Bug 149922 Image builder - URI and file source type are treated as same
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ImageHandle.java
try
		{
			module.getActivityStack( ).startTrans( );
			setProperty( ImageItem.SOURCE_PROP,
					DesignChoiceConstants.IMAGE_REF_TYPE_EXPR );
			setProperty( ImageItem.TYPE_EXPR_PROP, value );
		}
		catch ( SemanticException e )
		{
			module.getActivityStack( ).rollback( );
			throw e;
		}
		module.getActivityStack( ).commit( );
	}
	/**
	 * Sets the value expression value. The source type is automatically set to
	 * <code>IMAGE_REF_TYPE_EXPR</code>.
	 * 
	 * @param value
	 *            the value expression.
	 * @throws SemanticException
	 *             if the property is locked.
	 */
	public void setValueExpression( String value ) throws SemanticException
	{
		try
		{
			module.getActivityStack( ).startTrans( );
			setProperty( ImageItem.SOURCE_PROP,
					DesignChoiceConstants.IMAGE_REF_TYPE_EXPR );