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Gradient problems in Java

由 南笙酒味 提交于 2019-12-18 19:13:11

问题


In my program I wanted to have a translucent white to transparent gradient on my JFrame to overlay a yellow background. This works fine and it needs to be a white to transparent because of how my settings for the program work for the user. However, when I take the program into college (JRE7 to my JRE6) the gradient goes white to blackish then transparent... It isn't so bad until you start to increase the opacity of the white colour... is there anyway I can fix this?

here is the relevant code from the top of my JFrame code.

public class DictionaryGUI extends JFrame
{   
    protected JPanel pGradientPane;

    //Interface gradient specification
    private Color pInterfaceColour = new Color(255, 245, 62);
    protected int iDegreeWhite = 180
    protected int iDegreeBlack = 0

    DictionaryGUI(int iWidth, int iHeight)
    {
        /*General definitions*/
        super(String.format("French Verb Conjugator - Version %s", MainLauncher.version));
        setSize(iWidth, iHeight);
        new Menu(this);

        this.iWidth = iWidth;    
        this.iHeight = iHeight;

        getContentPane().setBackground(pInterfaceColour);
        pGradientPane = new JPanel(new GridBagLayout())
        {
            private static final long serialVersionUID = 1L;

            protected void paintComponent(Graphics pGraphics) 
            {
                Graphics2D pGraphicsGradientRender = (Graphics2D) pGraphics;
                pGraphicsGradientRender.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
                GradientPaint pGradient = new GradientPaint(0, 0, new Color(255, 255, 255, iDegreeWhite), 0, getHeight(), new Color(0, 0, 0, iDegreeBlack));
                pGraphicsGradientRender.setPaint(pGradient);
                pGraphicsGradientRender.fillRect(0, 0, getWidth(), getHeight());
                super.paintComponent(pGraphics);
            }
        };
        pGradientPane.setOpaque(false);
        pGradientPane.setPreferredSize(new Dimension(iWidth - 16, iHeight - 62));
        /*components added to pGradientPane here!*/
        add(pGradientPane);
    }

And the mainclass aswell:

public class MainLauncher
{
    static int iHeight = 400;
    static int iWidth = 730;
    static String version = "0A3B6";

    public static void main(String[] args)
    {
    try 
    {
        for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels())
        {
            if ("Nimbus".equals(info.getName()))
            {
                UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (Exception e) {e.printStackTrace();}
    DictionaryGUI window = new DictionaryGUI(iWidth, iHeight);
    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    window.setLocationByPlatform(true);
    window.setVisible(true);
}

Is it just some difference between JRE6 and JRE7? should I make the bottom colour to white aswell? (was black incase people want to darken the colour at the bottom.)

I can post some screenshots tommorrow if anybody needs them....

Thanks Jamie

EDIT: I changed the second (transparent) colour in the gradient to white and it fixes the problem. However, I am still troubled to why the transparent black colour shows through in the middle? it must be something to do with JRE7 because thats where it occurs... maybe they changed something with how transparency in gradients work. Does anybody know how to eliminate this problem while keeping the colour black?


回答1:


The problem with the code is this line:

GradientPaint pGradient = new GradientPaint(0, 0, new Color(255, 255, 255, iDegreeWhite), 0, getHeight(), new Color(0, 0, 0, iDegreeBlack));

should be this:

GradientPaint pGradient = new GradientPaint(0, 0, new Color(255, 255, 255, iDegreeWhite), 0, getHeight(), new Color(255, 245, 62, iDegreeWhite));

Looking back at your question, I see you've basically found the solution - but it's a little different. Here's why:

When blending the colors in the gradient, your blending all aspects of the color: RBGA

You see, until you reach the full second color, you are mixing black into the color gradient and that mix won't be at the full transparency. So 20% of the way down the page, you'll have this color: 204,204,204,144 (that's 80% white, 20% black, and 56% opaque).

The easiest solution is to avoid translucency completely if you're not using it - just blend from the light yellow at the top to the dark yellow at the bottom. It takes less resources this way too.

But since you're using transparency, the solution I've provided uses transparency as well. You'll be blending from the white to the yellow using a consistent transparency.

If you blend from white to white (transparent), you'll have the same problem as before only with white (which will be less noticeable since it's one of the colors you're using): The gradient will have a white "streak" until the second color reaches full transparency.

As far as why it acts different on different JVMs, I'd guess that Oracle may have changed the way alpha's are blended. Better alpha support seems to be something they've been working on for a while, and this is a logical step in that direction. I don't have any proof on this statement though - it's just based on other changes I've seen with alpha's (like transparent windowing).

