// not any

/****************************** Main program *******************************/
main()
{

/* Define LOCAL constants and variables ----------------------------------*/

float data[ MaxDATA ]; // vector with data to be plotted
int MaxX, MaxY;

// max resolution horizontally and vertically

int i, j;

// work indexes

float pi=3.1415927;

// constant

int sX, sY, lenX, lenY;

// other work variables

int nX, nY;

// described below

float fX, dX, fY, dY, miniY, maxiY, diffY, v; //
char *s;

/* Initialize graphics mode ------------------------------------------------------- */

GraphDriver = DETECT;

/* request for autodetection */

initgraph

( &GraphDriver, &GraphMode, "" );

/* initialization */

ErrorCode =

graphresult

();

/* result of initialization */

if( ErrorCode != grOk )

/* any error? */

{
printf("Graphics System Error: %s\n",

grapherrormsg

( ErrorCode ) );

return( 1 );
}
MaxX =

getmaxx

();

// horizontal resolution (number of pixels)

MaxY =

getmaxy

();

// vertical resolution (number of pixels)

cleardevice

();

// clear graphical screen

setviewport

( 0, 0, MaxX, MaxY, 0);

// view port = whole screen

/* Generation of data to be visualized ---------------------------------------*/
for( i = 0 ; i < MaxDATA; i++ )
data[ i ] = 0.1 + 0.5 * sin(2.*pi*i/100.) + 0.25 * cos(2.*pi*i/25.);

/* Visualization -----------------------------------------------------------------------*/
sX = 20;

// upper right plot corner in pixels (S-tart X)

sY = 20;

//

(S-tart Y)

lenX = MaxDATA;

// plot dimension horizontally (X)

lenY = MaxY-100;

// plot dimension vertically (Y)

nX = 5;

// X axis – number of segments

fX = 0.;

// X axis – first value of the axis description

dX = 100.;

// X axis – values spacing (difference)

nY = 8;

// Y axis - number of segments

fY = -1.0;

// Y axis - first value of the axis description

dY = 0.25;

// Y axis - values spacing (difference)

miniY = fY;

// Y axis - minimum value of the label

maxiY = fY + nY*dY;

// Y axis – maximum value of the label

diffY = maxiY - miniY;

// Y axis - difference max-min

setcolor

(getmaxcolor()/2);

// set white color

line

( sX, sY, sX+lenX, sY );

// FRAME

line

( sX+lenX, sY, sX+lenX, sY+lenY );

//

line

( sX+lenX, sY+lenY, sX, sY+lenY );

// four lines

line

( sX, sY+lenY, sX, sY );

//

settextjustify

( LEFT_TEXT, CENTER_TEXT);

// Y AXIS

for( i = 0 ; i <= nY; i++)

// description

{

//

sprintf

( s, "%6.2f", fY + i * dY );

//

outtextxy

( sX+lenX, sY+(nY-i)*lenY/nY, s );

//

}

settextjustify

( CENTER_TEXT, TOP_TEXT);

// X AXIS

for( i = 0 ; i <= nX; i++)

// description

{

//

sprintf

( s, "%3.0f", fX + i * dX );

//

outtextxy

( sX+i*lenX/nX, sY+lenY+8, s);

//

}

//

setlinestyle

( DOTTED_LINE, 0x00, NORM_WIDTH);

// GRID

for( i = 1 ; i < nY; i++)

//

{

line

( sX, sY+i*lenY/nY, sX+lenX, sY+i*lenY/nY ); }

// horizon

for( i = 1 ; i < nX; i++)

//

{

line

( sX+i*lenX/nX, sY, sX+i*lenX/nX, sY+lenY ); }

// vertical

setlinestyle

( SOLID_LINE, 0x00, NORM_WIDTH);

// PLOT

setcolor

(getmaxcolor());

// intensive white

v = data[ 0 ];

//

if ( v < miniY ) v=miniY;

//

if ( v > maxiY ) v=maxiY;

//

j = (int) ( ( (v-miniY)/diffY ) * lenY );

//

moveto

(

sX,

sY+lenY-j

);

//

for( i = 1; i < MaxDATA; i++ )

//

{

//

v = data[ i ];

//

if ( v < miniY ) v=miniY;

//

if ( v > maxiY ) v=maxiY;

//

j = (int) ( ( (v-miniY)/diffY ) * lenY );

//

lineto

(

sX+i,

sY+lenY-j

);

//

}

//

/* Wait for pressing the key <Escape> ------------------------------------------ */

setcolor

(getmaxcolor()-1);

// yellow color

settextjustify

( CENTER_TEXT, TOP_TEXT);

// how to center

outtextxy

( sX+lenX/2, MaxY-10, "WYJSCIE = Esc");

// info out

while( getch() != 27 );

/* The end ------------------------------------------------------------------------------*/

cleardevice();

// clear graphical screen

closegraph();

// close graphical mode

textmode(C80);

// return to text mode

clrscr();

// clear text screen

printf( "\n" );
printf( " Bye ! That’s all for now !\n" );
printf( "\n" );

return(0);

}