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Java > Open Source Codes > org > pdfbox > pdmodel > graphics > predictor > Sub


1 /**
2  * Copyright (c) 2005, www.pdfbox.org
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright notice,
9  * this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright notice,
11  * this list of conditions and the following disclaimer in the documentation
12  * and/or other materials provided with the distribution.
13  * 3. Neither the name of pdfbox; nor the names of its
14  * contributors may be used to endorse or promote products derived from this
15  * software without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
18  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20  * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
24  * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
26  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27  *
28  * http://www.pdfbox.org
29  *
30  */
31 package org.pdfbox.pdmodel.graphics.predictor;
32
33 /**
34  * The sub algorithm.
35  *
36  * <code>Sub(i,j) = Raw(i,j) - Raw(i-1,j)</code>
37  *
38  * <code>Raw(i,j) = Sub(i,j) + Raw(i-1,j)</code>
39  *
40  * @author xylifyx@yahoo.co.uk
41  * @version $Revision: 1.3 $
42  */
43 public class Sub extends PredictorAlgorithm
44 {
45     /**
46      * {@inheritDoc}
47      */
48     public void encodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
49             int destDy, int destOffset)
50     {
51         int bpl = getWidth()*getBpp();
52         int bpp = getBpp();
53         // case: x < bpp
54 for (int x = 0; x < bpl && x < bpp; x++)
55         {
56             dest[x + destOffset] = src[x + srcOffset];
57         }
58         // otherwise
59 for (int x = getBpp(); x < bpl; x++)
60         {
61             dest[x + destOffset] = (byte) (src[x + srcOffset] - src[x
62                     + srcOffset - bpp]);
63         }
64     }
65
66     /**
67      * {@inheritDoc}
68      */
69     public void decodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
70             int destDy, int destOffset)
71     {
72         int bpl = getWidth()*getBpp();
73         int bpp = getBpp();
74         // case: x < bpp
75 for (int x = 0; x < bpl && x < bpp; x++)
76         {
77             dest[x + destOffset] = src[x + srcOffset];
78         }
79         // otherwise
80 for (int x = getBpp(); x < bpl; x++)
81         {
82             dest[x + destOffset] = (byte) (src[x + srcOffset] + dest[x
83                     + destOffset - bpp]);
84         }
85     }
86 }
87
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