问题
I've got a very basic rectangle drawing panel, but I would like to know if there is a simple way to add some sort of glow to the rectangles.
public class Blocks extends JPanel {
public void paintComponent(Graphics g) {
super.paintComponent(g);
this.setBackground(Color.BLACK);
for (int i = 1; i <= totalSteps; i++) {
g.setColor(Color.WHITE);
g.fillRect(100 + i*60, 260, 50, 50);
}
}
}
回答1:
Generating a "glow" effect is a little bit involved, depending on what you want to achieve.
I use this approach to generate glow effects for transparent/non-rectangular shapes (great for generating drop shadows for example).
This example basically creates a BufferedImage which represents the "glow", it then generates a "mask" which cuts the original BufferedImage out of it. I do it this way, as it allows me to draw the "glow" beneath transparent/translucent images. In your case, you could skip the "masking" process, but that's up to you.
You will also need a copy of the JHLabs, Image Filters, as I can't be bothered making my own blur filter
import com.jhlabs.image.GaussianFilter;
import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsEnvironment;
import java.awt.Transparency;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class GlowEffect {
public static void main(String[] args) {
new GlowEffect();
}
public GlowEffect() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public TestPane() {
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
int width = 50;
int height = 50;
int x = (getWidth() - width) / 2;
int y = (getHeight() - height) / 2;
BufferedImage img = generateGlow(width, height, 20, Color.YELLOW, 1f);
g2d.drawImage(img, x - ((img.getWidth() - width) / 2), y - ((img.getHeight() - height) / 2), this);
g2d.setColor(Color.WHITE);
g2d.fillRect(x, y, width, height);
g2d.dispose();
}
}
public static BufferedImage generateGlow(int width, int height, int size, Color glow, float alpha) {
BufferedImage source = createCompatibleImage(width, height);
Graphics2D g2d = source.createGraphics();
g2d.setColor(Color.WHITE);
g2d.fillRect(0, 0, width, height);
g2d.dispose();
return generateGlow(source, size, glow, alpha);
}
public static BufferedImage generateGlow(BufferedImage imgSource, int size, Color color, float alpha) {
int imgWidth = (int)Math.round(imgSource.getWidth() + (size * 2.5));
int imgHeight = (int)Math.round(imgSource.getHeight() + (size * 2.5));
BufferedImage imgMask = createCompatibleImage(imgWidth, imgHeight);
Graphics2D g2 = imgMask.createGraphics();
int x = Math.round((imgWidth - imgSource.getWidth()) / 2f);
int y = Math.round((imgHeight - imgSource.getHeight()) / 2f);
g2.drawImage(imgSource, x, y, null);
g2.dispose();
BufferedImage imgGlow = generateBlur(imgMask, size, color, alpha);
imgGlow = applyMask(imgGlow, imgMask, AlphaComposite.DST_OUT);
return imgGlow;
}
public static BufferedImage generateBlur(BufferedImage imgSource, int size, Color color, float alpha) {
GaussianFilter filter = new GaussianFilter(size);
int imgWidth = imgSource.getWidth();
int imgHeight = imgSource.getHeight();
BufferedImage imgBlur = createCompatibleImage(imgWidth, imgHeight);
Graphics2D g2 = imgBlur.createGraphics();
g2.drawImage(imgSource, 0, 0, null);
g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_IN, alpha));
g2.setColor(color);
g2.fillRect(0, 0, imgSource.getWidth(), imgSource.getHeight());
g2.dispose();
imgBlur = filter.filter(imgBlur, null);
return imgBlur;
}
public static BufferedImage createCompatibleImage(int width, int height) {
return createCompatibleImage(width, height, Transparency.TRANSLUCENT);
}
public static BufferedImage createCompatibleImage(int width, int height, int transparency) {
BufferedImage image = getGraphicsConfiguration().createCompatibleImage(width, height, transparency);
image.coerceData(true);
return image;
}
public static GraphicsConfiguration getGraphicsConfiguration() {
return GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
}
public static BufferedImage applyMask(BufferedImage sourceImage, BufferedImage maskImage, int method) {
BufferedImage maskedImage = null;
if (sourceImage != null) {
int width = maskImage.getWidth(null);
int height = maskImage.getHeight(null);
maskedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
Graphics2D mg = maskedImage.createGraphics();
int x = (width - sourceImage.getWidth(null)) / 2;
int y = (height - sourceImage.getHeight(null)) / 2;
mg.drawImage(sourceImage, x, y, null);
mg.setComposite(AlphaComposite.getInstance(method));
mg.drawImage(maskImage, 0, 0, null);
mg.dispose();
}
return maskedImage;
}
}
The basic work flow follows something like this:
- Create a
BufferedImagewhich represents the shape you want to apply a glow to (this is a opaque image) - Create a "mask" image, which is larger then the image you want to generate a glow effect around, based on the
sizeparameter, but which has the original image painted to it in the center - Use the "mask" image to generate a "blur" image
- Using the original image, mask it to the "blur" image, so that the original image is "cut out" of the "blur" image. This becomes the bases for our glow effect
- Paint the "glow/blur" image, adjusting the x/y position accordingly (the glow effect is larger then the original shape, so we need to adjust it's position)
- Paint the rectangle at the desired location
You'll want to have a look at Compositing Graphics for more details about how the masking process works.
I use this kind of idea to generate drop shadows for transparent/no-rectangular shapes, for example, example and example
来源：https://stackoverflow.com/questions/34123731/add-glow-to-a-basic-java-rectangle