The pictorial representation and manipulation of data by a compute. The creation, display, and storage of pictures, with a computer

Transcription

1 Nihar Ranjan Roy

2 The pictorial representation and manipulation of data by a compute The creation, display, and storage of pictures, with a computer Computer graphics is a sub-field of computer science which studies methods for digitally synthesizing and manipulating visual content. Although the term often refers to the study of three-dimensional computer graphics, it also encompasses two-dimensional graphics and image processing Nihar Ranjan Roy 2

3 80x25 Cursor appears n(by default) 640x480 Cursor Disappears (by default) Precise access to screen locations Nihar Ranjan Roy 3

4 How to change the mode? first call the initgraph() function. void initgraph ( int *graphdriver, int *graphmode,char *pathtodriver); initgraph loads the graphics driver and puts the system into graphics mode. You can tell initgraph to use a particular graphics driver and mode, or to autodetect the attached video adapter at run time and pick the corresponding driver. Nihar Ranjan Roy 4

5 Simple graphics program? #include<graphics.h> //contains graphics //functions void main() { int gd=detect,gm; //graphics driver & mode initgraph(&gd,&gm,"c:\\tc\\bgi"); //initialise circle(320,240,100); //draw circle(c x,c y,radius) getch(); } Nihar Ranjan Roy 5

6 Graphics Driver? *graphdriver is an integer that specifies the graphics driver to be used. You can give it a value using a constant of the graphics_drivers enumeration type, which is defined in graphics.h and listed below. graphics_drivers constant Numeric value graphics_driver s constant Numeric value DETECT CGA 1 MCGA 2 EGA 3 EGA (requests autodetect) EGAMONO 5 IBM HERCMONO 7 ATT400 8 VGA 9 PC Nihar Ranjan Roy 6

7 Graphics Mode *graphmode is an integer that specifies the initial graphics mode Driver graphics_mode Value x Rows Palette Pages CGA CGAC x 200 C0 1 CGAC x 200 C1 1 CGAC x 200 C2 1 CGAC x 200 C3 1 CGAHI x color 1 Nihar Ranjan Roy 7

8 CGA color palettes Palette listings C0, C1, C2, and C3 refer to the four predefined fourcolor palettes available on CGA (and compatible) systems. You can select the background color (entry #0) in each of these palettes, but the other colors are fixed. Palette Number Three Colors 0 LIGHTGREEN LIGHTRED YELLOW 1 LIGHTCYAN LIGHTMAGENTA WHITE 2 GREEN RED BROWN 3 CYAN MAGENTA LIGHTGRAY Nihar Ranjan Roy 8

9 Driver graphics_mode Value x Rows Palette Pages MCGA MCGAC x 200 C0 1 MCGAC x 200 C1 1 MCGAC x 200 C2 1 MCGAC x 200 C3 1 MCGAMED x color 1 MCGAHI x color 1 EGA EGALO x color 4 EGAHI x color 2 EGA64 EGA64LO x color 1 EGA64HI x color 1 EGA-MONO EGAMONOHI x color 1 w/64k EGAMONOHI x color 2 w/256k HERC HERCMONOHI x color 2 Nihar Ranjan Roy 9

10 Driver graphics_mode Value x Rows Palette Pages ATT400 ATT400C x 200 C0 1 ATT400C x 200 C1 1 ATT400C x 200 C2 1 ATT400C x 200 C3 1 ATT400MED x color 1 ATT400HI x color 1 VGA VGALO x color 2 VGAMED x color 2 VGAHI x color 1 PC3270 PC3270HI x color 1 IBM8514 IBM8514HI x color? IBM8514LO x color? Nihar Ranjan Roy 10

11 Return Value Of Initialization Process initgraph always sets the internal error code; on success, it sets the code to 0. If an error occurred, *graphdriver is set to -2, -3, -4, or -5, and graphresult returns the same value as listed below: Constant Name Number Meaning grnotdetected -2 Cannot detect a graphics card grfilenotfound -3 Cannot find driver file grinvaliddriver -4 Invalid driver grnoloadmem -5 Insufficient memory to load driver Nihar Ranjan Roy 11

12 Colors in VGA Here are 16 colors declared in graphics.h as listed bellow. BLACK 0 BLUE: 1 GREEN 2 CYAN: 3 RED 4 MAGENTA: 5 BROWN: 6 LIGHTGRAY 7 DARKGRAY: 8 LIGHTBLUE: 9 LIGHTGREEN: 10 LIGHTCYAN: 11 LIGHTRED: 12 LIGHTMAGENTA 13 YELLOW: 14 WHITE: 15 Nihar Ranjan Roy 12

13 initgraph(&gdriver, &gmode, ""); /* read result of initialization */ errorcode = graphresult(); if (errorcode!= grok) /* an error occurred */ { printf("graphics error: %s\n", grapherrormsg(errorcode)); printf("press any key to halt:"); getch(); exit(1); /* return with error code */ } Nihar Ranjan Roy 13

