How to create star shape in Java?

Question

I am trying to make some shapes with Java. I created two rectangles with two different colors, but I want to create a star shape, and I cannot find a useful source to help me with this.

Here is my code:

import java.awt.*; import javax.swing.*; public class shapes extends JPanel{ @Override public void paintComponent(Graphics GPHCS){ super.paintComponent(GPHCS); GPHCS.setColor(Color.BLUE); GPHCS.fillRect(25,25,100,30); GPHCS.setColor(Color.GRAY); GPHCS.fillRect(25,65,100,30); GPHCS.setColor(new Color(190,81,215)); GPHCS.drawString("This is my text", 25, 120); } } 

Answer 1

You can try using a polygon and some basic math:

  int midX = 500; int midY = 340; int radius[] = {118,40,90,40}; int nPoints = 16; int[] X = new int[nPoints]; int[] Y = new int[nPoints]; for (double current=0.0; current<nPoints; current++) { int i = (int) current; double x = Math.cos(current*((2*Math.PI)/max))*radius[i % 4]; double y = Math.sin(current*((2*Math.PI)/max))*radius[i % 4]; X[i] = (int) x+midX; Y[i] = (int) y+midY; } g.setColor(Color.WHITE); g.fillPolygon(X, Y, nPoints); 

Answer 2

You can also use existing classes, for example. http://java-sl.com/shapes.html for regular polygons and stars.

Answer 3

The Polygon class can be thought of as an inherited class that was there since Java 1.0, but it can hardly be used in the new code. An odd way of specifying x / y coordinates in separate arrays and, more importantly, the fact that it only supports int[] arrays, limits its scope. Although it implements the Shape interface, there are more modern implementations of this interface that can be used to represent polygons. In most cases, describing a polygon as Path2D simpler and more flexible. You can create Path2D p = new Path2D.Double(); and then execute a sequence of calls to moveTo and lineTo to generate the desired shape.

The following program shows how the Path2D class can be used to create star-shaped shapes. The most important method is the createStar method. This is a very general one. He gets

• center coordinates for a star
• inner and outer radius of a star
• the number of rays that a star should have
• the angle at which the first ray should be (i.e., the angle of rotation of the star)

If desired, a simpler method can be wrapped around this - as with the createDefaultStar example in the code below.

The program shows different stars, painted in the form of lines and filled with different colors and radial gradient colors, as examples:

Full program like MCVE :

 import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Point; import java.awt.RadialGradientPaint; import java.awt.RenderingHints; import java.awt.Shape; import java.awt.geom.Path2D; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.SwingUtilities; public class DrawStarShape { public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { createAndShowGUI(); } }); } private static void createAndShowGUI() { JFrame f = new JFrame(); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.getContentPane().add(new DrawStarShapePanel()); f.setSize(600, 600); f.setLocationRelativeTo(null); f.setVisible(true); } } class DrawStarShapePanel extends JPanel { @Override protected void paintComponent(Graphics gr) { super.paintComponent(gr); Graphics2D g = (Graphics2D) gr; g.setColor(Color.WHITE); g.fillRect(0, 0, getWidth(), getHeight()); g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); g.setColor(Color.BLACK); g.draw(createDefaultStar(50, 200, 200)); g.setPaint(Color.RED); g.fill(createStar(400, 400, 40, 60, 10, 0)); g.setPaint(new RadialGradientPaint( new Point(400, 200), 60, new float[] { 0, 1 }, new Color[] { Color.RED, Color.YELLOW })); g.fill(createStar(400, 200, 20, 60, 8, 0)); g.setPaint(new RadialGradientPaint( new Point(200, 400), 50, new float[] { 0, 0.3f, 1 }, new Color[] { Color.RED, Color.YELLOW, Color.ORANGE })); g.fill(createStar(200, 400, 40, 50, 20, 0)); } private static Shape createDefaultStar(double radius, double centerX, double centerY) { return createStar(centerX, centerY, radius, radius * 2.63, 5, Math.toRadians(-18)); } private static Shape createStar(double centerX, double centerY, double innerRadius, double outerRadius, int numRays, double startAngleRad) { Path2D path = new Path2D.Double(); double deltaAngleRad = Math.PI / numRays; for (int i = 0; i < numRays * 2; i++) { double angleRad = startAngleRad + i * deltaAngleRad; double ca = Math.cos(angleRad); double sa = Math.sin(angleRad); double relX = ca; double relY = sa; if ((i & 1) == 0) { relX *= outerRadius; relY *= outerRadius; } else { relX *= innerRadius; relY *= innerRadius; } if (i == 0) { path.moveTo(centerX + relX, centerY + relY); } else { path.lineTo(centerX + relX, centerY + relY); } } path.closePath(); return path; } } 

