java - Rotate image without clear background -

i have read lot of articles of drawing images, cant work when need keep background. i'm trying rotate image on image after click on jbutton. background image generated on jpanel by:

public void paintcomponent(graphics g){      int index = 0;      graphics2d g2 = (graphics2d) g;      super.paintcomponent(g);          try {         image = imageio.read(url1);         image2 = imageio.read(url2);         image3 = imageio.read(url3);     } catch (ioexception e) {     }       g.drawimage(image, 0, 0, null);     g.drawimage(image3, 0, 0, null);      if(scaledrawnflag == 0){          for(index = 0; index < 60; index ++){             tx = affinetransform.getrotateinstance(math.toradians(6*index), this.getheight()/2, this.getwidth()/2);             op = new affinetransformop(tx, affinetransformop.type_bilinear);             g.drawimage(op.filter(image3, null), 0, 0, null);         }                 scaledrawnflag = 1;     }      g.drawimage(image2, 0, 0, null);  } 

which jpanel named panel , draw image 1 time keep refresh performance, animated image. draws scale tachometer, total of 60 lines, each line copy of image3

the animated image, generated pressing jbutton, , made by:

public void paintcomponent(graphics g){      super.paintcomponent(g);             bufferedimage img = new bufferedimage(370, 370, bufferedimage.translucent);     graphics2d g2d = img.creategraphics();     g2d.setcomposite(alphacomposite.getinstance(alphacomposite.clear, 0.0f));     g2d.fillrect(0, 0, img.getwidth(), img.getheight());     g2d.setcomposite(alphacomposite.getinstance(alphacomposite.src_over, 0.0f));     graphics2d temp = (graphics2d) g;     tx = affinetransform.getrotateinstance(math.toradians(degrees), this.getheight()/2, this.getwidth()/2);     op = new affinetransformop(tx, affinetransformop.type_bilinear);     temp.drawimage(op.filter(image2, null), 0, 0, null);     temp.dispose(); } 

which jpanel named overpanel, on initial jpanel.

but, when call methods:

public void up(){     degrees ++;     if(degrees == 360) degrees = 0;     repaint(); }  public void down(){     degrees --;     if(degrees == -360) degrees = 0;     repaint(); } 

which on overpanel class, jpanel entirely cleared. animation working but, background disappear.

what must keep background?

i tried solution, drawing 60 lines again on every up() , down() call. background repainted, takes time complete, so, animation rotate tachometer's indicator lags.

never dispose of graphics object given jvm. you're doing this:

// temp **is** same object g , graphics object given jvm graphics2d temp = (graphics2d) g;  //.... temp.dispose(); 

and shouldn't since breaks painting chain. should instead disposing of g2d object, 1 created.

also, ok

graphics2d temp = (graphics2d) g.create(); // temp **is** new object //.... temp.dispose();  // ok 

other issues:

• i wouldn't creating bufferedimage inside of paintcomponent rather make field of class, , display inside paintcomponent.
• your top code shows ignored critical exceptions -- don't want this.
• it shows reading in of image files within painting method, unnecessarily slow down graphics. again, don't this, read in images once outside of painting method, store results, , use them in painting method.
• the paintcomponent method protected, not public. avoid increasing visibility unnecessarily.

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in minimal example program, scaledrawnflag variable , associated if-block appear messing up. purpose of variable , if block? if rid of variable , if block, background persist. myself, i'd things differently creating stable background image , drawing every time in paintcomponent(...) method. not override update(...) either that's awt kludge , not swing graphics. try avoid null layouts , setbounds(...) plague since leads inflexible, rigid gui's difficult debug, maintain , enhance. example:

