Answer:
import java.lang.*; //for using Math.cos() and Math.sin() and Math.toRadians() funcitons in rotate method
public class PolygonTransform
{
public static double[] copy(double[] array)
{
double[] newArray = new double[array.length];
for(int i=0;i<array.length;i++)
{
newArray[i] = array[i];
return newArray;
}
}
public static void scale(double[]x,double[]y,double alpha)
{
for(int i=0;i<x.length;i++)
{
x[i] *= alpha;
y[i] *= alpha;
}
}
public static void translate(double[]x,double[]y,double dx,double dy)
{
for(int i=0;i<x.length;i++)
{
x[i] += dx;
y[i] += dy;
}
}
public static void rotate(double[] x, double[]y,double theta)
{
double rad = Math.toRadians(theta);
double temp;
for(int i=0;i<x.length;i++)
{
temp = x[i]; //For storing temporarily the previous value of x before changing so tha it can be used in changing y
x[i] = x[i]*Math.cos(rad) - y[i]*Math.sin(rad);
y[i] = y[i]*Math.cos(rad) + temp*Math.sin(rad);
}
}
public static void main(String args[])
{
//This is just implementing you testcase discripted.
double[]x = new double[4];
double[]y = new double[4];
StdDraw.setScale(-5.0, +5.0);
x = { 0, 1, 1, 0 };
y = { 0, 0, 2, 1 };
double alpha = 2.0;
StdDraw.setPenColor(StdDraw.RED);
StdDraw.polygon(x, y);
scale(x, y, alpha);
StdDraw.setPenColor(StdDraw.BLUE);
StdDraw.polygon(x, y);
// Translates polygon by (2, 1).
StdDraw.setScale(-5.0, +5.0);
x = { 0, 1, 1, 0 };
y = { 0, 0, 2, 1 };
double dx = 2.0, dy = 1.0;
StdDraw.setPenColor(StdDraw.RED);
StdDraw.polygon(x, y);
translate(x, y, dx, dy);
StdDraw.setPenColor(StdDraw.BLUE);
StdDraw.polygon(x, y);
// Rotates polygon 45 degrees.
StdDraw.setScale(-5.0, +5.0);
x = { 0, 1, 1, 0 };
y = { 0, 0, 2, 1 };
double theta = 45.0;
StdDraw.setPenColor(StdDraw.RED);
StdDraw.polygon(x, y);
rotate(x, y, theta);
StdDraw.setPenColor(StdDraw.BLUE);
StdDraw.polygon(x, y);
}
}
Explanation:
