ImageIO.java revision 1292
1879N/A * Copyright 2000-2005 Sun Microsystems, Inc. All Rights Reserved. 0N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 0N/A * This code is free software; you can redistribute it and/or modify it 0N/A * under the terms of the GNU General Public License version 2 only, as 0N/A * published by the Free Software Foundation. Sun designates this 0N/A * particular file as subject to the "Classpath" exception as provided 0N/A * by Sun in the LICENSE file that accompanied this code. 0N/A * This code is distributed in the hope that it will be useful, but WITHOUT 0N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 0N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 0N/A * version 2 for more details (a copy is included in the LICENSE file that 0N/A * accompanied this code). 0N/A * You should have received a copy of the GNU General Public License version 0N/A * 2 along with this work; if not, write to the Free Software Foundation, 1472N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 1472N/A * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 0N/A * CA 95054 USA or visit www.sun.com if you need additional information or 0N/A * have any questions. 0N/A * A class containing static convenience methods for locating 0N/A * <code>ImageReader</code>s and <code>ImageWriter</code>s, and 0N/A * performing simple encoding and decoding. * Constructor is private to prevent instantiation. * Scans for plug-ins on the application class path, * loads their service provider classes, and registers a service * provider instance for each one found with the * <code>IIORegistry</code>. * <p>This method is needed because the application class path can * theoretically change, or additional plug-ins may become available. * Rather than re-scanning the classpath on every invocation of the * API, the class path is scanned automatically only on the first * invocation. Clients can call this method to prompt a re-scan. * Thus this method need only be invoked by sophisticated applications * which dynamically make new plug-ins available at runtime. * <p> The <code>getResources</code> method of the context * <code>ClassLoader</code> is used locate JAR files containing * where <i>classname</i> is one of <code>ImageReaderSpi</code>, * <code>ImageWriterSpi</code>, <code>ImageTranscoderSpi</code>, * <code>ImageInputStreamSpi</code>, or * <code>ImageOutputStreamSpi</code>, along the application class * <p> The contents of the located files indicate the names of * actual implementation classes which implement the * aforementioned service provider interfaces; the default class * loader is then used to load each of these classes and to * instantiate an instance of each class, which is then placed * into the registry for later retrieval. * <p> The exact set of locations searched depends on the * implementation of the Java runtime enviroment. * @see ClassLoader#getResources * A class to hold information about caching. Each * <code>ThreadGroup</code> will have its own copy * via the <code>AppContext</code> mechanism. * Returns the <code>CacheInfo</code> object associated with this * <code>ThreadGroup</code>. * Returns the default temporary (cache) directory as defined by the * java.io.tmpdir system property. * Determines whether the caller has write access to the cache * directory, stores the result in the <code>CacheInfo</code> object, * and returns the decision. This method helps to prevent mysterious * SecurityExceptions to be thrown when this convenience class is used * in an applet, for example. // we have to check whether we can read, write, // and delete cache files. // So, compose cache file path and check it. * Sets a flag indicating whether a disk-based cache file should * be used when creating <code>ImageInputStream</code>s and * <code>ImageOutputStream</code>s. * <p> When reading from a standard <code>InputStream</code>>, it * may be necessary to save previously read information in a cache * since the underlying stream does not allow data to be re-read. * Similarly, when writing to a standard * <code>OutputStream</code>, a cache may be used to allow a * previously written value to be changed before flushing it to * <p> The cache may reside in main memory or on disk. Setting * this flag to <code>false</code> disallows the use of disk for * future streams, which may be advantageous when working with * small images, as the overhead of creating and destroying files * <p> On startup, the value is set to <code>true</code>. * @param useCache a <code>boolean</code> indicating whether a * cache file should be used, in cases where it is optional. * Returns the current value set by <code>setUseCache</code>, or * <code>true</code> if no explicit setting has been made. * @return true if a disk-based cache may be used for * <code>ImageInputStream</code>s and * <code>ImageOutputStream</code>s. * Sets the directory where cache files are to be created. A * value of <code>null</code> indicates that the system-dependent * default temporary-file directory is to be used. If * <code>getUseCache</code> returns false, this value is ignored. * @param cacheDirectory a <code>File</code> specifying a directory. * @see File#createTempFile(String, String, File) * @exception SecurityException if the security manager denies * access to the directory. * @exception IllegalArgumentException if <code>cacheDir</code> is * non-<code>null</code> but is not a directory. * @see #getCacheDirectory * Returns the current value set by * <code>setCacheDirectory</code>, or <code>null</code> if no * explicit setting has been made. * @return a <code>File</code> indicating the directory where * cache files will be created, or <code>null</code> to indicate * the system-dependent default temporary-file directory. * @see #setCacheDirectory * Returns an <code>ImageInputStream</code> that will take its * input from the given <code>Object</code>. The set of * <code>ImageInputStreamSpi</code>s registered with the * <code>IIORegistry</code> class is queried and the first one * that is able to take input from the supplied object is used to * create the returned <code>ImageInputStream</code>. If no * suitable <code>ImageInputStreamSpi</code> exists, * <code>null</code> is returned. * <p> The current cache settings from <code>getUseCache</code>and * <code>getCacheDirectory</code> will be used to control caching. * @param input an <code>Object</code> to be used as an input * source, such as a <code>File</code>, readable * <code>RandomAccessFile</code>, or <code>InputStream</code>. * @return an <code>ImageInputStream</code>, or <code>null</code>. * @exception IllegalArgumentException if <code>input</code> * @exception IOException if a cache file is needed but cannot be * @see javax.imageio.spi.ImageInputStreamSpi // Ensure category is present * Returns an <code>ImageOutputStream</code> that will send its * output to the given <code>Object</code>. The set of * <code>ImageOutputStreamSpi</code>s registered with the * <code>IIORegistry</code> class is queried and the first one * that is able to send output from the supplied object is used to * create the returned <code>ImageOutputStream</code>. If no * suitable <code>ImageOutputStreamSpi</code> exists, * <code>null</code> is returned. * <p> The current cache settings from <code>getUseCache</code>and * <code>getCacheDirectory</code> will be used to control caching. * @param output an <code>Object</code> to be used as an output * destination, such as a <code>File</code>, writable * <code>RandomAccessFile</code>, or <code>OutputStream</code>. * @return an <code>ImageOutputStream</code>, or * @exception IllegalArgumentException if <code>output</code> is * @exception IOException if a cache file is needed but cannot be * @see javax.imageio.spi.ImageOutputStreamSpi // Ensure category is present // Ensure category is present * Returns an array of <code>String</code>s listing all of the * informal format names understood by the current set of registered * @return an array of <code>String</code>s. * Returns an array of <code>String</code>s listing all of the * MIME types understood by the current set of registered * @return an array of <code>String</code>s. * Returns an array of <code>String</code>s listing all of the * file suffixes associated with the formats understood * by the current set of registered readers. * @return an array of <code>String</code>s. // Contains ImageReaderSpis // Deregister the spi in this case, but only as // even though plug-ins are supposed to take // method returns an array of Strings * Returns an <code>Iterator</code> containing all currently * registered <code>ImageReader</code>s that claim to be able to * decode the supplied <code>Object</code>, typically an * <code>ImageInputStream</code>. * <p> The stream position is left at its prior position upon * @param input an <code>ImageInputStream</code> or other * <code>Object</code> containing encoded image data. * @return an <code>Iterator</code> containing <code>ImageReader</code>s. * @exception IllegalArgumentException if <code>input</code> is * @see javax.imageio.spi.ImageReaderSpi#canDecodeInput // Ensure category is present * Returns an <code>Iterator</code> containing all currently * registered <code>ImageReader</code>s that claim to be able to * decode the named format. * @param formatName a <code>String</code> containing the informal * name of a format (<i>e.g.