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This chapter is from the book

This chapter is from the book

10.3 Paint Styles

When you fill a Shape, the Graphics2D object uses the settings associated with the internal Paint attribute. The Paint setting can be a Color (solid color), a GradientPaint (gradient fill gradually combining two colors), a TexturePaint (tiled image), or a new version of Paint that you write yourself. Use set_Paint and getPaint to change and retrieve the Paint settings. Note that setPaint and getPaint supersede the setColor and getColor methods that were used in Graphics.

Paint Classes

Arguments to the Graphics2D setPaint method (and return values of get_Paint) must implement the Paint interface. Here are the major built-in Paint classes.

Color

The Color class defines the same Color constants (Color.red, Color.yellow, etc.) as the AWT version but provides additional constructors to account for a transparency (alpha) value. A Color is represented by a 4-byte int value, where the three lowest bytes represent the red, green, and blue component, and the highest-order byte represents the alpha component. By default, colors are opaque with an alpha value of 255. A completely transparent color has an alpha value of 0. The common Color constructors are described below.

public Color(int red, int green, int blue)
public Color(float int, float green, float blue)

These two constructors create an opaque Color with the specified red, green, and blue components. The int values should range from 0 to 255, inclusive. The float values should range from 0.0f to 1.0f. Internally, each float value is converted to an int being multiplied by 255 and rounded up.

public Color(int red, int green, int blue, int alpha)
public Color(float red, float green, float blue, float alpha)

These two constructors create a Color object where the transparency value is specified by the alpha argument. See the preceding constructor for legal ranges for the red, green, blue, and alpha values.

Before drawing, you can also set the transparency (opaqueness) of a Shape by first creating an AlphaComposite object, then applying the AlphaComposite object to the Graphics2D context through the setComposite method. See S_ection 10.4 (Transparent Drawing) for details.

GradientPaint

A GradientPaint represents a smooth transition from one color to a second color. Two points establish a gradient line in the drawing, with one color located at one end point of the line and the second color located at other end point of the line. The color will smoothly transition along the gradient line, with parallel color bands extending orthogonally to the gradient line. Depending on the value of a boolean flag, the color pattern will repeat along the extended gradient line until the end of the shape is reached.

public GradientPaint(float xStart, float yStart,
       Color colorStart, float xEnd, float 
       yEnd, 
        Color colorEnd)

This constructor creates a GradientPaint, beginning with a color of colorStart at (xStart, yStart) and finishing with a color of col_orEnd at (xEnd, yEnd). The gradient is nonrepeating (a single gradient cycle).

public GradientPaint(float xStart, float yStart, 
    Color colorStart, float xEnd, float yEnd,
    Color colorEend, boolean repeat)

This constructor is the same as the preceding constructor, except that a boolean flag, repeat, can be set to produce a pattern that continues to repeat beyond the end point (cyclic).

TexturePaint

A TexturePaint is simply an image that is tiled across the shape. When creating a textured paint, you need to specify both the image on the tile and the tile size.

public TexturePaint(BufferedImage image, 
                  Rectangle2D tilesize)

The TexturePaint constructor maps a BufferedImage to a Rectangle2D and then tiles the rectangle. Creating a BufferedImage from a GIF or JPEG file is a pain. First, load an Image normally, get the size of the image, create a BufferedImage that sizes with BufferedImage.TYPE_INT_ARGB as the image type, get the BufferedImage's Graphics object through createGraphics, then draw the Image into the BufferedImage using drawImage.

Listing 10.4 is an example of applying a gradient fill prior to drawing a circle. The gradient begins with a red color (Color.red) located at (0, 0) and gradually changes to a yellow color (Color.yellow) located at (185, 185) near the center of the circle. The gradient fill pattern repeats across the remaining area of the circle, as shown in Figure 10–2.

Listing 10.4 GradientPaintExample.java

import java.awt.*;

/** An example of applying a gradient fill to a circle. The
 * color definition starts with red at (0,0), gradually
 * changing to yellow at (175,175).
 */

public class GradientPaintExample extends ShapeExample {
 private GradientPaint gradient =
  new GradientPaint(0, 0, Color.red, 175, 175, Color.yellow,
           true); // true means to repeat pattern

 public void paintComponent(Graphics g) {
  clear(g);
  Graphics2D g2d = (Graphics2D)g;
  drawGradientCircle(g2d);
 }

 protected void drawGradientCircle(Graphics2D g2d) {
  g2d.setPaint(gradient);
  g2d.fill(getCircle());
  g2d.setPaint(Color.black);
  g2d.draw(getCircle());
 }

 public static void main(String[] args) {
  WindowUtilities.openInJFrame(new GradientPaintExample(),
                 380, 400);
 }
}

Figure 10–2 A circle drawn with a gradient fill in Java 2D.

