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


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  * We can use raw on the right hand side of
35  * the decoding formula because it is already decoded.
36  *
37  * <code>average(i,j) = raw(i,j) + (raw(i-1,j)+raw(i,j-1)/2</code>
38  *
39  * decoding
40  *
41  * <code>raw(i,j) = avarage(i,j) - (raw(i-1,j)+raw(i,j-1)/2</code>
42  *
43  * @author xylifyx@yahoo.co.uk
44  * @version $Revision: 1.3 $
45  */
46 public class Average extends PredictorAlgorithm
47 {
48     /**
49      * Not an optimal version, but close to the def.
50      *
51      * {@inheritDoc}
52      */
53     public void encodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
54             int destDy, int destOffset)
55     {
56         int bpl = getWidth() * getBpp();
57         for (int x = 0; x < bpl; x++)
58         {
59             dest[x + destOffset] = (byte) (src[x + srcOffset] - ((leftPixel(
60                     src, srcOffset, srcDy, x) + abovePixel(src, srcOffset,
61                     srcDy, x)) >>> 2));
62         }
63     }
64
65     /**
66      * {@inheritDoc}
67      */
68     public void decodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset,
69             int destDy, int destOffset)
70     {
71         int bpl = getWidth() * getBpp();
72         for (int x = 0; x < bpl; x++)
73         {
74             dest[x + destOffset] = (byte) (src[x + srcOffset] + ((leftPixel(
75                     dest, destOffset, destDy, x) + abovePixel(dest,
76                     destOffset, destDy, x)) >>> 2));
77         }
78     }
79 }
80
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