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 <span id="projectnumber">3.03</span>
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<div class="title">/usr/local/google/home/jbreiden/tesseract-ocr-read-only/ccutil/qrsequence.h</div> </div>
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<div class="contents">
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<a href="a00846.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001
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<a name="l00002"></a>00002 <span class="comment">// File: qrsequence.h</span>
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<a name="l00003"></a>00003 <span class="comment">// Description: Quasi-random sequence generator class.</span>
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<a name="l00004"></a>00004 <span class="comment">// Author: Ranjith Unnikrishnan</span>
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<a name="l00005"></a>00005 <span class="comment">// Created: Wed May 20 2009</span>
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<a name="l00006"></a>00006 <span class="comment">//</span>
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<a name="l00007"></a>00007 <span class="comment">// Class to generate a (deterministic) quasi-random Van der Corput sequence that</span>
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<a name="l00008"></a>00008 <span class="comment">// covers the interval [0,N) without repetition.</span>
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<a name="l00009"></a>00009 <span class="comment">//</span>
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<a name="l00010"></a>00010 <span class="comment">// The sequence is generated by reversing the base-2 representation of the</span>
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<a name="l00011"></a>00011 <span class="comment">// sequence of natural numbers {0, 1,... M-1}, where M is 2^{num_bits_} and</span>
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<a name="l00012"></a>00012 <span class="comment">// num_bits is the minimum number of bits required to represent N. If a reversed</span>
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<a name="l00013"></a>00013 <span class="comment">// numbers is >= N it is rejected and the next natural number is considered</span>
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<a name="l00014"></a>00014 <span class="comment">// until a valid output number is found.</span>
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<a name="l00015"></a>00015 <span class="comment">//</span>
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<a name="l00016"></a>00016 <span class="comment">// (C) Copyright 2009, Google Inc.</span>
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<a name="l00017"></a>00017 <span class="comment">// Licensed under the Apache License, Version 2.0 (the "License"); you may not</span>
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<a name="l00018"></a>00018 <span class="comment">// use this file except in compliance with the License. You may obtain a copy</span>
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<a name="l00019"></a>00019 <span class="comment">// of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required</span>
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<a name="l00020"></a>00020 <span class="comment">// by applicable law or agreed to in writing, software distributed under the</span>
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<a name="l00021"></a>00021 <span class="comment">// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS</span>
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<a name="l00022"></a>00022 <span class="comment">// OF ANY KIND, either express or implied. See the License for the specific</span>
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<a name="l00023"></a>00023 <span class="comment">// language governing permissions and limitations under the License.</span>
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<a name="l00024"></a>00024 <span class="comment">//</span>
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<a name="l00026"></a>00026 <span class="comment"></span>
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<a name="l00027"></a>00027 <span class="preprocessor">#ifndef TESSERACT_CCUTIL_QRSEQUENCE_H_</span>
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<a name="l00028"></a>00028 <span class="preprocessor"></span><span class="preprocessor">#define TESSERACT_CCUTIL_QRSEQUENCE_H_</span>
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<a name="l00029"></a>00029 <span class="preprocessor"></span>
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<a name="l00030"></a>00030 <span class="preprocessor">#include <math.h></span>
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<a name="l00031"></a>00031
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<a name="l00032"></a><a class="code" href="a00512.html">00032</a> <span class="keyword">class </span><a class="code" href="a00512.html">QRSequenceGenerator</a> {
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<a name="l00033"></a>00033 <span class="keyword">public</span>:
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<a name="l00034"></a>00034 <span class="comment">// Object is initalized with the size of the output range.</span>
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<a name="l00035"></a><a class="code" href="a00512.html#a5a059ef6ea8b396ad0569e7e948609f8">00035</a> <span class="keyword">explicit</span> <a class="code" href="a00512.html#a5a059ef6ea8b396ad0569e7e948609f8">QRSequenceGenerator</a>(<span class="keywordtype">int</span> N) : <a class="code" href="a00512.html#a7c5369f6274a766bd8fa27c73def6821">N_</a>(N), <a class="code" href="a00512.html#ab764a4da80a6383e730def95256987e7">next_num_</a>(0) {
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<a name="l00036"></a>00036 <a class="code" href="a00512.html#abc925af9d97d630cd000a20c719c8c60">num_bits_</a> = <span class="keyword">static_cast<</span><span class="keywordtype">int</span><span class="keyword">></span>(ceil(log(static_cast<double>(N)) / log(2.0)));
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<a name="l00037"></a>00037 }
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<a name="l00038"></a>00038
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<a name="l00039"></a>00039 <span class="comment">// Main worker method that retrieves the next number in the sequence.</span>
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<a name="l00040"></a>00040 <span class="comment">// Returns kInvalidVal if called more than N times after object initialization</span>
