# 计算机图形学中的2D转换算法实现|S1（对象缩放）

2021年3月21日17:18:44 发表评论 345 次浏览

``````1. Make a 2x2 scaling matrix S as:
Sx 0
0  Sy
2. For each point of the polygon.
(i) Make a 2x1 matrix P, where P[0][0] equals
to x coordinate of the point and P[1][0]
equals to y coordinate of the point.
(ii) Multiply scaling matrix S with point
matrix P to get the new coordinate.
3. Draw the polygon using new coordinates.``````

``````// C program to demonstrate scaling of abjects
#include<stdio.h>
#include<graphics.h>

// Matrix Multiplication to find new Coordinates.
// s[][] is scaling matrix. p[][] is to store
// points that needs to be scaled.
// p[0][0] is x coordinate of point.
// p[1][0] is y coordinate of given point.
void findNewCoordinate( int s[][2], int p[][1])
{
int temp[2][1] = { 0 };

for ( int i = 0; i < 2; i++)
for ( int j = 0; j < 1; j++)
for ( int k = 0; k < 2; k++)
temp[i][j] += (s[i][k] * p[k][j]);

p[0][0] = temp[0][0];
p[1][0] = temp[1][0];
}

// Scaling the Polygon
void scale( int x[], int y[], int sx, int sy)
{
// Triangle before Scaling
line(x[0], y[0], x[1], y[1]);
line(x[1], y[1], x[2], y[2]);
line(x[2], y[2], x[0], y[0]);

// Initializing the Scaling Matrix.
int s[2][2] = { sx, 0, 0, sy };
int p[2][1];

// Scaling the triangle
for ( int i = 0; i < 3; i++)
{
p[0][0] = x[i];
p[1][0] = y[i];

findNewCoordinate(s, p);

x[i] = p[0][0];
y[i] = p[1][0];
}

// Triangle after Scaling
line(x[0], y[0], x[1], y[1]);
line(x[1], y[1], x[2], y[2]);
line(x[2], y[2], x[0], y[0]);
}

// Driven Program
int main()
{
int x[] = { 100, 200, 300 };
int y[] = { 200, 100, 200 };
int sx = 2, sy = 2;

int gd, gm;
detectgraph(&gd, &gm);
initgraph(&gd, &gm, " " );

scale(x, y, sx, sy);
getch();

return 0;
}``````