</i>, "jpeg" or "tiff". * @return an <code>Iterator</code> containing * <code>ImageReader</code>s. * @exception IllegalArgumentException if <code>formatName</code> * @see javax.imageio.spi.ImageReaderSpi#getFormatNames // Ensure category is present * Returns an <code>Iterator</code> containing all currently * registered <code>ImageReader</code>s that claim to be able to * decode files with the given suffix. * @param fileSuffix a <code>String</code> containing a file * suffix (<i>e.g.</i>, "jpg" or "tiff"). * @return an <code>Iterator</code> containing * <code>ImageReader</code>s. * @exception IllegalArgumentException if <code>fileSuffix</code> * @see javax.imageio.spi.ImageReaderSpi#getFileSuffixes // Ensure category is present * Returns an <code>Iterator</code> containing all currently * registered <code>ImageReader</code>s that claim to be able to * decode files with the given MIME type. * @param MIMEType a <code>String</code> containing a file * @return an <code>Iterator</code> containing * <code>ImageReader</code>s. * @exception IllegalArgumentException if <code>MIMEType</code> is * @see javax.imageio.spi.ImageReaderSpi#getMIMETypes // Ensure category is present * Returns an array of <code>String</code>s listing all of the * informal format names understood by the current set of registered * @return an array of <code>String</code>s. * Returns an array of <code>String</code>s listing all of the * MIME types understood by the current set of registered * @return an array of <code>String</code>s. * Returns an array of <code>String</code>s listing all of the * file suffixes associated with the formats understood * by the current set of registered writers. * @return an array of <code>String</code>s. // Contains ImageWriterSpis // Deregister the spi in this case, but only as a writerSpi * Returns an <code>Iterator</code> containing all currently * registered <code>ImageWriter</code>s that claim to be able to * encode the named format. * @param formatName a <code>String</code> containing the informal * name of a format (<i>e.g.</i>, "jpeg" or "tiff". * @return an <code>Iterator</code> containing * <code>ImageWriter</code>s. * @exception IllegalArgumentException if <code>formatName</code> is * @see javax.imageio.spi.ImageWriterSpi#getFormatNames // Ensure category is present * Returns an <code>Iterator</code> containing all currently * registered <code>ImageWriter</code>s that claim to be able to * encode files with the given suffix. * @param fileSuffix a <code>String</code> containing a file * suffix (<i>e.g.</i>, "jpg" or "tiff"). * @return an <code>Iterator</code> containing <code>ImageWriter</code>s. * @exception IllegalArgumentException if <code>fileSuffix</code> is * @see javax.imageio.spi.ImageWriterSpi#getFileSuffixes // Ensure category is present * Returns an <code>Iterator</code> containing all currently * registered <code>ImageWriter</code>s that claim to be able to * encode files with the given MIME type. * @param MIMEType a <code>String</code> containing a file * @return an <code>Iterator</code> containing <code>ImageWriter</code>s. * @exception IllegalArgumentException if <code>MIMEType</code> is * @see javax.imageio.spi.ImageWriterSpi#getMIMETypes // Ensure category is present * Returns an <code>ImageWriter</code>corresponding to the given * <code>ImageReader</code>, if there is one, or <code>null</code> * if the plug-in for this <code>ImageReader</code> does not * specify a corresponding <code>ImageWriter</code>, or if the * given <code>ImageReader</code> is not registered. This * mechanism may be used to obtain an <code>ImageWriter</code> * that will understand the internal structure of non-pixel * metadata (as encoded by <code>IIOMetadata</code> objects) * generated by the <code>ImageReader</code>. By obtaining this * data from the <code>ImageReader</code> and passing it on to the * <code>ImageWriter</code> obtained with this method, a client * program can read an image, modify it in some way, and write it * back out preserving all metadata, without having to understand * anything about the structure of the metadata, or even about * the image format. Note that this method returns the * "preferred" writer, which is the first in the list returned by * <code>javax.imageio.spi.ImageReaderSpi.getImageWriterSpiNames()</code>. * @param reader an instance of a registered <code>ImageReader</code>. * @return an <code>ImageWriter</code>, or null. * @exception IllegalArgumentException if <code>reader</code> is * @see #getImageReader(ImageWriter) * @see javax.imageio.spi.ImageReaderSpi#getImageWriterSpiNames() // Ensure category is present // Deregister the spi in this case, but only as a writerSpi * Returns an <code>ImageReader</code>corresponding to the given * <code>ImageWriter</code>, if there is one, or <code>null</code> * if the plug-in for this <code>ImageWriter</code> does not * specify a corresponding <code>ImageReader</code>, or if the * given <code>ImageWriter</code> is not registered. This method * is provided principally for symmetry with * <code>getImageWriter(ImageReader)</code>. Note that this * method returns the "preferred" reader, which is the first in * javax.imageio.spi.ImageWriterSpi.