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context.cpp
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1 /* -*-C-*-
2 ********************************************************************************
3 *
4 * File: context.c (Formerly context.c)
5 * Description: Context checking functions
6 * Author: Mark Seaman, OCR Technology
7 * Created: Thu Feb 15 11:18:24 1990
8 * Modified: Tue Jul 9 17:38:16 1991 (Mark Seaman) marks@hpgrlt
9 * Language: C
10 * Package: N/A
11 * Status: Experimental (Do Not Distribute)
12 *
13 * (c) Copyright 1990, Hewlett-Packard Company.
14 ** Licensed under the Apache License, Version 2.0 (the "License");
15 ** you may not use this file except in compliance with the License.
16 ** You may obtain a copy of the License at
17 ** http://www.apache.org/licenses/LICENSE-2.0
18 ** Unless required by applicable law or agreed to in writing, software
19 ** distributed under the License is distributed on an "AS IS" BASIS,
20 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
21 ** See the License for the specific language governing permissions and
22 ** limitations under the License.
23 *
24 *********************************************************************************/
25
26 #include "dict.h"
27 #include "tprintf.h"
28 #include "unicharset.h"
29
30 namespace tesseract {
31
32 static const int kMinAbsoluteGarbageWordLength = 10;
33 static const float kMinAbsoluteGarbageAlphanumFrac = 0.5f;
34
35 const int case_state_table[6][4] = { {
36 /* 0. Begining of word */
37 /* P U L D */
38 /* -1. Error on case */
39 0, 1, 5, 4
40 },
41 { /* 1. After initial capital */
42 0, 3, 2, 4
43 },
44 { /* 2. After lower case */
45 0, -1, 2, -1
46 },
47 { /* 3. After upper case */
48 0, 3, -1, 4
49 },
50 { /* 4. After a digit */
51 0, -1, -1, 4
52 },
53 { /* 5. After initial lower case */
54 5, -1, 2, -1
55 },
56 };
57
58 int Dict::case_ok(const WERD_CHOICE &word, const UNICHARSET &unicharset) {
59 int last_state = 0;
60 int state = 0;
61 int x;
62 for (x = 0; x < word.length(); ++x) {
63 UNICHAR_ID ch_id = word.unichar_id(x);
64 if (unicharset.get_isupper(ch_id))
65 state = case_state_table[state][1];
66 else if (unicharset.get_islower(ch_id))
67 state = case_state_table[state][2];
68 else if (unicharset.get_isdigit(ch_id))
69 state = case_state_table[state][3];
70 else
71 state = case_state_table[state][0];
72 if (state == -1) return false;
73 last_state = state;
74 }
75 return state != 5; // single lower is bad
76 }
77
78 bool Dict::absolute_garbage(const WERD_CHOICE &word,
79 const UNICHARSET &unicharset) {
80 if (word.length() < kMinAbsoluteGarbageWordLength) return false;
81 int num_alphanum = 0;
82 for (int x = 0; x < word.length(); ++x) {
83 num_alphanum += (unicharset.get_isalpha(word.unichar_id(x)) ||
84 unicharset.get_isdigit(word.unichar_id(x)));
85 }
86 return (static_cast<float>(num_alphanum) /
87 static_cast<float>(word.length()) < kMinAbsoluteGarbageAlphanumFrac);
88 }
89
90 } // namespace tesseract