Custom Strokes
/*
* Copyright (c) 2000 David Flanagan. All rights reserved.
* This code is from the book Java Examples in a Nutshell, 2nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book (recommended),
* visit http://www.davidflanagan.com/javaexamples2.
*/
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.Stroke;
import java.awt.font.GlyphVector;
import java.awt.geom.GeneralPath;
import java.awt.geom.PathIterator;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
/** A demonstration of writing custom Stroke classes */
public class CustomStrokes extends JPanel{
static final int WIDTH = 750, HEIGHT = 200; // Size of our example
public String getName() {
return "Custom Strokes";
}
public int getWidth() {
return WIDTH;
}
public int getHeight() {
return HEIGHT;
}
// These are the various stroke objects we'll demonstrate
Stroke[] strokes = new Stroke[] { new BasicStroke(4.0f), // The standard,
// predefined
// stroke
new NullStroke(), // A Stroke that does nothing
new DoubleStroke(8.0f, 2.0f), // A Stroke that strokes twice
new ControlPointsStroke(2.0f), // Shows the vertices & control
// points
new SloppyStroke(2.0f, 3.0f) // Perturbs the shape before stroking
};
/** Draw the example */
public void paint(Graphics g1) {
Graphics2D g = (Graphics2D)g1;
// Get a shape to work with. Here we'll use the letter B
Font f = new Font("Serif", Font.BOLD, 200);
GlyphVector gv = f.createGlyphVector(g.getFontRenderContext(), "B");
Shape shape = gv.getOutline();
// Set drawing attributes and starting position
g.setColor(Color.black);
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g.translate(10, 175);
// Draw the shape once with each stroke
for (int i = 0; i < strokes.length; i++) {
g.setStroke(strokes[i]); // set the stroke
g.draw(shape); // draw the shape
g.translate(140, 0); // move to the right
}
}
public static void main(String[] a) {
JFrame f = new JFrame();
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
f.setContentPane(new CustomStrokes());
f.setSize(750,200);
f.setVisible(true);
}
}
/**
* This Stroke implementation does nothing. Its createStrokedShape() method
* returns an unmodified shape. Thus, drawing a shape with this Stroke is the
* same as filling that shape!
*/
class NullStroke implements Stroke {
public Shape createStrokedShape(Shape s) {
return s;
}
}
/**
* This Stroke implementation applies a BasicStroke to a shape twice. If you
* draw with this Stroke, then instead of outlining the shape, you're outlining
* the outline of the shape.
*/
class DoubleStroke implements Stroke {
BasicStroke stroke1, stroke2; // the two strokes to use
public DoubleStroke(float width1, float width2) {
stroke1 = new BasicStroke(width1); // Constructor arguments specify
stroke2 = new BasicStroke(width2); // the line widths for the strokes
}
public Shape createStrokedShape(Shape s) {
// Use the first stroke to create an outline of the shape
Shape outline = stroke1.createStrokedShape(s);
// Use the second stroke to create an outline of that outline.
// It is this outline of the outline that will be filled in
return stroke2.createStrokedShape(outline);
}
}
/**
* This Stroke implementation strokes the shape using a thin line, and also
* displays the end points and Bezier curve control points of all the line and
* curve segments that make up the shape. The radius argument to the constructor
* specifies the size of the control point markers. Note the use of PathIterator
* to break the shape down into its segments, and of GeneralPath to build up the
* stroked shape.
*/
class ControlPointsStroke implements Stroke {
float radius; // how big the control point markers should be
public ControlPointsStroke(float radius) {
this.radius = radius;
}
public Shape createStrokedShape(Shape shape) {
// Start off by stroking the shape with a thin line. Store the
// resulting shape in a GeneralPath object so we can add to it.
GeneralPath strokedShape = new GeneralPath(new BasicStroke(1.0f)
.createStrokedShape(shape));
// Use a PathIterator object to iterate through each of the line and
// curve segments of the shape. For each one, mark the endpoint and
// control points (if any) by adding a rectangle to the GeneralPath
float[] coords = new float[6];
for (PathIterator i = shape.getPathIterator(null); !i.isDone(); i
.next()) {
int type = i.currentSegment(coords);
Shape s = null, s2 = null, s3 = null;
switch (type) {
case PathIterator.SEG_CUBICTO:
markPoint(strokedShape, coords[4], coords[5]); // falls through
case PathIterator.SEG_QUADTO:
markPoint(strokedShape, coords[2], coords[3]); // falls through
case PathIterator.SEG_MOVETO:
case PathIterator.SEG_LINETO:
markPoint(strokedShape, coords[0], coords[1]); // falls through
case PathIterator.SEG_CLOSE:
break;
}
}
return strokedShape;
}
/** Add a small square centered at (x,y) to the specified path */
void markPoint(GeneralPath path, float x, float y) {
path.moveTo(x - radius, y - radius); // Begin a new sub-path
path.lineTo(x + radius, y - radius); // Add a line segment to it
path.lineTo(x + radius, y + radius); // Add a second line segment
path.lineTo(x - radius, y + radius); // And a third
path.closePath(); // Go back to last moveTo position
}
}
/**
* This Stroke implementation randomly perturbs the line and curve segments that
* make up a Shape, and then strokes that perturbed shape. It uses PathIterator
* to loop through the Shape and GeneralPath to build up the modified shape.
* Finally, it uses a BasicStroke to stroke the modified shape. The result is a
* "sloppy" looking shape.
*/
class SloppyStroke implements Stroke {
BasicStroke stroke;
float sloppiness;
public SloppyStroke(float width, float sloppiness) {
this.stroke = new BasicStroke(width); // Used to stroke modified shape
this.sloppiness = sloppiness; // How sloppy should we be?
}
public Shape createStrokedShape(Shape shape) {
GeneralPath newshape = new GeneralPath(); // Start with an empty shape
// Iterate through the specified shape, perturb its coordinates, and
// use them to build up the new shape.
float[] coords = new float[6];
for (PathIterator i = shape.getPathIterator(null); !i.isDone(); i
.next()) {
int type = i.currentSegment(coords);
switch (type) {
case PathIterator.SEG_MOVETO:
perturb(coords, 2);
newshape.moveTo(coords[0], coords[1]);
break;
case PathIterator.SEG_LINETO:
perturb(coords, 2);
newshape.lineTo(coords[0], coords[1]);
break;
case PathIterator.SEG_QUADTO:
perturb(coords, 4);
newshape.quadTo(coords[0], coords[1], coords[2], coords[3]);
break;
case PathIterator.SEG_CUBICTO:
perturb(coords, 6);
newshape.curveTo(coords[0], coords[1], coords[2], coords[3],
coords[4], coords[5]);
break;
case PathIterator.SEG_CLOSE:
newshape.closePath();
break;
}
}
// Finally, stroke the perturbed shape and return the result
return stroke.createStrokedShape(newshape);
}
// Randomly modify the specified number of coordinates, by an amount
// specified by the sloppiness field.
void perturb(float[] coords, int numCoords) {
for (int i = 0; i < numCoords; i++)
coords[i] += (float) ((Math.random() * 2 - 1.0) * sloppiness);
}
}
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