Bug 212246 Browsers keep poping up when click the series with interactivity Focus-Hyperlink [13]
chart/org.eclipse.birt.chart.device.extension/src/org/eclipse/birt/chart/device/image/JavaxImageIOWriter.java
/**
	 * Returns the output image type for this writer.
	 * 
	 * @see java.awt.image.BufferedImage#TYPE_INT_RGB
	 * @see java.awt.image.BufferedImage#TYPE_INT_ARGB
	 * @see java.awt.image.BufferedImage#TYPE_INT_ARGB_PRE
	 * @see java.awt.image.BufferedImage#TYPE_INT_BGR
	 * @see java.awt.image.BufferedImage#TYPE_3BYTE_BGR
	 * @see java.awt.image.BufferedImage#TYPE_4BYTE_ABGR
	 * @see java.awt.image.BufferedImage#TYPE_4BYTE_ABGR_PRE
	 * @see java.awt.image.BufferedImage#TYPE_BYTE_GRAY
	 * @see java.awt.image.BufferedImage#TYPE_USHORT_GRAY
	 * @see java.awt.image.BufferedImage#TYPE_BYTE_BINARY
	 * @see java.awt.image.BufferedImage#TYPE_BYTE_INDEXED
	 * @see java.awt.image.BufferedImage#TYPE_USHORT_565_RGB
	 * @see java.awt.image.BufferedImage#TYPE_USHORT_555_RGB
	 * 
	 * @return
	 */
	protected abstract int getImageType( );
	
	/**
	 * Returns true if the image type supports transparency
	 * false otherwise
	 * @return
	 */
	protected boolean supportsTransparency( )
	{
		return true;
	}