Trishia's code

public abstract class UniversalJPanel extends JPanel{

	protected BufferedImage image;
	protected Graphics2D g2d;

	protected int iterations = 100; // max number of iterations
	protected double realMin = -2.0; // default min real
	protected double realMax = 2.0;// default max real
	protected double imaginaryMin = -1.6; // default min imaginary
	protected double imaginaryMax = 1.6;// default max imaginary
	protected int panelHeight;
	protected int panelWidth;
	protected Point pressed, released; // points pressed and released - used to calculate drawn rectangle
	protected boolean dragged; // if is dragged - draw rectangle
	protected int recWidth, recHeight,xStart, yStart; // variables to calculate rectangle
	protected FractalWorker[] arrayOfWorkers; // array of Swing workers



	public abstract int calculateIterations(Complex c);
	public abstract double getDistance(Complex a, Complex b);

	public void paintComponent(Graphics g){
		super.paintComponent(g);
		panelHeight = getHeight();
		panelWidth = getWidth();
		image =new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB); // creating new Bufered image
		g2d= (Graphics2D) image.getGraphics();



		arrayOfWorkers= new FractalWorker[getHeight()]; // create new worker for each row and execute them
		 for(int q = 0; q < getHeight(); q++ ){
		    	arrayOfWorkers[q] = new FractalWorker(q);
		    	arrayOfWorkers[q].execute();
		}

		g.drawImage(image, 0, 0, image.getWidth(), image.getWidth(), null); // draw an image

	}

// *** getters, setters, different code//

private class FractalWorker extends SwingWorker<Object, Object>{
	private int y;	// row on which worker should work now
	private Color[] arrayOfColors; // array of colors produced by workers
	public FractalWorker( int z){
		y = z;
	}
	protected Object doInBackground() throws Exception {

		arrayOfColors = new Color[getWidth()];

		for(int q=0; q<getWidth(); q++){ // calculate and insert into array proper color for given pixel
			int iter = calculateIterations(setComplexNumber(new Point(q,y)));
			if(iter == iterations){
				arrayOfColors[q] = Color.black;
			}else{
				arrayOfColors[q] = Color.getHSBColor((float)((iter/ 20.0)), 1.0f, 1.0f );
			}
		}
		return null;
	}
	protected void done(){ // take color from the array and draw pixel
		for(int i = 0; i<arrayOfColors.length; i++){
			g2d.setColor(arrayOfColors[i]);
			g2d.drawLine(i, y, i, y);
		}
	}

}