import java.awt.borderlayout; import java.awt.dimension; import java.awt.graphics; import java.awt.graphics2d; import java.awt.gridlayout; import java.awt.renderinghints; import java.awt.event.actionevent; import java.awt.event.keyevent; import java.awt.geom.affinetransform; import java.awt.image.affinetransformop; import java.awt.image.bufferedimage; import java.io.ioexception; import java.net.url;  import javax.imageio.imageio; import javax.swing.*;  @suppresswarnings("serial") public class mymainpanel extends jpanel {    private mydrawingpanel mydrawingpanel;     public mymainpanel() {       try {          mydrawingpanel = new mydrawingpanel();       } catch (ioexception e) {          e.printstacktrace();          system.exit(-1);       }        jpanel rightpanel = new jpanel();       rightpanel.setlayout(new gridlayout(0, 1, 5, 5));       rightpanel.add(new jbutton(new myupaction("up", keyevent.vk_u)));       rightpanel.add(new jbutton(new mydownaction("down", keyevent.vk_d)));        jpanel rightwrappanel = new jpanel(new borderlayout());       rightwrappanel.add(rightpanel, borderlayout.page_start);        setborder(borderfactory.createemptyborder(5, 5, 5, 5));       setlayout(new borderlayout());       add(mydrawingpanel, borderlayout.center);       add(rightwrappanel, borderlayout.line_end);    }     private class myupaction extends abstractaction {       public myupaction(string name, int mnemonic) {          super(name);          putvalue(mnemonic_key, mnemonic);       }        @override       public void actionperformed(actionevent e) {          mydrawingpanel.up();       }    }     private class mydownaction extends abstractaction {       public mydownaction(string name, int mnemonic) {          super(name);          putvalue(mnemonic_key, mnemonic);       }        @override       public void actionperformed(actionevent e) {          mydrawingpanel.down();       }    }     private static void createandshowgui() {       jframe frame = new jframe("mymainpanel");       frame.setdefaultcloseoperation(jframe.exit_on_close);       frame.getcontentpane().add(new mymainpanel());       frame.pack();       frame.setlocationrelativeto(null);       frame.setvisible(true);    }     public static void main(string[] args) {       swingutilities.invokelater(new runnable() {          public void run() {             createandshowgui();          }       });    } }  @suppresswarnings("serial") class mydrawingpanel extends jpanel {    private static final string needle_img_path = "http://1.bp.blogspot.com/"          + "-fq-opgbslp4/ttoj7doamwi/aaaaaaaabtc/t7gkjlfrquo/s400/secondhand.png";    private static final string orange_disk_img_path = "http://upload.wikimedia.org/wikipedia/commons/thumb/b/b6/circle_fulvous_solid.svg/200px-circle_fulvous_solid.svg.png";    private static final string green_line_img_path = "http://www.xtremeskater.com/math/images/circle_radius.png";    private static final int max_degrees = 360;     private int imgwidth = 0;    private int imgheight = 0;    private bufferedimage needleimg = null;    private bufferedimage orangediskimg = null;    private bufferedimage greenlineimg = null;    private bufferedimage backgroundimg = null;    private int degrees;      public mydrawingpanel() throws ioexception {       url needleurl = new url(needle_img_path);       url orangediskurl = new url(orange_disk_img_path);       url greenlineurl = new url(green_line_img_path);       needleimg = imageio.read(needleurl);       orangediskimg = imageio.read(orangediskurl);       greenlineimg = imageio.read(greenlineurl);        imgwidth = math.max(orangediskimg.getwidth(),              greenlineimg.getwidth());       imgheight = math.max(orangediskimg.getheight(),             greenlineimg.getheight());       backgroundimg = new bufferedimage(imgwidth, imgheight,             bufferedimage.type_int_argb);       graphics2d g2 = backgroundimg.creategraphics();       drawbackground(g2, imgwidth, imgheight);       g2.dispose();    }     @override    public dimension getpreferredsize() {       if (ispreferredsizeset()) {          return super.getpreferredsize();       }       return new dimension(imgwidth, imgheight);    }     @override    protected void paintcomponent(graphics g) {       super.paintcomponent(g);       if (backgroundimg != null) {          g.drawimage(backgroundimg, 0, 0, null);       }       affinetransform tx = affinetransform.getrotateinstance(math.toradians(degrees),             this.getheight() / 2, this.getwidth() / 2);       affinetransformop op = new affinetransformop(tx, affinetransformop.type_bilinear);       g.drawimage(op.filter(needleimg, null), 0, 0, null);    }     public void up() {       degrees++;       degrees %= max_degrees;       repaint();    }     public void down() {       degrees--;       degrees += max_degrees;       degrees %= max_degrees;       repaint();    }     public int getdregrees() {       return degrees;    }     private void drawbackground(graphics2d g2, int biwidth, int biheight) {       int index;       g2.setrenderinghint(renderinghints.key_antialiasing,             renderinghints.value_antialias_on);       g2.drawimage(orangediskimg, 0, 0, null);       g2.drawimage(greenlineimg, 0, 0, null);       affinetransform tx = affinetransform.getrotateinstance(math.toradians(6),             biwidth / 2, biheight / 2);       (index = 0; index < 60; index++) {          g2.transform(tx);          g2.drawimage(greenlineimg, 0, 0, null);       }    } }