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comparison mupdf-source/thirdparty/tesseract/src/ccstruct/dppoint.h @ 2:b50eed0cc0ef upstream

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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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1 /**********************************************************************
2 * File: dppoint.h
3 * Description: Simple generic dynamic programming class.
4 * Author: Ray Smith
5 * Created: Wed Mar 25 18:57:01 PDT 2009
6 *
7 * (C) Copyright 2009, Google Inc.
8 ** Licensed under the Apache License, Version 2.0 (the "License");
9 ** you may not use this file except in compliance with the License.
10 ** You may obtain a copy of the License at
11 ** http://www.apache.org/licenses/LICENSE-2.0
12 ** Unless required by applicable law or agreed to in writing, software
13 ** distributed under the License is distributed on an "AS IS" BASIS,
14 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 ** See the License for the specific language governing permissions and
16 ** limitations under the License.
17 *
18 **********************************************************************/
19
20 #ifndef TESSERACT_CCSTRUCT_DPPOINT_H_
21 #define TESSERACT_CCSTRUCT_DPPOINT_H_
22
23 #include <cstdint>
24
25 namespace tesseract {
26
27 // A simple class to provide a dynamic programming solution to a class of
28 // 1st-order problems in which the cost is dependent only on the current
29 // step and the best cost to that step, with a possible special case
30 // of using the variance of the steps, and only the top choice is required.
31 // Useful for problems such as finding the optimal cut points in a fixed-pitch
32 // (vertical or horizontal) situation.
33 // Skeletal Example:
34 // DPPoint* array = new DPPoint[width];
35 // for (int i = 0; i < width; i++) {
36 // array[i].AddLocalCost(cost_at_i)
37 // }
38 // DPPoint* best_end = DPPoint::Solve(..., array);
39 // while (best_end != nullptr) {
40 // int cut_index = best_end - array;
41 // best_end = best_end->best_prev();
42 // }
43 // delete [] array;
44 class DPPoint {
45 public:
46 // The cost function evaluates the total cost at this (excluding this's
47 // local_cost) and if it beats this's total_cost, then
48 // replace the appropriate values in this.
49 using CostFunc = int64_t (DPPoint::*)(const DPPoint *);
50
51 DPPoint()
52 : local_cost_(0)
53 , total_cost_(INT32_MAX)
54 , total_steps_(1)
55 , best_prev_(nullptr)
56 , n_(0)
57 , sig_x_(0)
58 , sig_xsq_(0) {}
59
60 // Solve the dynamic programming problem for the given array of points, with
61 // the given size and cost function.
62 // Steps backwards are limited to being between min_step and max_step
63 // inclusive.
64 // The return value is the tail of the best path.
65 static DPPoint *Solve(int min_step, int max_step, bool debug, CostFunc cost_func, int size,
66 DPPoint *points);
67
68 // A CostFunc that takes the variance of step into account in the cost.
69 int64_t CostWithVariance(const DPPoint *prev);
70
71 // Accessors.
72 int total_cost() const {
73 return total_cost_;
74 }
75 int Pathlength() const {
76 return total_steps_;
77 }
78 const DPPoint *best_prev() const {
79 return best_prev_;
80 }
81 void AddLocalCost(int new_cost) {
82 local_cost_ += new_cost;
83 }
84
85 private:
86 // Code common to different cost functions.
87
88 // Update the other members if the cost is lower.
89 void UpdateIfBetter(int64_t cost, int32_t steps, const DPPoint *prev, int32_t n, int32_t sig_x,
90 int64_t sig_xsq);
91
92 int32_t local_cost_; // Cost of this point on its own.
93 int32_t total_cost_; // Sum of all costs in best path to here.
94 // During cost calculations local_cost is excluded.
95 int32_t total_steps_; // Number of steps in best path to here.
96 const DPPoint *best_prev_; // Pointer to prev point in best path from here.
97 // Information for computing the variance part of the cost.
98 int32_t n_; // Number of steps in best path to here for variance.
99 int32_t sig_x_; // Sum of step sizes for computing variance.
100 int64_t sig_xsq_; // Sum of squares of steps for computing variance.
101 };
102
103 } // namespace tesseract.
104
105 #endif // TESSERACT_CCSTRUCT_DPPOINT_H_