I found the problem does  happen not only on OPENGL, but also on P3d. I have modified the code to the following. if I set the org_opengl to false, it seems fine; however, if I set the org_opengl to ture, the texture is distorted.

Is the processing bug??

Plz help

=======================================================
import processing.opengl.*;  
import javax.media.opengl.*;  
import com.sun.opengl.util.texture.*;  
boolean org_opengl=true;

Texture tex;  
PImage ti;
void setup()  
{  
 size(480,320, OPENGL);  
 if(org_opengl)
 {
   ti = loadImage("test.png");
   textureMode(NORMALIZED);
 } else  
 {
   try { tex=TextureIO.newTexture(new File(dataPath("test.png")),true); }  
   catch(Exception e) { println(e); }  
 }
}  

void draw()  
{  
 background(0);  

 // the texture size is 300x300
 if(org_opengl)
 {
   beginShape();
   texture(ti);
   vertex(290, 160, 1, 0.5);  
   vertex(265, 205, 236.0/300.0, 1);  
   vertex(215, 205, 64.0/300.0, 1);
   vertex(190, 160, 0, 0.5);  
   vertex(215, 115, 64.0/300.0, 0);  
   vertex(265, 115, 236.0/300.0, 0);  
   endShape();
 } else
 {
   PGraphicsOpenGL pgl = (PGraphicsOpenGL) g;  
   GL gl = pgl.beginGL();  

   tex.bind();  
   tex.enable();  

   gl.glBegin(GL.GL_POLYGON);  
   gl.glNormal3f( 0.0f, 0.0f, 1.0f);  
   gl.glTexCoord2f(1, 0.5);    gl.glVertex2f(290, 160);  
   gl.glTexCoord2f(236.0/300.0, 1); gl.glVertex2f(265, 205);  
   gl.glTexCoord2f(64.0/300.0, 1);  gl.glVertex2f(215, 205);  
   gl.glTexCoord2f(0, 0.5);    gl.glVertex2f(190, 160);  
   gl.glTexCoord2f(64.0/300.0, 0);  gl.glVertex2f(215, 115);  
   gl.glTexCoord2f(236.0/300.0, 0); gl.glVertex2f(265, 115);  
   gl.glEnd();    

   tex.disable();  

   pgl.endGL();  
 }
}