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
* defined in <code>DesignChoiceConstants</code>:
	 * 
	 * <p>
	 * <ul>
	 * <li><code>IMAGE_SIZE_SIZE_TO_IMAGE</code>
	 * <li><code>IMAGE_SIZE_SCALE_TO_ITEM</code>
	 * <li><code>IMAGE_SIZE_CLIP</code>
	 * </ul>
	 * 
	 * @param size
	 *            the size value to be set.
	 * @throws SemanticException
	 *             if the input size is not one of the above, or if the property
	 *             is locked.
	 */
	public void setSize( String size ) throws SemanticException
	{
		setStringProperty( ImageItem.SIZE_PROP, size );
	}
	/**
	 * Sets the type expression value. The source type is automatically set to
	 * <code>IMAGE_REF_TYPE_EXPR</code>.
	 * 
	 * @param value
	 *            the type expression value.
	 * @throws SemanticException
	 *             if the property is locked.
	 */
	public void setTypeExpression( String value ) throws SemanticException
	{