/* Sample Java program for image display  
 Bilinear Interpolation of colors   by T.Nishita 
*/
import java.applet.*;
import java.awt.*;
import java.awt.image.*;

public class bilinear extends Applet implements Runnable {
    Dimension appsize;
    Button b1;
    int  xres=380, yres=320;
    Image imageBuffer;
    Graphics GR;
    Thread thread = null; 
	Color C = Color.darkGray;
	Color C00,C01,C11,C10;
	int index=0;

public void init() {
//	setLayout(new BorderLayout(0,0)); Panel p = new Panel();
	add(b1 = new Button("Display")); // p.add(b1 = new Button("Display"));
//  p.setBackground(Color.blue);  add("North",p);

    imageBuffer = createImage(size().width, size().height);
    GR = imageBuffer.getGraphics();
    setBackground(Color.lightGray);
    resize(size());
	xres = size().width-50; yres = size().height-70;
	index=9;
}
public boolean action(Event e, Object o) {
    if (e.target == b1) {  // Check Draw_button
	stop(); index++;
	start();
    }
    return true;
}
public void start() {
    if (thread == null) {
	thread = new Thread(this);
	thread.start();
    }
}
public void stop() {
    if(thread != null) {
	thread.stop();
	thread = null;
    }
}
public void update(Graphics g) {
    g.drawImage(imageBuffer, 0, 0, this);
}
public void paint(Graphics g) {
    update(g);
}
public void run() {
	// set colors at the corneres
      C00 = col16(index++%16);
      C10 = col16(index++%16);
      C11 = col16(index++%16);
      C01 = col16(index++%16);

      for (int iy =35; iy<yres+35; iy++)   {
		  double v = (double)(iy-35)/(double)(yres);
        for (int ix =20; ix<xres+20; ix++) {
			double u = (double)(ix-20)/(double)(xres);
			Color C =  Clinear(u,v);
			GR.setColor(C); //	GR.setColor(col16((iy+ix+index)%16));
			GR.drawLine(ix,iy, ix, iy); }
 		repaint();
      }

	GR.setColor(Color.black);
	GR.drawString(" C00= (" + C00.getRed()+"."+C00.getGreen()+","+C00.getBlue()+")", 25,50); 
	GR.drawString(" C10= (" + C10.getRed()+"."+C10.getGreen()+","+C10.getBlue()+")", xres-80,50); 
	GR.drawString(" C01= (" + C01.getRed()+"."+C01.getGreen()+","+C01.getBlue()+")", 25,yres+30); 
	GR.drawString(" C11= (" + C11.getRed()+"."+C11.getGreen()+","+C11.getBlue()+")", xres-80,yres+30); 
 
	GR.drawImage(imageBuffer, 0, 0, null);
    thread = null;
}
	public  Color Clinear(double u, double v){

		if(u<0.) u= 0.; if(u>1.) u=1.0;
		if(v<0.) v= 0.; if(v>1.) v=1.0;
	  double red =((1.-u)*(double)C00.getRed() 
			+ u*(double)C10.getRed())*(1-v)
			+ ((1.-u)*(double)C01.getRed()
			+ u*(double)C11.getRed())*v;
	  double green = ((1.-u)*(double)C00.getGreen() 
			+ u*(double)C10.getGreen())*(1-v)
			+((1.-u)*(double)C01.getGreen()
			+ u*(double)C11.getGreen())*v;
	   double blue = ((1.-u)*(double)C00.getBlue() 
			+ u*(double)C10.getBlue())*(1-v)
			+ ((1.-u)*(double)C01.getBlue()
			+ u*(double)C11.getBlue())*v;
		return new Color((int)red,(int)green,(int)blue);
	}
// Colors used in Dos 16-color Display
	public  Color col16(int i){
		int code[][] ={
			{0,0,0},
			{0,0,168},
			{0,168,0},
			{0,168,168},
			{168,0,0},
			{168,0,168},
			{168,84,0},
			{168,168,168},
			{84,84,84},
			{84,84,255},
			{84,255,84},
			{84,255,255},
			{255,84,84},
			{255,84,255},
			{255,255,84},
			{255,255,255}		};
     return new Color(code[i][0],code[i][1],code[i][2]);
	}
	public boolean mouseDown(Event ev, int x, int y) {
		double v = (double)(y-35)/(double)(yres);
		double u = (double)(x-20)/(double)(xres);
		Color C =  Clinear(u,v);
		GR.setColor(C); 
		GR.fillRect(27,yres+40, 85, 22); 
		GR.setColor(Color.black);
 		GR.drawString(" C=(" + C.getRed()+"."+C.getGreen()+","+C.getBlue()+")", 25,yres+53); 
 		repaint();
		return true;
	}
}