<code>getImageReaderSpiNames()</code>. * @param writer an instance of a registered <code>ImageWriter</code>. * @return an <code>ImageReader</code>, or null. * @exception IllegalArgumentException if <code>writer</code> is * @see #getImageWriter(ImageReader) * @see javax.imageio.spi.ImageWriterSpi#getImageReaderSpiNames() // Ensure category is present // Deregister the spi in this case, but only as a readerSpi * Returns an <code>Iterator</code> containing all currently * registered <code>ImageWriter</code>s that claim to be able to * encode images of the given layout (specified using an * <code>ImageTypeSpecifier</code>) in the given format. * @param type an <code>ImageTypeSpecifier</code> indicating the * layout of the image to be written. * @param formatName the informal name of the <code>format</code>. * @return an <code>Iterator</code> containing <code>ImageWriter</code>s. * @exception IllegalArgumentException if any parameter is * @see javax.imageio.spi.ImageWriterSpi#canEncodeImage(ImageTypeSpecifier) // Ensure category is present // Contains ImageTranscoderSpis * Returns an <code>Iterator</code> containing all currently * registered <code>ImageTranscoder</code>s that claim to be * able to transcode between the metadata of the given * <code>ImageReader</code> and <code>ImageWriter</code>. * @param reader an <code>ImageReader</code>. * @param writer an <code>ImageWriter</code>. * @return an <code>Iterator</code> containing * <code>ImageTranscoder</code>s. * @exception IllegalArgumentException if <code>reader</code> or * <code>writer</code> is <code>null</code>. // Ensure category is present * Returns a <code>BufferedImage</code> as the result of decoding * a supplied <code>File</code> with an <code>ImageReader</code> * chosen automatically from among those currently registered. * The <code>File</code> is wrapped in an * <code>ImageInputStream</code>. If no registered * <code>ImageReader</code> claims to be able to read the * resulting stream, <code>null</code> is returned. * <p> The current cache settings from <code>getUseCache</code>and * <code>getCacheDirectory</code> will be used to control caching in the * <code>ImageInputStream</code> that is created. * <p> Note that there is no <code>read</code> method that takes a * filename as a <code>String</code>; use this method instead after * creating a <code>File</code> from the filename. * <p> This method does not attempt to locate * <code>ImageReader</code>s that can read directly from a * <code>File</code>; that may be accomplished using * <code>IIORegistry</code> and <code>ImageReaderSpi</code>. * @param input a <code>File</code> to read from. * @return a <code>BufferedImage</code> containing the decoded * contents of the input, or <code>null</code>. * @exception IllegalArgumentException if <code>input</code> is * @exception IOException if an error occurs during reading. throw new IIOException(
"Can't create an ImageInputStream!");
* Returns a <code>BufferedImage</code> as the result of decoding * a supplied <code>InputStream</code> with an <code>ImageReader</code> * chosen automatically from among those currently registered. * The <code>InputStream</code> is wrapped in an * <code>ImageInputStream</code>. If no registered * <code>ImageReader</code> claims to be able to read the * resulting stream, <code>null</code> is returned. * <p> The current cache settings from <code>getUseCache</code>and * <code>getCacheDirectory</code> will be used to control caching in the * <code>ImageInputStream</code> that is created. * <p> This method does not attempt to locate * <code>ImageReader</code>s that can read directly from an * <code>InputStream</code>; that may be accomplished using * <code>IIORegistry</code> and <code>ImageReaderSpi</code>. * <p> This method <em>does not</em> close the provided * <code>InputStream</code> after the read operation has completed; * it is the responsibility of the caller to close the stream, if desired. * @param input an <code>InputStream</code> to read from. * @return a <code>BufferedImage</code> containing the decoded * contents of the input, or <code>null</code>. * @exception