Anisotropic and Isotropic Mapping Modes
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The term anisotropic mapping implies that the scale factors for x and y are
not necessarily equal. Consider the following code fragment:
<![CDATA[
Dimension d = getSize();
int rWidth = 100;
int rHeight = 100;
int maxX = d.width - 1; maxY = d.height - 1;
float pixelWidth = rWidth/maxX;
float pixelHeight = rHeight/maxY;
...
int iX(float x){return Math.round(x/pixelWidth);}
int iY(float y){return Math.round(y/pixelHeight);}
float fx(int X){return X * pixelWidth;}
float fy(int Y){return (maxY - Y) * pixelHeight;}
]]>
As you can see, the values of pixelWidth and pixelHeight are a function of
the dimensions of the drawing area.
In isotropic mapping, the scale factors for x and y are equal. Further, it
is often the case in isotropic mapping mode that the center of the draw area
be defined as (0,0). Here's a code fragment which defines coordinates in
isotropic mapping mode with the center of the draw area at (0,0).
<![CDATA[
Dimension d = getSize();
int maxX = d.width -1, maxY = d.height -1;
float pixelSize = Math.max(rWidth/maxX, rHeight/maxY);
int centerX = maxX/2;
int centerY = maxY/2;
...
int iX(float x){return Math.round(centerX + x/pixelSize);}
int iY(float y){return Math.round(centerY - y/pixelSize);}
float fx(int X){return (X - centerX) * pixelSize;}
float fy(int Y){return (centerY - Y) * pixelSize;}
]]>
Here's an applet which uses isotropic mapping mode:
<![CDATA[
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class Isotrop extends Applet{
public void init(){
setBackground(Color.white);
setLayout(new BorderLayout());
add("Center", new CvIsotrop() );
}
}
class CvIsotrop extends Canvas{
int centerX, centerY;
float pixelSize, rWidth = 10.0F, rHeight = 10.0F, xP = 1000000, yP;
CvIsotrop(){
addMouseListener(new MouseAdapter(){
public void mousePressed(MouseEvent me){
xP = fx(me.getX());
yP = fy(me.getY());
repaint();
}
});
}
void initgr(){
Dimension d = getSize();
int maxX = d.width-1, maxY = d.height-1;
pixelSize = Math.max(rWidth/maxX, rHeight/maxY);
centerX = maxX/2; centerY = maxY/2;
}
int iX(float x){return Math.round(centerX + x/pixelSize);}
int iY(float y){return Math.round(centerY - y/pixelSize);}
float fx(int X){return (X - centerX) * pixelSize;}
float fy(int Y){return (centerY - Y) * pixelSize;}
public void paint(Graphics g){
initgr();
int left = iX(-rWidth/2), right = iX(rWidth/2),
bottom = iY(-rHeight/2), top = iY(rHeight/2),
xMiddle = iX(0), yMiddle = iY(0);
g.drawLine(xMiddle, bottom, right, yMiddle);
g.drawLine(right, yMiddle, xMiddle, top);
g.drawLine(xMiddle, top, left, yMiddle);
g.drawLine(left, yMiddle, xMiddle, bottom);
if(xP != 1000000)
g.drawString("Logical coordinates of selected point: "
+ xP + ", " + yP, 20, 100);
}
}
//<applet code=Isotrop.java width=300 height=300></applet>
]]>
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ASSIGNMENT:
| Recreate this applet. Supply drawing methods with variables derived from
isotropic values only. Click on it to make sure you are fully aware of what
it does.
|
|