code: public void setConstraints( boolean zeroSkew ,
  								boolean principlePointOrigin ,
  								boolean knownAspect,
  								double aspect )
  	{
  		if( knownAspect && !zeroSkew )
  			throw new IllegalArgumentException("If aspect is known then skew must be zero");
  
  		this.zeroSkew = zeroSkew;
  		this.principlePointOrigin = principlePointOrigin;
  		this.knownAspectRatio = knownAspect;
  		this.aspectRatio = aspect;
  
  		notZeros.resize(6);
  		for (int i = 0; i < 6; i++) {
  			notZeros.data[i] = i;
  		}
  		if( principlePointOrigin ) {
  			notZeros.remove(4);
  			notZeros.remove(2);
  		}
  
  		if( zeroSkew ) {
  			notZeros.remove(1);
  		}
  	}
docs: Specifies linear constraints
  
  Known aspect ratio constraint can only be used if zero skew is also assumped.
  
  @param zeroSkew Assume that skew is zero
  @param principlePointOrigin Principle point is at the origin
  @param knownAspect that the aspect ratio is known
  @param aspect If aspect is known then this is the aspect. ratio=fy/fx Ignored otherwise.