Answer 4

I have 2 methods.

1)

 public static Bitmap drawStar(int W, int H, int color, boolean andRing) { Path path = new Path(); Bitmap output = Bitmap.createBitmap(W, H, Config.ARGB_8888); Canvas canvas = new Canvas(output); final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG); paint.setColor(color); float midW ,min ,fat ,half ,radius; if(andRing) { midW = W / 2; min = Math.min(W, H); half = min / 2; midW = midW - half; fat = min / 17; radius = half - fat; paint.setStrokeWidth(fat); paint.setStyle(Paint.Style.STROKE); canvas.drawCircle(midW + half, half, radius, paint); path.reset(); paint.setStyle(Paint.Style.FILL); path.moveTo( half * 0.5f, half * 0.84f); path.lineTo( half * 1.5f, half * 0.84f); path.lineTo( half * 0.68f, half * 1.45f); path.lineTo( half * 1.0f, half * 0.5f); path.lineTo( half * 1.32f, half * 1.45f); path.lineTo( half * 0.5f, half * 0.84f); } else { min = Math.min(W, H); half = min/2; path.reset(); paint.setStyle(Paint.Style.FILL); path.moveTo( half * 0.1f , half * 0.65f); path.lineTo( half * 1.9f , half * 0.65f); path.lineTo( half * 0.40f , half * 1.65f); path.lineTo( half , 0 ); path.lineTo( half * 1.60f, half * 1.65f); path.lineTo( half * 0.1f, half * 0.65f); } canvas.drawPath(path, paint); return output; } 

2)

  public static Bitmap drawStar(int W,int H,int spikes,int innerRadius,int outerRadius, int backColor,boolean border, int borderColor) { if(W < 10) W = 10; if(H < 10) H = 10; if(spikes < 5) spikes = 5; int smallL = W; if(H < W) smallL = H; if(outerRadius > smallL/2) outerRadius = smallL/2; if(innerRadius < 5) innerRadius = 5; if(border) { outerRadius -=2; innerRadius -=2; } Path path = new Path(); Bitmap output = Bitmap.createBitmap(W, H, Config.ARGB_8888); Canvas canvas = new Canvas(output); final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG); paint.setColor(backColor); int cx = W/2; int cy = H/2; double rot = Math.PI / 2 * 3; float x,y; double step = Math.PI / spikes; path.moveTo(cx, cy - outerRadius); for (int i = 0; i < spikes; i++) { x = (float) (cx + Math.cos(rot) * outerRadius); y = (float) (cy + Math.sin(rot) * outerRadius); path.lineTo(x, y); rot += step; x = (float) (cx + Math.cos(rot) * innerRadius); y = (float) (cy + Math.sin(rot) * innerRadius); path.lineTo(x, y); rot += step; } path.lineTo(cx, cy - outerRadius); path.close(); canvas.drawPath(path, paint); if(border) { paint.setStyle(Style.STROKE); paint.setStrokeWidth(2); paint.setColor(borderColor); canvas.drawPath(path, paint); } return output; }