tesseract 4.1.1
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imagefind.h
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1
2// File: imagefind.h
3// Description: Class to find image and drawing regions in an image
4// and create a corresponding list of empty blobs.
5// Author: Ray Smith
6//
7// (C) Copyright 2008, 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//
19
20#ifndef TESSERACT_TEXTORD_IMAGEFIND_H_
21#define TESSERACT_TEXTORD_IMAGEFIND_H_
22
23#include "debugpixa.h"
24
25#include <cstdint>
26
27struct Boxa;
28struct Pix;
29struct Pixa;
30class TBOX;
31class FCOORD;
32class TO_BLOCK;
33class BLOBNBOX_LIST;
34
35namespace tesseract {
36
37class ColPartitionGrid;
38class ColPartition_LIST;
39class TabFind;
40
41// The ImageFind class is a simple static function wrapper class that
42// exposes the FindImages function and some useful helper functions.
43class ImageFind {
44 public:
45 // Finds image regions within the BINARY source pix (page image) and returns
46 // the image regions as a mask image.
47 // The returned pix may be nullptr, meaning no images found.
48 // If not nullptr, it must be PixDestroyed by the caller.
49 // If textord_tabfind_show_images, debug images are appended to pixa_debug.
50 static Pix* FindImages(Pix* pix, DebugPixa* pixa_debug);
51
52 // Generates a Boxa, Pixa pair from the input binary (image mask) pix,
53 // analgous to pixConnComp, except that connected components which are nearly
54 // rectangular are replaced with solid rectangles.
55 // The returned boxa, pixa may be nullptr, meaning no images found.
56 // If not nullptr, they must be destroyed by the caller.
57 // Resolution of pix should match the source image (Tesseract::pix_binary_)
58 // so the output coordinate systems match.
59 static void ConnCompAndRectangularize(Pix* pix, DebugPixa* pixa_debug,
60 Boxa** boxa, Pixa** pixa);
61
62 // Returns true if there is a rectangle in the source pix, such that all
63 // pixel rows and column slices outside of it have less than
64 // min_fraction of the pixels black, and within max_skew_gradient fraction
65 // of the pixels on the inside, there are at least max_fraction of the
66 // pixels black. In other words, the inside of the rectangle looks roughly
67 // rectangular, and the outside of it looks like extra bits.
68 // On return, the rectangle is defined by x_start, y_start, x_end and y_end.
69 // Note: the algorithm is iterative, allowing it to slice off pixels from
70 // one edge, allowing it to then slice off more pixels from another edge.
71 static bool pixNearlyRectangular(Pix* pix,
72 double min_fraction, double max_fraction,
73 double max_skew_gradient,
74 int* x_start, int* y_start,
75 int* x_end, int* y_end);
76
77 // Given an input pix, and a bounding rectangle, the sides of the rectangle
78 // are shrunk inwards until they bound any black pixels found within the
79 // original rectangle. Returns false if the rectangle contains no black
80 // pixels at all.
81 static bool BoundsWithinRect(Pix* pix, int* x_start, int* y_start,
82 int* x_end, int* y_end);
83
84 // Given a point in 3-D (RGB) space, returns the squared Euclidean distance
85 // of the point from the given line, defined by a pair of points in the 3-D
86 // (RGB) space, line1 and line2.
87 static double ColorDistanceFromLine(const uint8_t* line1, const uint8_t* line2,
88 const uint8_t* point);
89
90 // Returns the leptonica combined code for the given RGB triplet.
91 static uint32_t ComposeRGB(uint32_t r, uint32_t g, uint32_t b);
92
93 // Returns the input value clipped to a uint8_t.
94 static uint8_t ClipToByte(double pixel);
95
96 // Computes the light and dark extremes of color in the given rectangle of
97 // the given pix, which is factor smaller than the coordinate system in rect.
98 // The light and dark points are taken to be the upper and lower 8th-ile of
99 // the most deviant of R, G and B. The value of the other 2 channels are
100 // computed by linear fit against the most deviant.
101 // The colors of the two point are returned in color1 and color2, with the
102 // alpha channel set to a scaled mean rms of the fits.
103 // If color_map1 is not null then it and color_map2 get rect pasted in them
104 // with the two calculated colors, and rms map gets a pasted rect of the rms.
105 // color_map1, color_map2 and rms_map are assumed to be the same scale as pix.
106 static void ComputeRectangleColors(const TBOX& rect, Pix* pix, int factor,
107 Pix* color_map1, Pix* color_map2,
108 Pix* rms_map,
109 uint8_t* color1, uint8_t* color2);
110
111 // Returns true if there are no black pixels in between the boxes.
