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The main module contains the GeoTools public interfaces that are used by other GeoTools modules (and GeoTools applications). Where possible we make use industry standard terms as provided by OGC and ISO standards. The formal GeoTools public api consists of gt-metadata, jts and the gt-main module. The main module contains the default implementations that are available provided to other GeoTools modules using our factory system. Factories are obtained from an appropriate FactoryFinder, giving applications a chance configure the factory used using the Factory Hints facilities. FilterFactory ff = CommonFactoryFinder.getFilterFactory(); Expression expr = ff.add( expression1, expression2 ); If you find yourself using implementation specific classes chances are you doing it wrong: Expression expr = new AddImpl( expression1, expressiom2 );

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/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2002-2008, Open Source Geospatial Foundation (OSGeo)
 *
 *    This library is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU Lesser General Public
 *    License as published by the Free Software Foundation;
 *    version 2.1 of the License.
 *
 *    This library is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *    Lesser General Public License for more details.
 *
 */
package org.geotools.styling;

import java.awt.Color;
import org.geotools.filter.ConstantExpression;
import org.opengis.filter.expression.Expression;
import org.opengis.style.StyleVisitor;

/**
 * The Fill object encapsulates the graphical-symbolization parameters for areas of geometries.
 *
 * There are two types of fill: solid-color and repeated graphic fill.
 *
 * 
The details of this object are taken from the OGC Styled-Layer Descriptor
 * Report (OGC 02-070) version 1.0.0.:
 *
 * 

 * <xsd:element name="Fill">
 *   <xsd:annotation>
 *     <xsd:documentation>
 *       A "Fill" specifies the pattern for filling an area geometry.
 *       The allowed CssParameters are: "fill" (color) and "fill-opacity".
 *     </xsd:documentation>
 *   </xsd:annotation>
 *   <xsd:complexType>
 *     <xsd:sequence>
 *       <xsd:element ref="sld:GraphicFill" minOccurs="0"/>
 *       <xsd:element ref="sld:CssParameter" minOccurs="0"
 *                    maxOccurs="unbounded"/>
 *     </xsd:sequence>
 *   </xsd:complexType>
 * </xsd:element>
 * 
 *
 * Renderers can use this information when displaying styled features, though it must be
 * remembered that not all renderers will be able to fully represent strokes as set out by this
 * interface. For example, opacity may not be supported.
 *
 * 
Notes:
 *
 * 

 *   The graphical parameters and their values are derived from SVG/CSS2 standards with names
 *       and semantics which are as close as possible.
 * 
 *
 * @author James Macgill, CCG
 * @version $Id$
 */
public interface Fill extends org.opengis.style.Fill {
    static final Fill DEFAULT =
            new ConstantFill() {
                private void cannotModifyConstant() {
                    throw new UnsupportedOperationException("Constant Stroke may not be modified");
                }

                final Expression COLOR = ConstantExpression.color(new Color(128, 128, 128));
                final Expression BGCOLOR = ConstantExpression.color(new Color(255, 255, 255, 0));
                final Expression OPACITY = ConstantExpression.ONE;

                public Expression getColor() {
                    return COLOR;
                }

                public Expression getOpacity() {
                    return OPACITY;
                }

                public Graphic getGraphicFill() {
                    return Graphic.NULL;
                }

                public Object accept(StyleVisitor visitor, Object extraData) {
                    cannotModifyConstant();
                    return null;
                }
            };

    static final Fill NULL =
            new ConstantFill() {
                private void cannotModifyConstant() {
                    throw new UnsupportedOperationException("Constant Stroke may not be modified");
                }

                public Expression getColor() {
                    return ConstantExpression.NULL;
                }

                public Expression getOpacity() {
                    return ConstantExpression.NULL;
                }

                public Graphic getGraphicFill() {
                    return Graphic.NULL;
                }

                public Object accept(StyleVisitor visitor, Object extraData) {
                    cannotModifyConstant();
                    return null;
                }
            };

    /**
     * This parameter gives the solid color that will be used for a Fill.

     * The color value is RGB-encoded using two hexidecimal digits per primary-color component, in
     * the order Red, Green, Blue, prefixed with the hash (#) sign. The hexidecimal digits beetween
     * A and F may be in either upper or lower case. For example, full red is encoded as "#ff0000"
     * (with no quotation marks). The default color is defined to be 50% gray ("#808080"). Note: in
     * CSS this parameter is just called Fill and not Color.
     *
     * @return The color of the Fill encoded as a hexidecimal RGB value.
     */
    Expression getColor();

    /**
     * This parameter gives the solid color that will be used for a Fill.

     * The color value is RGB-encoded using two hexidecimal digits per primary-color component, in
     * the order Red, Green, Blue, prefixed with the hash (#) sign. The hexidecimal digits beetween
     * A and F may be in either upper or lower case. For example, full red is encoded as "#ff0000"
     * (with no quotation marks).
     *
     * @param color solid color that will be used for a Fill
     */
    void setColor(Expression color);

    /**
     * This specifies the level of translucency to use when rendering the fill. 

     * The value is encoded as a floating-point value between 0.0 and 1.0 with 0.0 representing
     * totally transparent and 1.0 representing totally opaque, with a linear scale of translucency
     * for intermediate values.

     * For example, "0.65" would represent 65% opacity. The default value is 1.0 (opaque).
     *
     * @return The opacity of the fill, where 0.0 is completely transparent and 1.0 is completely
     *     opaque.
     */
    Expression getOpacity();

    /**
     * This specifies the level of translucency to use when rendering the fill. 

     * The value is encoded as a floating-point value between 0.0 and 1.0 with 0.0 representing
     * totally transparent and 1.0 representing totally opaque, with a linear scale of translucency
     * for intermediate values.

     * For example, "0.65" would represent 65% opacity.
     */
    void setOpacity(Expression opacity);

    /**
     * This parameter indicates that a stipple-fill repeated graphic will be used and specifies the
     * fill graphic to use.
     *
     * @return The graphic to use as a stipple fill. If null then no stipple fill should be used.
     */
    Graphic getGraphicFill();

    /**
     * This parameter indicates that a stipple-fill repeated graphic will be used and specifies the
     * fill graphic to use.
     */
    void setGraphicFill(org.opengis.style.Graphic graphicFill);

    void accept(org.geotools.styling.StyleVisitor visitor);
}

abstract class ConstantFill implements Fill {
    private void cannotModifyConstant() {
        throw new UnsupportedOperationException("Constant Fill may not be modified");
    }

    public void setColor(Expression color) {
        cannotModifyConstant();
    }

    public void setBackgroundColor(Expression backgroundColor) {
        cannotModifyConstant();
    }

    public void setOpacity(Expression opacity) {
        cannotModifyConstant();
    }

    public void setGraphicFill(org.opengis.style.Graphic graphicFill) {
        cannotModifyConstant();
    }

    public void accept(org.geotools.styling.StyleVisitor visitor) {
        cannotModifyConstant();
    }

    public Object accept(org.opengis.style.StyleVisitor visitor, Object data) {
        cannotModifyConstant();
        return null;
    }
}