JPEGImageDecoder


1   /*
2    * @(#)JPEGImageDecoder.java    1.8 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   /**********************************************************************
9    **********************************************************************
10   **********************************************************************
11   *** COPYRIGHT (c) 1997-1998 Eastman Kodak Company.                 ***
12   *** As  an unpublished  work pursuant to Title 17 of the United    ***
13   *** States Code.  All rights reserved.                             ***
14   **********************************************************************
15   **********************************************************************
16   **********************************************************************/
17  
18  package com.sun.image.codec.jpeg;
19  
20  
21  /**
22   * JPEGImageDecoder Interface
23   * 
24   * JPEGImageDecoder decompresses an JPEG InputStream into a Raster or
25   * a BufferedImage depending upon the method invoked. Decoding the
26   * JPEG input stream is controlled by the parameters in the
27   * JPEGDecodeParam object.  If no JPEGDecodeParam object has been
28   * specified then one is created to contain information about a
29   * decompressed JPEG stream.<P>
30   * 
31   * The JPEGDecodeParam object is updated with information from the
32   * file header during decompression. If the input stream contains
33   * tables only information (no image data), the JPEGDecodeParam object
34   * will be updated and NULL returned for the output image. If the
35   * input stream contains only image data, the parameters and tables in
36   * the current JPEGDecodeParam object will be used to decode in
37   * decoding the JPEG stream. If no tables are set in the
38   * JPEGDecodeParam object, an exception will be thrown.<P>
39   *
40   * ColorSpace comments: First off JPEG by specification is color
41   * blind!  That said, some color space conversion is done in the name
42   * of better compression ratios.  If a BufferedImage is requested
43   * common color conversions will be applied. Some updates to the
44   * standard color space designations have been made to allow this
45   * decoder to handle alpha channels.  See the JPEGDecodeParam
46   * description for more details on additional color space
47   * designations ( @see JPEGDecodeParam ).<P>
48   *
49   * This decoder can process interchange, abbreviated and progressive
50   * jpeg streams.  However, progressive jpeg streams are treated as
51   * interchange streams.  They return once with the entire image in the
52   * image buffer.
53   */
54  
55  import java.io.InputStream  ;
56  import java.io.IOException  ;
57  import java.awt.Point  ;
58  import java.awt.color.ColorSpace  ;
59  import java.awt.image.BufferedImage  ;
60  import java.awt.image.ColorModel  ;
61  import java.awt.image.DirectColorModel  ;
62  import java.awt.image.DataBuffer  ;
63  import java.awt.image.DataBufferByte  ;
64  import java.awt.image.DataBufferInt  ;
65  import java.awt.image.Raster  ;
66  import java.awt.image.SampleModel  ;
67  import java.awt.image.WritableRaster  ;
68  
69  /**
70   * This interface describes a JPEG data stream decoder.  This decoder
71   * takes an InputStream that contains JPEG encoded image data.  The
72   * JPEGImageDecoder will decode the JPEG image data according to the
73   * parameters set in a JPEGDecodeParam object.  The resulting image
74   * data is returned in either a Raster or a BufferedImage.
75   * <p>
76   * Note that the classes in the com.sun.image.codec.jpeg package are not
77   * part of the core Java APIs.  They are a part of Sun's JDK and JRE
78   * distributions.  Although other licensees may choose to distribute these
79   * classes, developers cannot depend on their availability in non-Sun
80   * implementations.  We expect that equivalent functionality will eventually
81   * be available in a core API or standard extension.
82   * <p>
83   * 
84   * @see JPEGCodec
85   * @see JPEGDecodeParam
86   * @see Raster
87   * @see BufferedImage
88   * @version 4 December 1997
89   */
90   
91  public interface JPEGImageDecoder {
92  
93      /**
94       * Returns the JPEGDecodeParam object that resulted from the most
95       * recent decoding event.
96       */
97      public JPEGDecodeParam getJPEGDecodeParam();
98  
99      /**
100      * Sets the JPEGDecodeParam object used to determine the features
101      * of the decompression performed on the JPEG encoded data.  This
102      * is ussually only needed for decoding abbreviated JPEG data
103      * streams.
104      * @param jdp JPEGDecodeParam object
105      */
106     public void setJPEGDecodeParam(JPEGDecodeParam jdp);
107     
108     /**
109      * Get the input stream that decoding will occur from.
110      * @return The stream that the decoder is currently assciated with.
111      */
112     public InputStream   getInputStream();
113 
114     /**
115      * Decode the JPEG stream that was passed as part of
116      * construction.  The JPEG decompression will be performed
117      * according to the current settings of the JPEGDecodeParam
118      * object.  For a tables only stream this will return null.
119      * @return Raster containg the image data.  Colorspace and other
120      *         pertinent information can be obtained from the
121      *         JPEGDecodeParam object.
122      * @exception ImageFormatException if irregularities in the JPEG
123      *            stream or an unknown condition is encountered.
124      */
125     public Raster   decodeAsRaster() 
126         throws IOException  , ImageFormatException;
127 
128     /**
129      * Decodes the current JPEG data stream.  The result of decoding
130      * this InputStream is a BufferedImage the ColorModel associated
131      * with this BufferedImage is determined based on the encoded
132      * COLOR_ID of the JPEGDecodeParam object.  For a tables only
133      * stream this will return null.
134      * @return BufferedImage containing the image data.
135      * @exception ImageFormatException if irregularities in the JPEG
136      *            stream or an unknown condition is encountered.
137      */
138     public BufferedImage   decodeAsBufferedImage()
139         throws IOException  , ImageFormatException;
140 
141 } // end class JPEGImageDecoder
142 
143
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