IllegalArgumentException if <code>input</code> is * @exception IOException if an error occurs during reading. * Returns a <code>BufferedImage</code> as the result of decoding * a supplied <code>URL</code> with an <code>ImageReader</code> * chosen automatically from among those currently registered. An * <code>InputStream</code> is obtained from the <code>URL</code>, * which is wrapped in an <code>ImageInputStream</code>. If no * registered <code>ImageReader</code> claims to be able to read * the resulting stream, <code>null</code> is returned. * <p> The current cache settings from <code>getUseCache</code>and * <code>getCacheDirectory</code> will be used to control caching in the * <code>ImageInputStream</code> that is created. * <p> This method does not attempt to locate * <code>ImageReader</code>s that can read directly from a * <code>URL</code>; that may be accomplished using * <code>IIORegistry</code> and <code>ImageReaderSpi</code>. * @param input a <code>URL</code> to read from. * @return a <code>BufferedImage</code> containing the decoded * contents of the input, or <code>null</code>. * @exception IllegalArgumentException if <code>input</code> is * @exception IOException if an error occurs during reading. throw new IIOException(
"Can't get input stream from URL!", e);
* Returns a <code>BufferedImage</code> as the result of decoding * a supplied <code>ImageInputStream</code> with an * <code>ImageReader</code> chosen automatically from among those * currently registered. If no registered * <code>ImageReader</code> claims to be able to read the stream, * <code>null</code> is returned. * <p> Unlike most other methods in this class, this method <em>does</em> * close the provided <code>ImageInputStream</code> after the read * operation has completed, unless <code>null</code> is returned, * in which case this method <em>does not</em> close the stream. * @param stream an <code>ImageInputStream</code> to read from. * @return a <code>BufferedImage</code> containing the decoded * contents of the input, or <code>null</code>. * @exception IllegalArgumentException if <code>stream</code> is * @exception IOException if an error occurs during reading. * Writes an image using the an arbitrary <code>ImageWriter</code> * that supports the given format to an * <code>ImageOutputStream</code>. The image is written to the * <code>ImageOutputStream</code> starting at the current stream * pointer, overwriting existing stream data from that point * <p> This method <em>does not</em> close the provided * <code>ImageOutputStream</code> after the write operation has completed; * it is the responsibility of the caller to close the stream, if desired. * @param im a <code>RenderedImage</code> to be written. * @param formatName a <code>String</code> containg the informal * @param output an <code>ImageOutputStream</code> to be written to. * @return <code>false</code> if no appropriate writer is found. * @exception IllegalArgumentException if any parameter is * @exception IOException if an error occurs during writing. * Writes an image using an arbitrary <code>ImageWriter</code> * that supports the given format to a <code>File</code>. If * there is already a <code>File</code> present, its contents are * @param im a <code>RenderedImage</code> to be written. * @param formatName a <code>String</code> containg the informal * @param output a <code>File</code> to be written to. * @return <code>false</code> if no appropriate writer is found. * @exception IllegalArgumentException if any parameter is * @exception IOException if an error occurs during writing. /* Do not make changes in the file system if we have * Writes an image using an arbitrary <code>ImageWriter</code> * that supports the given format to an <code>OutputStream</code>. * <p> This method <em>does not</em> close the provided * <code>OutputStream</code> after the write operation has completed; * it is the responsibility of the caller to close the stream, if desired. * <p> The current cache settings from <code>getUseCache</code>and * <code>getCacheDirectory</code> will be used to control caching. * @param im a <code>RenderedImage</code> to be written. * @param formatName a <code>String</code> containg the informal * @param output an <code>OutputStream</code> to be written to. * @return <code>false</code> if no appropriate writer is found. * @exception IllegalArgumentException if any parameter is * @exception IOException if an error occurs during writing. * Returns <code>ImageWriter</code> instance according to given * rendered image and image format or <code>null</code> if there * is no appropriate writer. * Writes image to output stream using given image writer.