Tiled Images as Fill Patterns

To use tiled images, you first create a TexturePaint object and pass the object to the setPaint method of Graphics2D, just as with solid colors and gradient fills. The TexturePaint constructor takes a BufferedImage and a Rectangle2D as arguments. The BufferedImage specifies what to draw, and the Rectangle2D specifies where the tiling starts. The rectangle also determines the size of the image that is drawn; the BufferedImage is scaled to the rectangle size before rendering. Creating a BufferedImage to hold a custom drawing is relatively straightforward: call the BufferedImage constructor with a width, a height, and a type of BufferedImage.TYPE_INT_RGB, then call createGraphics on the buffered image to get a Graphics2D with which to draw. For example,

int width =32;
int height=32;
BufferedImage bufferedImage = 
 new BufferedImage(width, height
          BufferedImage.TYPE_INT_RGB); 
Graphics2D g2d = bufferedImage.createGraphics(); 
g2d.draw(someShape);
...
TexturePaint texture = 
 new TexturePaint(bufferedImage, 
          new Rectangle(0, 0, width, height));

The Graphics2D object returned from createGraphics is bound to the BufferedImage. At that point, any drawing to the Graphics2D object is drawn to the BufferedImage. The texture "tile" in this example is a rectangle 32 pixels wide and 32 pixels high, where the drawing on the tile is what is contained in the buffered image.

Creating a BufferedImage from an image file is a bit harder. First, load an Image from an image file, then use MediaTracker to be sure that the image is loaded, then create an empty BufferedImage by using the Image width and height. Next, get the Graphics2D with createGraphics, then draw the Image onto the BufferedImage. This process has been wrapped up in the get_BufferedImage method of the ImageUtilities class given in Listing 10.6.

An example of creating tiled images as fill patterns is shown in Listing 10.5. The result is presented in Figure 10–3. Two textures are created, one texture is an image of a blue drop, and the second texture is an image of Marty Hall contemplating another Java innovation while lounging in front of his vehicle. The first texture is applied before the large inverted triangle is drawn, and the second texture is applied before the centered rectangle is drawn. In the second case, the Rectangle is the same size as the BufferedImage, so the texture is tiled only once.

Listing 10.5 TiledImages.java

import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
import java.awt.image.*;

/** An example of using TexturePaint to fill objects with tiled
 * images. Uses the getBufferedImage method of ImageUtilities 
 * to load an Image from a file and turn that into a 
 * BufferedImage.
 */

public class TiledImages extends JPanel {
 private String dir = System.getProperty("user.dir");
 private String imageFile1 = dir + "/images/marty.jpg";
 private TexturePaint imagePaint1;
 private Rectangle imageRect;
 private String imageFile2 = dir + "/images/bluedrop.gif";
 private TexturePaint imagePaint2;
 private int[] xPoints = { 30, 700, 400 };
 private int[] yPoints = { 30, 30, 600 };
 private Polygon imageTriangle = new Polygon(xPoints, yPoints, 3);
 public TiledImages() {
  BufferedImage image =
   ImageUtilities.getBufferedImage(imageFile1, this);
  imageRect = new Rectangle(235, 70, image.getWidth(),
               image.getHeight());
  imagePaint1 = new TexturePaint(image, imageRect);
  image = ImageUtilities.getBufferedImage(imageFile2, this);
  imagePaint2 =
   new TexturePaint(image, new Rectangle(0, 0, 32, 32));
 }

 public void paintComponent(Graphics g) {
  super.paintComponent(g);
  Graphics2D g2d = (Graphics2D)g;
  g2d.setPaint(imagePaint2);
  g2d.fill(imageTriangle);
  g2d.setPaint(Color.blue);
  g2d.setStroke(new BasicStroke(5));
  g2d.draw(imageTriangle);
  g2d.setPaint(imagePaint1);
  g2d.fill(imageRect);
  g2d.setPaint(Color.black);
  g2d.draw(imageRect);
 }

 public static void main(String[] args) {
  WindowUtilities.openInJFrame(new TiledImages(), 750, 650);
 }
}

Listing 10.6 ImageUtilities.java

import java.awt.*;
import java.awt.image.*;

/** A class that simplifies a few common image operations, in
 * particular, creating a BufferedImage from an image file and
 * using MediaTracker to wait until an image or several images
 * are done loading.
 */

public class ImageUtilities {
 
 /** Create Image from a file, then turn that into a
  * BufferedImage.
  */

 public static BufferedImage getBufferedImage(String imageFile,
                        Component c) {
  Image image = c.getToolkit().getImage(imageFile);
  waitForImage(image, c);

  BufferedImage bufferedImage =
   new BufferedImage(image.getWidth(c), image.getHeight(c),
            BufferedImage.TYPE_INT_RGB);
  Graphics2D g2d = bufferedImage.createGraphics();
  g2d.drawImage(image, 0, 0, c);
  return(bufferedImage);
 }

 /** Take an Image associated with a file, and wait until it is
  * done loading (just a simple application of MediaTracker).
  * If you are loading multiple images, don't use this
  * consecutive times; instead, use the version that takes
  * an array of images.
  */

 public static boolean waitForImage(Image image, Component c) {
  MediaTracker tracker = new MediaTracker(c);
  tracker.addImage(image, 0);
  try {
   tracker.waitForAll();
  } catch(InterruptedException ie) {}
  return(!tracker.isErrorAny());
 }
 /** Take some Images associated with files, and wait until they
  * are done loading (just a simple application of
  * MediaTracker).
  */

 public static boolean waitForImages(Image[] images, Component c)  {
  MediaTracker tracker = new MediaTracker(c);
  for(int i=0; i<images.length; i++)
   tracker.addImage(images[i], 0);
  try {
   tracker.waitForAll();
  } catch(InterruptedException ie) {}
  return(!tracker.isErrorAny());
 }
}

Figure 10–3 By creation of TexturePaint definition, images can be tiled across any shape.

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