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<a name="l00041"></a><a class="code" href="a00512.html#a28c125707aded762182e647e0ec91900">00041</a> <span class="keywordtype">int</span> <a class="code" href="a00512.html#a28c125707aded762182e647e0ec91900">GetVal</a>() {
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<a name="l00042"></a>00042 <span class="keyword">const</span> <span class="keywordtype">int</span> kInvalidVal = -1;
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<a name="l00043"></a>00043 <span class="keyword">const</span> <span class="keywordtype">int</span> kMaxNaturalNumberValue = 1 << <a class="code" href="a00512.html#abc925af9d97d630cd000a20c719c8c60">num_bits_</a>;
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<a name="l00044"></a>00044 <span class="keywordflow">if</span> (<a class="code" href="a00512.html#ab764a4da80a6383e730def95256987e7">next_num_</a> >= kMaxNaturalNumberValue)
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<a name="l00045"></a>00045 <span class="keywordflow">return</span> kInvalidVal;
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<a name="l00046"></a>00046 <span class="keywordtype">int</span> n = <a class="code" href="a00512.html#ab764a4da80a6383e730def95256987e7">next_num_</a>;
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<a name="l00047"></a>00047
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<a name="l00048"></a>00048 <span class="keywordflow">while</span> (<a class="code" href="a00512.html#ab764a4da80a6383e730def95256987e7">next_num_</a> < kMaxNaturalNumberValue) {
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<a name="l00049"></a>00049 n = <a class="code" href="a00512.html#a76df4c96183f70454be79371ad16ba62">GetBinaryReversedInteger</a>(<a class="code" href="a00512.html#ab764a4da80a6383e730def95256987e7">next_num_</a>++);
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<a name="l00050"></a>00050 <span class="keywordflow">if</span> (n < <a class="code" href="a00512.html#a7c5369f6274a766bd8fa27c73def6821">N_</a>) <span class="keywordflow">break</span>;
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<a name="l00051"></a>00051 }
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<a name="l00052"></a>00052 <span class="keywordflow">return</span> (<a class="code" href="a00512.html#ab764a4da80a6383e730def95256987e7">next_num_</a> > kMaxNaturalNumberValue) ? kInvalidVal : n;
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<a name="l00053"></a>00053 }
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<a name="l00054"></a>00054
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<a name="l00055"></a>00055 <span class="keyword">protected</span>:
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<a name="l00056"></a>00056 <span class="comment">// Outputs the integer formed by reversing the bits of the input integer. Only</span>
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<a name="l00057"></a>00057 <span class="comment">// the lowest num_bits_ bits of the input integer are reversed.</span>
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<a name="l00058"></a><a class="code" href="a00512.html#a76df4c96183f70454be79371ad16ba62">00058</a> <span class="keywordtype">int</span> <a class="code" href="a00512.html#a76df4c96183f70454be79371ad16ba62">GetBinaryReversedInteger</a>(<span class="keywordtype">int</span> in_val)<span class="keyword"> const </span>{
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<a name="l00059"></a>00059 <span class="keywordtype">int</span> bit_pos = <a class="code" href="a00512.html#abc925af9d97d630cd000a20c719c8c60">num_bits_</a>;
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<a name="l00060"></a>00060 <span class="keywordtype">int</span> out_val = 0;
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<a name="l00061"></a>00061 <span class="keywordflow">while</span>(bit_pos--) {
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<a name="l00062"></a>00062 <span class="comment">// Set the value of the last bit.</span>
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<a name="l00063"></a>00063 out_val |= (in_val & 0x1);
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<a name="l00064"></a>00064 <span class="keywordflow">if</span> (bit_pos > 0) {
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<a name="l00065"></a>00065 <span class="comment">// Left-shift output value to prepare for storing the next bit.</span>
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<a name="l00066"></a>00066 out_val <<= 1;
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<a name="l00067"></a>00067 }
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<a name="l00068"></a>00068 <span class="comment">// Right-shift input value to prepare for retrieving the next bit.</span>
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<a name="l00069"></a>00069 in_val >>= 1;
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<a name="l00070"></a>00070 }
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<a name="l00071"></a>00071 <span class="keywordflow">return</span> out_val;
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<a name="l00072"></a>00072 }
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<a name="l00073"></a><a class="code" href="a00512.html#a7c5369f6274a766bd8fa27c73def6821">00073</a> <span class="keywordtype">int</span> <a class="code" href="a00512.html#a7c5369f6274a766bd8fa27c73def6821">N_</a>;
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<a name="l00074"></a>00074 <span class="comment">// Next number to be considered for reversal and output.</span>
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<a name="l00075"></a><a class="code" href="a00512.html#ab764a4da80a6383e730def95256987e7">00075</a> <span class="keywordtype">int</span> <a class="code" href="a00512.html#ab764a4da80a6383e730def95256987e7">next_num_</a>;
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<a name="l00076"></a>00076 <span class="comment">// number of bits required to represent the numbers of the sequence</span>
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<a name="l00077"></a><a class="code" href="a00512.html#abc925af9d97d630cd000a20c719c8c60">00077</a> <span class="keywordtype">int</span> <a class="code" href="a00512.html#abc925af9d97d630cd000a20c719c8c60">num_bits_</a>;
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<a name="l00078"></a>00078 };
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<a name="l00079"></a>00079
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<a name="l00080"></a>00080 <span class="preprocessor">#endif // TESSERACT_CCUTIL_QRSEQUENCE_H_</span>
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<li class="navelem"><a class="el" href="a00846.html">qrsequence.h</a> </li>
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