EDIT This SSCCE demos both the problem and the solution:

import java.awt.*;
import javax.swing.*;
import javax.swing.UIManager.LookAndFeelInfo;


public class TransparencyDemo extends Box{

    protected JPanel pGradientPane;

    //Interface gradient specification
    private Color pInterfaceColour = new Color(255, 245, 62);
    protected int iDegreeWhite = 180;
    protected int iDegreeBlack = 0;

    public TransparencyDemo() {
        super(BoxLayout.X_AXIS);
        setOpaque(true);

        //Incorrect Solution
        pGradientPane = new JPanel(new GridBagLayout())
        {
            private static final long serialVersionUID = 1L;

            protected void paintComponent(Graphics pGraphics) 
            {
                Graphics2D pGraphicsGradientRender = (Graphics2D) pGraphics;
                pGraphicsGradientRender.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
                GradientPaint pGradient = new GradientPaint(0, 0, new Color(255, 255, 255, iDegreeWhite), 0, getHeight(), new Color(0, 0, 0, iDegreeBlack));
                pGraphicsGradientRender.setPaint(pGradient);
                pGraphicsGradientRender.fillRect(0, 0, getWidth(), getHeight());
                super.paintComponent(pGraphics);
            }
        };
        pGradientPane.setOpaque(false);
        add(pGradientPane);

        //Correct Solution
        JPanel pGradientPane2 = new JPanel(new GridBagLayout())
        {
            private static final long serialVersionUID = 1L;

            protected void paintComponent(Graphics pGraphics) 
            {
                Graphics2D pGraphicsGradientRender = (Graphics2D) pGraphics;
                pGraphicsGradientRender.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
                GradientPaint pGradient = new GradientPaint(0, 0, new Color(255, 255, 255, iDegreeWhite), 0, getHeight(),  new Color(255, 245, 62, iDegreeWhite));
                pGraphicsGradientRender.setPaint(pGradient);
                pGraphicsGradientRender.fillRect(0, 0, getWidth(), getHeight());
                super.paintComponent(pGraphics);
            }
        };
        pGradientPane2.setOpaque(false);
        add(pGradientPane2);


        setBackground(pInterfaceColour);

    }

    public static void main(String[] args){
        try {
             for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                   UIManager.setLookAndFeel(info.getClassName());
                   break;
                }
             }
          } catch (Exception e) {
             e.printStackTrace();
          }

        final JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(new TransparencyDemo());
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}



回答2:


Here is my version of your code as an sscce:

import java.awt.*;
import javax.swing.*;
import javax.swing.UIManager.LookAndFeelInfo;

public class MainLauncher {
   static int iHeight = 400;
   static int iWidth = 730;
   static String version = "0A3B6";

   public static void main(String[] args) {
      try {
         for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
               UIManager.setLookAndFeel(info.getClassName());
               break;
            }
         }
      } catch (Exception e) {
         e.printStackTrace();
      }
      DictionaryGUI window = new DictionaryGUI(iWidth, iHeight);
      window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      window.setLocationByPlatform(true);
      window.setVisible(true);
   }

}

class DictionaryGUI extends JFrame {
   protected JPanel pGradientPane;

   // Interface gradient specification
   private Color pInterfaceColour = new Color(255, 245, 62);
   protected int iDegreeWhite = 180;
   protected int iDegreeBlack = 0;

   DictionaryGUI(int iWidth, int iHeight) {
      /* General definitions */
      super(String.format("French Verb Conjugator - Version %s",
            MainLauncher.version));
      setSize(iWidth, iHeight);

      getContentPane().setBackground(pInterfaceColour);
      pGradientPane = new JPanel() {
         private static final long serialVersionUID = 1L;

         protected void paintComponent(Graphics pGraphics) {
            Graphics2D pGraphicsGradientRender = (Graphics2D) pGraphics;
            pGraphicsGradientRender.setRenderingHint(
                  RenderingHints.KEY_ANTIALIASING,
                  RenderingHints.VALUE_ANTIALIAS_ON);
            GradientPaint pGradient = new GradientPaint(0, 0, new Color(255,
                  255, 255, iDegreeWhite), 0, getHeight(), new Color(0, 0, 0,
                  iDegreeBlack));
            pGraphicsGradientRender.setPaint(pGradient);
            pGraphicsGradientRender.fillRect(0, 0, getWidth(), getHeight());
            super.paintComponent(pGraphics);
         }
      };
      pGradientPane.setOpaque(false);
      pGradientPane.setPreferredSize(new Dimension(iWidth - 16, iHeight - 62));
      /* components added to pGradientPane here! */
      add(pGradientPane);
   }
}

But again this doesn't demonstrate your problem. I'm guessing though that your problem is one of using transparent backgrounds with Swing GUI where painting artifacts are not corrected fully. If so, please read what Rob Camick has to say about this on his blog: Backgrounds With Transparency




回答3:


My guess is that it's about the 'graphics pipeline' that's being used on the different computers.

