我在弄清楚三件事时遇到问题。 (使用绘图面板创建:http://www.buildingjavaprograms.com/DrawingPanel.java)
问题#1:绘制多边形,使其居中且不弯曲。画的点数多了就不太明显了。
问题#2:将星星的所有点连接在一起,形成一个巨大的圆圈(虚线)。我不明白为什么会发生这种情况,除非该方法不是最好的。
问题#3:当用少量的点绘制时,我注意到它没有正确绘制点,并且它看起来像一个正方形。
我非常感谢您的帮助!
import java.awt.*;
public class StarSampler {
public static void main(String[] args)
{
DrawingPanel panel = new DrawingPanel(500, 500);
Graphics2D g = panel.getGraphics();
g.setColor(Color.BLUE);
fillStar(g, 250, 250, 150, 5, 1);
}
public static void fillStar(Graphics2D g, int ctrX, int ctrY, int radius, int nPoints, double spikiness)
{
double xDouble[] = new double[2*nPoints];
double yDouble[] = new double[2*nPoints];
int xPoint[] = new int[100];
int yPoint[] = new int[100];
for (int i = 0; i < 2*nPoints; i++)
{
double iRadius = (i % 2 == 0) ? radius : (radius * spikiness);
double angle = (i * 720.0) / (2*nPoints);
xDouble[i] = ctrX + iRadius * Math.cos(Math.toRadians(angle));
yDouble[i] = ctrY + iRadius * Math.sin(Math.toRadians(angle));
for (int j = 0; j < nPoints; j++) // Casts for ints and doubles
{
xPoint[j] = (int) xDouble[j];
yPoint[j] = (int) yDouble[j];
}
}
g.fillPolygon(xPoint, yPoint, nPoints); // Creates polygon
// Polygon gets drawn crookedly
g.drawPolyline(xPoint, yPoint, nPoints); // Draws lines to connect points
// Two lines go straight to (0,0) when nPonts*2 and nothing without *2?
}
}
我的输出:
我的目标输出(没有标记点,两颗星只是举例):
您的代码存在逻辑问题或由于草率的编码风格造成的:
for (int j = 0; j < nPoints; j++) // Casts for ints and doubles
{
xPoint[j] = (int) xDouble[j];
yPoint[j] = (int) yDouble[j];
}
这段代码应该将多边形的所有部分转换为整数。这段代码有几个问题:
2 * nPoints
点,但只有一半被转换。这就是缺失的尖峰的来源圆是360度,不是720度。这段代码:
double angle = (i * 720.0) / (2*nPoints);
将改变创建点之间的角度。这意味着你要么只生成一半的尖峰(如果数量是偶数),要么生成很多交叉线(看起来也不错,但我猜不是你想要的)。
单位圆(与三角学部分相关)的定义方式使得 (1, 0) 是与中心成 0° 角的点。这也是创建第一个尖峰的地方。只需减去 90° 的角度即可将圆逆时针旋转 90°。
这是基于您的代码的工作解决方案。主要方法仅包含管理简单测试 UI 的代码:
import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
public class StarSampler
{
private static final int WIDTH = 500,
HEIGHT = 500,
RADIUS = 200;
private static final double SPIKINESS = 0.5;
public static void main(String[] args)
{
BufferedImage bi = new BufferedImage(500, 500, BufferedImage.TYPE_4BYTE_ABGR);
updateImage(5, bi);
JFrame frame = new JFrame("Some Test");
frame.setLayout(new BorderLayout());
frame.add(new JLabel(new ImageIcon(bi)), BorderLayout.CENTER);
//menu to update number of spikes
JPanel sub = new JPanel();
sub.setLayout(new BoxLayout(sub, BoxLayout.X_AXIS));
sub.add(new JLabel("Spikes: "));
JSpinner spikeSpinner = new JSpinner(new SpinnerNumberModel(5, 1, 500, 1));
spikeSpinner.addChangeListener(e -> {
updateImage((Integer) spikeSpinner.getModel().getValue(), bi);
SwingUtilities.invokeLater(()->frame.repaint());
});
sub.add(spikeSpinner);
frame.add(sub, BorderLayout.SOUTH);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
private static void updateImage(int nSpikes, BufferedImage bi)
{
int ctrX = WIDTH / 2, ctrY = HEIGHT / 2;
int nPoints = nSpikes * 2 + 1;
int xPoint[] = new int[nPoints];
int yPoint[] = new int[nPoints];
//generate star
for (int i = 0; i < nPoints; i++)
{
double iRadius = (i % 2 == 0) ? RADIUS : (RADIUS * SPIKINESS);
double angle = (i * 360.0) / (2*nSpikes);
xPoint[i] = (int) (ctrX + iRadius * Math.cos(Math.toRadians(angle - 90)));
yPoint[i] = (int) (ctrY + iRadius * Math.sin(Math.toRadians(angle - 90)));
}
//paint the star
Graphics2D g2 = (Graphics2D) bi.getGraphics();
g2.setColor(Color.blue);
g2.fillRect(0, 0, WIDTH, HEIGHT);
g2.setStroke(new BasicStroke(4.f));
g2.setColor(Color.yellow);
g2.drawPolyline(xPoint, yPoint, nPoints);
//insert control lines
g2.setStroke(new BasicStroke(1.f));
g2.setColor(Color.black);
for(int i = 0; i < nSpikes * 2; i++)
g2.drawLine(ctrX, ctrY, xPoint[i], yPoint[i]);
int w1 = RADIUS,
w2 = (int) (RADIUS * SPIKINESS);
g2.drawOval(ctrX - w1, ctrY - w1, w1 * 2, w1 * 2);
g2.drawOval(ctrX - w2, ctrY - w2, w2 * 2, w2 * 2);
}
}
这是JavaFX的解决方案,我使用并修改了上面的代码。
import javafx.scene.Group;
import javafx.scene.paint.Color;
import javafx.scene.shape.Polygon;
public class poly_star extends Group {
public poly_star(int RADIUS, int nSpikes, double SPIKINESS, Color col){
int ind=0;
int nPoints = nSpikes*2+1;
// Define an array to store the points of the polygon
double[] points = new double[nPoints * 2];
// Loop through each point and calculate its position
for (int i = 0; i < nPoints ; i++) {
double iRadius = (i % 2 == 0) ? RADIUS : (RADIUS * SPIKINESS);
// Calculate the angle for each point
double angle = (i * 360.0) / (2*nSpikes);
// X point position
points[ind] = iRadius * Math.cos(Math.toRadians(angle - 90));
// Y point position
points[ind+1] = iRadius* Math.sin(Math.toRadians(angle - 90));
System.out.println(" i:"+i + " // ind:" + ind);
ind +=2;
}
// Create a polygon object and set its points
Polygon STARpoly = new Polygon(points);
STARpoly.setFill(col);
getChildren().add(STARpoly);
}
}
您可以从任何地方调用它,只需添加您喜欢的参数即可:
poly_star myStar = new poly_star(280,13,0.6,Color.YELLOW);
myStar.setLayoutX( someXpos );
myStar.setLayoutY( someYpos );
getChildren().add(myStar);