Scaling in C Language

 
 

Point (X,Y) is to be scaled by amount S_x and S_y to location (X',Y')

X' = S_x * X
Y' = S_y * Y

or P' = S * P where

P' = [X`,Y`]   , P  = [X,Y]  

S  = |  Sx  0  |

     |  0   Sy |

 where  Sx ,Sy are scaling factor in x and y directions  

Scaling is performed about the origin (0,0) not about the center of the line/polygon/whatever
Case 1:Scale > 1 enlarges the object and moves it away from the origin.
Case 2:Scale = 1 leave the object alone
Case 3:Scale< 1 shrink the object and move it towards the origin.
Case 4: Uniform scaling: S_x = S_y




#include<stdio.h>
#include<graphics.h>
#include<conio.h>
#include<stdlib.h>
void main()
{
    int gdriver=DETECT,gmode;
    int midx=350,midy=300;
    int x1,y1,x2,y2;
    int x,y,i,sx,sy;
    clrscr();
    initgraph(&gdriver,&gmode,"c:/tc/bgi");
    printf("\n Enter the 1st co-ordinate=");
    scanf("%d%d",&x1,&y1);
    printf("\n Enter the 2nd co-ordinate=");
    scanf("%d%d",&x2,&y2);
    clrscr();
    line(midx,midy-150,midx,midy+150);
    line(midx+150,midy,midx-150,midy);
    outtextxy(midx,midy," origin");
    //printf("\n Before refelction");
    rectangle(midx+x1,midy+y1,midx+x2,midy+y2);
    getch();
    printf("\n Enter the scaling factor(sx,sy)=");
    scanf("%d%d",&sx,&sy);
    rectangle(midx+sx*x1,midy+sx*y1,midx+sx*x2,midy+sx*y2);
    getch();


}