14 Fill Colors void far setcolor(int color); //setcolor sets the current drawing color to color, which can range from 0 to getmaxcolor. void far setbkcolor(int color); //setbkcolor sets the background to the color specified by color. void far setfillstyle(int pattern, int color); //setfillstyle sets the current fill pattern and fill color. Nihar Ranjan Roy 14

15 The parameter pattern in setfillstyle is as follows: Names Value Means Fill With... EMPTY_FILL 0 Background color SOLID_FILL 1 Solid fill LINE_FILL LTSLASH_FILL 3 /// SLASH_FILL 4 ///, thick lines BKSLASH_FILL 5 \\\, thick lines LTBKSLASH_FILL 6 \\\ HATCH_FILL 7 Light hatch XHATCH_FILL 8 Heavy crosshatch INTERLEAVE_FILL 9 Interleaving lines WIDE_DOT_FILL 10 Widely spaced dots CLOSE_DOT_FILL 11 Closely spaced dots USER_FILL 12 User-defined fill pattern Nihar Ranjan Roy 15

16 Few more Functions int poly[12]={350,450, 350,410, 430,400, 350, 350, 300,430, 350,450 }; circle(100,100,50); outtextxy(75,170, "Circle"); rectangle(200,50,350,150); outtextxy(240, 170, "Rectangle"); ellipse(500, 100,0,360, 100,50); outtextxy(480, 170, "Ellipse"); line(100,250,540,250); outtextxy(300,260,"line"); sector(150, 400, 30, 300, 100,50); outtextxy(120, 460, "Sector"); drawpoly(6, poly); outtextxy(340, 460, "Polygon"); Nihar Ranjan Roy 16

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18 Pixel void far putpixel(int x,int u,int color); //set the color of the pixel at location (x,y) with the specified color Unsigned far getpixel(int x, int y); //Retreive the color value fo the pixel at location (x,y) Nihar Ranjan Roy 18

19 LINES line(x1,y1,x2,y2); //draw a line from (x1,y1) and (x2,y2) lineto(x2,y2); //draw a line from current position to (X2,y2) linerel(x1,y1,x2,y2); //draw a line from current position to a relative distance of (X2,y2) Nihar Ranjan Roy 19

20 Current Position (CP) void far moveto(x1,y1) //Move the cursor to the new position (x1,y1) void far moverel(dx,dy) //Move the cursor to the new position whose relative distance from current position is (dx,dy) Nihar Ranjan Roy 20

21 Mouse Handling in C The various mouse functions can be accessed by setting up the AX register with different values (service number) and issuing interrupt number 51. The functions are listed bellow Interrupt Service Purpose Reset mouse and get status Call with AX = 0 Returns: AX = FFFFh If mouse support is available Ax = 0 If mouse support is not available Show mouse pointer Call with AX = 1 Returns: Nothing Hide mouse pointer Call with AX = 2 Returns: Nothing Nihar Ranjan Roy 21

22 Get mouse position and button status Call with AX = 3 Returns: BX = mouse button status Bit Significance 0 button not pressed 1 left button is pressed 2 right button is pressed 3 center button is pressed CX = x coordinate DX = y coordinate Set mouse pointer position Call with AX = 4 CX = x coordinate DX = y coordinate Returns: Nothing Set horizontal limits for pointer Call with AX = 7 CX = minimum x coordinate DX = maximum x coordinate Returns: Nothing Set vertical limits for pointer Call with AX = 8 CX = minimum y coordinate DX = maximum y coordinate Nihar Returns: Ranjan Roy Nothing 22

23 Problem Write a program in which the mouse cursor is visible and its limit is set to (x1,y1) to (x2,y2). Nihar Ranjan Roy 23

24 int callmouse() { in.x.ax=1; //show mouse int86(51,&in,&out); return 1; } #include<graphics.h> #include<stdio.h> #include<conio.h> #include<dos.h> union REGS in, out; void restrictmouseptr(int x1,int y1,int x2,int y2) { in.x.ax=7; //set horizontal limit for mouse in.x.cx=x1; //Min X in.x.dx=x2; //Max X int86(51,&in,&out); in.x.ax=8; //set Vertical limit for the mouse in.x.cx=y1; //min Y in.x.dx=y2; //max Y int86(51,&in,&out); } Nihar Ranjan Roy 24

25 void main() { } int x,y,cl,a,b; int g=detect,m; clrscr(); initgraph(&g,&m,"c:\\tc\\bgi"); rectangle(100,100,550,400); callmouse(); restrictmouseptr(100,100,550,400); getch(); Nihar Ranjan Roy 25

26 Few more functions for mouse handling int callmouse() int mousehide() { { in.x.ax=1; in.x.ax=2; int86(51,&in,&out); int86(51,&in,&out); return 1; return 1; } } void mouseposi(int &xpos,int &ypos,int &click) { } in.x.ax=3; int86(51,&in,&out); click=out.x.bx; xpos=out.x.cx; ypos=out.x.dx; void setposi(int &xpos,int &ypos) { in.x.ax=4; in.x.cx=xpos; in.x.dx=ypos; int86(51,&in,&out); } Nihar Ranjan Roy 26