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comparison mupdf-source/thirdparty/tesseract/src/ccstruct/otsuthr.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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1:1d09e1dec1d9 2:b50eed0cc0ef
1 ///////////////////////////////////////////////////////////////////////
2 // File: otsuthr.h
3 // Description: Simple Otsu thresholding for binarizing images.
4 // Author: Ray Smith
5 //
6 // (C) Copyright 2008, Google Inc.
7 // Licensed under the Apache License, Version 2.0 (the "License");
8 // you may not use this file except in compliance with the License.
9 // You may obtain a copy of the License at
10 // http://www.apache.org/licenses/LICENSE-2.0
11 // Unless required by applicable law or agreed to in writing, software
12 // distributed under the License is distributed on an "AS IS" BASIS,
13 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 // See the License for the specific language governing permissions and
15 // limitations under the License.
16 //
17 ///////////////////////////////////////////////////////////////////////
18
19 #ifndef TESSERACT_CCMAIN_OTSUTHR_H_
20 #define TESSERACT_CCMAIN_OTSUTHR_H_
21
22 #include "image.h"
23
24 #include <vector> // for std::vector
25
26 struct Pix;
27
28 namespace tesseract {
29
30 const int kHistogramSize = 256; // The size of a histogram of pixel values.
31
32 // Computes the Otsu threshold(s) for the given image rectangle, making one
33 // for each channel. Each channel is always one byte per pixel.
34 // Returns an array of threshold values and an array of hi_values, such
35 // that a pixel value >threshold[channel] is considered foreground if
36 // hi_values[channel] is 0 or background if 1. A hi_value of -1 indicates
37 // that there is no apparent foreground. At least one hi_value will not be -1.
38 // The return value is the number of channels in the input image, being
39 // the size of the output thresholds and hi_values arrays.
40 int OtsuThreshold(Image src_pix, int left, int top, int width, int height,
41 std::vector<int> &thresholds,
42 std::vector<int> &hi_values);
43
44 // Computes the histogram for the given image rectangle, and the given
45 // single channel. Each channel is always one byte per pixel.
46 // Histogram is always a kHistogramSize(256) element array to count
47 // occurrences of each pixel value.
48 void HistogramRect(Image src_pix, int channel, int left, int top, int width, int height,
49 int *histogram);
50
51 // Computes the Otsu threshold(s) for the given histogram.
52 // Also returns H = total count in histogram, and
53 // omega0 = count of histogram below threshold.
54 int OtsuStats(const int *histogram, int *H_out, int *omega0_out);
55
56 } // namespace tesseract.
57
58 #endif // TESSERACT_CCMAIN_OTSUTHR_H_