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https://github.com/tesseract-ocr/tesseract.git
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d35a6f2de5
Signed-off-by: Stefan Weil <sw@weilnetz.de>
160 lines
7.9 KiB
C++
160 lines
7.9 KiB
C++
///////////////////////////////////////////////////////////////////////
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// File: imagefind.h
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// Description: Class to find image and drawing regions in an image
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// and create a corresponding list of empty blobs.
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// Author: Ray Smith
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//
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// (C) Copyright 2008, Google Inc.
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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///////////////////////////////////////////////////////////////////////
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#ifndef TESSERACT_TEXTORD_IMAGEFIND_H_
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#define TESSERACT_TEXTORD_IMAGEFIND_H_
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#include "debugpixa.h"
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#include <cstdint>
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struct Boxa;
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struct Pix;
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struct Pixa;
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class TBOX;
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class FCOORD;
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class TO_BLOCK;
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class BLOBNBOX_LIST;
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namespace tesseract {
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class ColPartitionGrid;
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class ColPartition_LIST;
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class TabFind;
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// The ImageFind class is a simple static function wrapper class that
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// exposes the FindImages function and some useful helper functions.
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class ImageFind {
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public:
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// Finds image regions within the BINARY source pix (page image) and returns
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// the image regions as a mask image.
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// The returned pix may be nullptr, meaning no images found.
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// If not nullptr, it must be PixDestroyed by the caller.
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// If textord_tabfind_show_images, debug images are appended to pixa_debug.
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static Pix* FindImages(Pix* pix, DebugPixa* pixa_debug);
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// Generates a Boxa, Pixa pair from the input binary (image mask) pix,
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// analgous to pixConnComp, except that connected components which are nearly
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// rectangular are replaced with solid rectangles.
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// The returned boxa, pixa may be nullptr, meaning no images found.
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// If not nullptr, they must be destroyed by the caller.
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// Resolution of pix should match the source image (Tesseract::pix_binary_)
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// so the output coordinate systems match.
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static void ConnCompAndRectangularize(Pix* pix, DebugPixa* pixa_debug,
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Boxa** boxa, Pixa** pixa);
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// Returns true if there is a rectangle in the source pix, such that all
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// pixel rows and column slices outside of it have less than
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// min_fraction of the pixels black, and within max_skew_gradient fraction
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// of the pixels on the inside, there are at least max_fraction of the
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// pixels black. In other words, the inside of the rectangle looks roughly
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// rectangular, and the outside of it looks like extra bits.
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// On return, the rectangle is defined by x_start, y_start, x_end and y_end.
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// Note: the algorithm is iterative, allowing it to slice off pixels from
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// one edge, allowing it to then slice off more pixels from another edge.
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static bool pixNearlyRectangular(Pix* pix,
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double min_fraction, double max_fraction,
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double max_skew_gradient,
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int* x_start, int* y_start,
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int* x_end, int* y_end);
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// Given an input pix, and a bounding rectangle, the sides of the rectangle
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// are shrunk inwards until they bound any black pixels found within the
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// original rectangle. Returns false if the rectangle contains no black
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// pixels at all.
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static bool BoundsWithinRect(Pix* pix, int* x_start, int* y_start,
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int* x_end, int* y_end);
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// Given a point in 3-D (RGB) space, returns the squared Euclidean distance
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// of the point from the given line, defined by a pair of points in the 3-D
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// (RGB) space, line1 and line2.
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static double ColorDistanceFromLine(const uint8_t* line1, const uint8_t* line2,
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const uint8_t* point);
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// Returns the leptonica combined code for the given RGB triplet.
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static uint32_t ComposeRGB(uint32_t r, uint32_t g, uint32_t b);
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// Returns the input value clipped to a uint8_t.
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static uint8_t ClipToByte(double pixel);
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// Computes the light and dark extremes of color in the given rectangle of
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// the given pix, which is factor smaller than the coordinate system in rect.
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// The light and dark points are taken to be the upper and lower 8th-ile of
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// the most deviant of R, G and B. The value of the other 2 channels are
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// computed by linear fit against the most deviant.
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// The colors of the two point are returned in color1 and color2, with the
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// alpha channel set to a scaled mean rms of the fits.
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// If color_map1 is not null then it and color_map2 get rect pasted in them
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// with the two calculated colors, and rms map gets a pasted rect of the rms.
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// color_map1, color_map2 and rms_map are assumed to be the same scale as pix.
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static void ComputeRectangleColors(const TBOX& rect, Pix* pix, int factor,
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Pix* color_map1, Pix* color_map2,
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Pix* rms_map,
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uint8_t* color1, uint8_t* color2);
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// Returns true if there are no black pixels in between the boxes.
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// The im_box must represent the bounding box of the pix in tesseract
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// coordinates, which may be negative, due to rotations to make the textlines
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// horizontal. The boxes are rotated by rotation, which should undo such
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// rotations, before mapping them onto the pix.
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static bool BlankImageInBetween(const TBOX& box1, const TBOX& box2,
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const TBOX& im_box, const FCOORD& rotation,
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Pix* pix);
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// Returns the number of pixels in box in the pix.
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// The im_box must represent the bounding box of the pix in tesseract
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// coordinates, which may be negative, due to rotations to make the textlines
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// horizontal. The boxes are rotated by rotation, which should undo such
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// rotations, before mapping them onto the pix.
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static int CountPixelsInRotatedBox(TBOX box, const TBOX& im_box,
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const FCOORD& rotation, Pix* pix);
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// Locates all the image partitions in the part_grid, that were found by a
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// previous call to FindImagePartitions, marks them in the image_mask,
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// removes them from the grid, and deletes them. This makes it possible to
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// call FindImagePartitions again to produce less broken-up and less
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// overlapping image partitions.
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// rerotation specifies how to rotate the partition coords to match
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// the image_mask, since this function is used after orientation correction.
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static void TransferImagePartsToImageMask(const FCOORD& rerotation,
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ColPartitionGrid* part_grid,
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Pix* image_mask);
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// Runs a CC analysis on the image_pix mask image, and creates
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// image partitions from them, cutting out strong text, and merging with
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// nearby image regions such that they don't interfere with text.
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// Rotation and rerotation specify how to rotate image coords to match
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// the blob and partition coords and back again.
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// The input/output part_grid owns all the created partitions, and
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// the partitions own all the fake blobs that belong in the partitions.
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// Since the other blobs in the other partitions will be owned by the block,
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// ColPartitionGrid::ReTypeBlobs must be called afterwards to fix this
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// situation and collect the image blobs.
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static void FindImagePartitions(Pix* image_pix, const FCOORD& rotation,
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const FCOORD& rerotation, TO_BLOCK* block,
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TabFind* tab_grid, DebugPixa* pixa_debug,
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ColPartitionGrid* part_grid,
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ColPartition_LIST* big_parts);
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};
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} // namespace tesseract.
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#endif // TESSERACT_TEXTORD_LINEFIND_H_
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