http://xmlgraphics.apache.org/commons/: Apache XML Graphics Commons is a library that consists of several reusable components used by Apache Batik and Apache FOP. Many of these components can easily be used separately outside the domains of SVG and XSL-FO. (Apache Software Foundation) 
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 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
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/* $Id: ImagePreloader.java 750116 2009-03-04 19:23:59Z jeremias $ */

package org.apache.xmlgraphics.image.loader.spi;

import java.io.IOException;

import javax.xml.transform.Source;

import org.apache.xmlgraphics.image.loader.ImageContext;
import org.apache.xmlgraphics.image.loader.ImageException;
import org.apache.xmlgraphics.image.loader.ImageInfo;


This interface provides two functions: determining whether an image format is supported and if
that's the case, some minimal information (mostly the image's intrinsic size) is extracted
and returned.

/**
 * This interface provides two functions: determining whether an image format is supported and if
 * that's the case, some minimal information (mostly the image's intrinsic size) is extracted
 * and returned.
 */
public interface ImagePreloader {

    
Default priority for preloaders 
/** Default priority for preloaders */
    int DEFAULT_PRIORITY = 1000;

    
"Preloads" an image, i.e. indentifies whether the source image is supported by this implementation and determines the image's intrinsic size and possibly some additional information. The image is usually not fully loaded at this time to conserve memory. The method returns null if the image was not identified. An ImageException is only thrown if the image is identified but some error has happened while working on the file. 
Params:
  • originalURI – the original (unresolved) URI of the image
  • src – a image source the image is loaded from
  • context – the context object that provides configuration information
Throws:
  • ImageException – if an error occurs while preloading the image
  • IOException – if an I/O error occurs while preloading the image
Returns:an image info object with the basic information about an image or null if the
          image is not supported by this implementation
/**
     * "Preloads" an image, i.e. indentifies whether the source image is supported by this
     * implementation and determines the image's intrinsic size and possibly some additional
     * information. The image is usually not fully loaded at this time to conserve memory.
     * The method returns null if the image was not identified. An {@link ImageException} is only
     * thrown if the image is identified but some error has happened while working on the file.
     * @param originalURI the original (unresolved) URI of the image
     * @param src a image source the image is loaded from
     * @param context the context object that provides configuration information
     * @return an image info object with the basic information about an image or null if the
     *           image is not supported by this implementation
     * @throws ImageException if an error occurs while preloading the image
     * @throws IOException if an I/O error occurs while preloading the image
     */
    ImageInfo preloadImage(String originalURI,
            Source src, ImageContext context) throws ImageException, IOException;

    
Returns the priority of the preloader. The lower the value, the higher the preloader's
priority.

Returns:an integer (default is 1000)
/**
     * Returns the priority of the preloader. The lower the value, the higher the preloader's
     * priority.
     * @return an integer (default is 1000)
     */
    int getPriority();
}