112 // The im_box must represent the bounding box of the pix in tesseract
113 // coordinates, which may be negative, due to rotations to make the textlines
114 // horizontal. The boxes are rotated by rotation, which should undo such
115 // rotations, before mapping them onto the pix.
116 static bool BlankImageInBetween(const TBOX& box1, const TBOX& box2,
117 const TBOX& im_box, const FCOORD& rotation,
118 Pix* pix);
119
120 // Returns the number of pixels in box in the pix.
121 // The im_box must represent the bounding box of the pix in tesseract
122 // coordinates, which may be negative, due to rotations to make the textlines
123 // horizontal. The boxes are rotated by rotation, which should undo such
124 // rotations, before mapping them onto the pix.
125 static int CountPixelsInRotatedBox(TBOX box, const TBOX& im_box,
126 const FCOORD& rotation, Pix* pix);
127
128
129 // Locates all the image partitions in the part_grid, that were found by a
130 // previous call to FindImagePartitions, marks them in the image_mask,
131 // removes them from the grid, and deletes them. This makes it possible to
132 // call FindImagePartitions again to produce less broken-up and less
133 // overlapping image partitions.
134 // rerotation specifies how to rotate the partition coords to match
135 // the image_mask, since this function is used after orientation correction.
136 static void TransferImagePartsToImageMask(const FCOORD& rerotation,
137 ColPartitionGrid* part_grid,
138 Pix* image_mask);
139
140 // Runs a CC analysis on the image_pix mask image, and creates
141 // image partitions from them, cutting out strong text, and merging with
142 // nearby image regions such that they don't interfere with text.
143 // Rotation and rerotation specify how to rotate image coords to match
144 // the blob and partition coords and back again.
145 // The input/output part_grid owns all the created partitions, and
146 // the partitions own all the fake blobs that belong in the partitions.
147 // Since the other blobs in the other partitions will be owned by the block,
148 // ColPartitionGrid::ReTypeBlobs must be called afterwards to fix this
149 // situation and collect the image blobs.
150 static void FindImagePartitions(Pix* image_pix, const FCOORD& rotation,
151 const FCOORD& rerotation, TO_BLOCK* block,
152 TabFind* tab_grid, DebugPixa* pixa_debug,
153 ColPartitionGrid* part_grid,
154 ColPartition_LIST* big_parts);
155};
156
157} // namespace tesseract.
158
159#endif // TESSERACT_TEXTORD_LINEFIND_H_
Definition: points.h:189
Definition: rect.h:34
static void FindImagePartitions(Pix *image_pix, const FCOORD &rotation, const FCOORD &rerotation, TO_BLOCK *block, TabFind *tab_grid, DebugPixa *pixa_debug, ColPartitionGrid *part_grid, ColPartition_LIST *big_parts)
Definition: imagefind.cpp:1298
static void ComputeRectangleColors(const TBOX &rect, Pix *pix, int factor, Pix *color_map1, Pix *color_map2, Pix *rms_map, uint8_t *color1, uint8_t *color2)
Definition: imagefind.cpp:414
static bool pixNearlyRectangular(Pix *pix, double min_fraction, double max_fraction, double max_skew_gradient, int *x_start, int *y_start, int *x_end, int *y_end)
Definition: imagefind.cpp:266
static int CountPixelsInRotatedBox(TBOX box, const TBOX &im_box, const FCOORD &rotation, Pix *pix)
Definition: imagefind.cpp:597
static bool BlankImageInBetween(const TBOX &box1, const TBOX &box2, const TBOX &im_box, const FCOORD &rotation, Pix *pix)
Definition: imagefind.cpp:576
static void ConnCompAndRectangularize(Pix *pix, DebugPixa *pixa_debug, Boxa **boxa, Pixa **pixa)
Definition: imagefind.cpp:154
static bool BoundsWithinRect(Pix *pix, int *x_start, int *y_start, int *x_end, int *y_end)
Definition: imagefind.cpp:332
static Pix * FindImages(Pix *pix, DebugPixa *pixa_debug)
Definition: imagefind.cpp:62
static uint32_t ComposeRGB(uint32_t r, uint32_t g, uint32_t b)
Definition: imagefind.cpp:389
static uint8_t ClipToByte(double pixel)
Definition: imagefind.cpp:396
static double ColorDistanceFromLine(const uint8_t *line1, const uint8_t *line2, const uint8_t *point)
Definition: imagefind.cpp:355
static void TransferImagePartsToImageMask(const FCOORD &rerotation, ColPartitionGrid *part_grid, Pix *image_mask)
Definition: imagefind.cpp:1245