Java has several different pipelines, here is some information about them.

On my computer I can use the X11 pipeline, or the OpenGL pipeline. With the X11 pipeline the darkness occurs; on OpenGL, it doesn't.

On Windows you can choose from 3 different pipelines, and even then (looking at the link above), there can be differences.

I can't immediately imagine what's the configuration your school has, and why it's different, but you can try to investigate.

You might want to file this difference as a bug.




回答4:


I have got fatamorgana, I'm sure that GradientPaint is darker and darker and darker, phaaa crazy eye illusion, brrrr

//http://stackoverflow.com/questions/13748810/gradient-problems-in-java/13806210#comment18995490_13806210

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Container;
import java.awt.EventQueue;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.RepaintManager;
import javax.swing.UIManager;
import javax.swing.UIManager.LookAndFeelInfo;

public class MainLauncher {

    private JFrame window = new JFrame();

    public MainLauncher() {
        GradientPane pane = new GradientPane();
        pane.setLayout(new GridLayout(6, 4, 15, 15));
        for (int i = 1; i <= 24; i++) {
            pane.add(createButton(i));
        }
        pane.setOpaque(false);
        window.add(pane);
        RepaintManager.setCurrentManager(new RepaintManager() {

            @Override
            public void addDirtyRegion(JComponent c, int x, int y, int w, int h) {
                Container con = c.getParent();
                while (con instanceof JComponent) {
                    if (!con.isVisible()) {
                        return;
                    }
                    if (con instanceof GradientPane) {
                        c = (JComponent) con;
                        x = 0;
                        y = 0;
                        w = con.getWidth();
                        h = con.getHeight();
                    }
                    con = con.getParent();
                }
                super.addDirtyRegion(c, x, y, w, h);
            }
        });
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setLocationByPlatform(true);
        window.setSize(400, 300);
        //window.pack();
        window.setVisible(true);
    }

    private JButton createButton(final int text) {
        JButton button = new JButton(Integer.toString(text));
        return button;
    }

    class GradientPane extends JPanel {

        private static final long serialVersionUID = 1L;
        private final int h = 150;
        private BufferedImage img = null;
        private BufferedImage shadow = new BufferedImage(1, h, BufferedImage.TYPE_INT_ARGB);

        public GradientPane() {
            paintBackGround(new Color(150, 250, 150));
        }

        public void paintBackGround(Color g) {
            Graphics2D g2 = shadow.createGraphics();
            g2.setPaint(g);
            g2.fillRect(0, 0, 1, h);
            g2.setComposite(AlphaComposite.DstIn);
            g2.setPaint(new GradientPaint(0, 0, new Color(0, 0, 0, 0f), 0, h, new Color(0.1f, 0.8f, 0.8f, 0.5f)));
            g2.fillRect(0, 0, 1, h);
            g2.dispose();
        }

        @Override
        public void paintComponent(Graphics g) {
            if (img == null || img.getWidth() != getWidth() || img.getHeight() != getHeight()) {
                img = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB);
            }
            Graphics2D g2 = img.createGraphics();
            super.paintComponent(g2);
            Rectangle bounds = this.getVisibleRect();
            g2.scale(bounds.getWidth(), -1);
            g2.drawImage(shadow, bounds.x, -bounds.y - h, null);
            g2.scale(1, -1);
            g2.drawImage(shadow, bounds.x, bounds.y + bounds.height - h, null);
            g2.dispose();
            g.drawImage(img, 0, 0, null);
        }
    }

    public static void main(String[] args) {
        try {
            for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                MainLauncher ml = new MainLauncher();
            }
        });
    }
}



回答5:


As Nick pointed out, the problem is that you are using transparent black rather than transparent white. So the translucent colours are a shade between white and black.

Try replacing with this line in your code:

GradientPaint pGradient = new GradientPaint(0, 0, new Color(255, 255, 255, iDegreeWhite), 0, getHeight(), new Color(255, 255, 255, iDegreeBlack));


来源：https://stackoverflow.com/questions/13748810/gradient-problems-in-java

标签
java
swing
nimbus
gradient
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