tesseract  5.0.0
ccnontextdetect.h
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1 // File: ccnontextdetect.h
3 // Description: Connected-Component-based non-text detection.
4 // Copyright 2011 Google Inc. All Rights Reserved.
5 // Author: rays@google.com (Ray Smith)
6 // Created: Sat Jun 11 09:52:01 PST 2011
7 //
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 //
19 
20 #ifndef TESSERACT_TEXTORD_CCPHOTODETECT_H_
21 #define TESSERACT_TEXTORD_CCPHOTODETECT_H_
22 
23 #include "blobgrid.h"
24 #include "scrollview.h"
25 
26 namespace tesseract {
27 
28 // The CCNonTextDetect class contains grid-based operations on blobs to create
29 // a full-resolution image mask analogous yet complementary to
30 // pixGenHalftoneMask as it is better at line-drawings, graphs and charts.
31 class CCNonTextDetect : public BlobGrid {
32 public:
33  CCNonTextDetect(int gridsize, const ICOORD &bleft, const ICOORD &tright);
34  ~CCNonTextDetect() override;
35 
36  // Creates and returns a Pix with the same resolution as the original
37  // in which 1 (black) pixels represent likely non text (photo, line drawing)
38  // areas of the page, deleting from the blob_block the blobs that were
39  // determined to be non-text.
40  // The photo_map (binary image mask) is used to bias the decision towards
41  // non-text, rather than supplying a definite decision.
42  // The blob_block is the usual result of connected component analysis,
43  // holding the detected blobs.
44  // The returned Pix should be PixDestroyed after use.
45  Image ComputeNonTextMask(bool debug, Image photo_map, TO_BLOCK *blob_block);
46 
47 private:
48  // Computes and returns the noise_density IntGrid, at the same gridsize as
49  // this by summing the number of small elements in a 3x3 neighbourhood of
50  // each grid cell. good_grid is filled with blobs that are considered most
51  // likely good text, and this is filled with small and medium blobs that are
52  // more likely non-text.
53  // The photo_map is used to bias the decision towards non-text, rather than
54  // supplying definite decision.
55  IntGrid *ComputeNoiseDensity(bool debug, Image photo_map, BlobGrid *good_grid);
56 
57  // Tests each blob in the list to see if it is certain non-text using 2
58  // conditions:
59  // 1. blob overlaps a cell with high value in noise_density_ (previously set
60  // by ComputeNoiseDensity).
61  // OR 2. The blob overlaps more than max_blob_overlaps in *this grid. This
62  // condition is disabled with max_blob_overlaps == -1.
63  // If it does, the blob is declared non-text, and is used to mark up the
64  // nontext_mask. Such blobs are fully deleted, and non-noise blobs have their
65  // neighbours reset, as they may now point to deleted data.
66  // WARNING: The blobs list blobs may be in the *this grid, but they are
67  // not removed. If any deleted blobs might be in *this, then this must be
68  // Clear()ed immediately after MarkAndDeleteNonTextBlobs is called.
69  // If the win is not nullptr, deleted blobs are drawn on it in red, and kept
70  void MarkAndDeleteNonTextBlobs(BLOBNBOX_LIST *blobs, int max_blob_overlaps, ScrollView *win,
71  ScrollView::Color ok_color, Image nontext_mask);
72  // Returns true if the given blob overlaps more than max_overlaps blobs
73  // in the current grid.
74  bool BlobOverlapsTooMuch(BLOBNBOX *blob, int max_overlaps);
75 
76  // Max entry in noise_density_ before the cell is declared noisy.
77  int max_noise_count_;
78  // Completed noise density map, which we keep around to use for secondary
79  // noise detection.
80  IntGrid *noise_density_;
81 };
82 
83 } // namespace tesseract.
84 
85 #endif // TESSERACT_TEXTORD_CCPHOTODETECT_H_
integer coordinate
Definition: points.h:36
int gridsize() const
Definition: bbgrid.h:63
const ICOORD & bleft() const
Definition: bbgrid.h:72
const ICOORD & tright() const
Definition: bbgrid.h:75
CCNonTextDetect(int gridsize, const ICOORD &bleft, const ICOORD &tright)
Image ComputeNonTextMask(bool debug, Image photo_map, TO_BLOCK *blob_block)