setBorder(BorderFactory.createTitledBorder("Coordinate Transformation"));
int x = 8;
int y = 8+20;
Matrix3x3 m = mat.getMatrix();
for (int i = 0; i < 9; i++) {
fields[i] = new JTextField(""+m.get(i));
fields[i].setBounds(x, y, 40, h);
add(fields[i]);
fields[i].getDocument().addDocumentListener(this);
if ((i%3)==2) {x = 8; y += h;}
else x += 42;