--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/tesseract/src/textord/colfind.h	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,357 @@
+///////////////////////////////////////////////////////////////////////
+// File:        colfind.h
+// Description: Class to find columns in the grid of BLOBNBOXes.
+// Author:      Ray Smith
+//
+// (C) Copyright 2008, Google Inc.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+///////////////////////////////////////////////////////////////////////
+
+#ifndef TESSERACT_TEXTORD_COLFIND_H_
+#define TESSERACT_TEXTORD_COLFIND_H_
+
+#include "colpartitiongrid.h"
+#include "colpartitionset.h"
+#include "debugpixa.h"
+#include "imagefind.h"
+#include "ocrblock.h"
+#include "tabfind.h"
+#include "textlineprojection.h"
+
+class BLOCK_LIST;
+struct Boxa;
+struct Pixa;
+class DENORM;
+class ScrollView;
+class STATS;
+class TO_BLOCK;
+
+namespace tesseract {
+
+class ColPartitionSet;
+class ColPartitionSet_LIST;
+class ColSegment_LIST;
+class ColumnGroup_LIST;
+class LineSpacing;
+class StrokeWidth;
+class TempColumn_LIST;
+class EquationDetectBase;
+
+// The ColumnFinder class finds columns in the grid.
+class TESS_API ColumnFinder : public TabFind {
+public:
+  // Gridsize is an estimate of the text size in the image. A suitable value
+  // is in TO_BLOCK::line_size after find_components has been used to make
+  // the blobs.
+  // bleft and tright are the bounds of the image (rectangle) being processed.
+  // vlines is a (possibly empty) list of TabVector and vertical_x and y are
+  // the sum logical vertical vector produced by LineFinder::FindVerticalLines.
+  // If cjk_script is true, then broken CJK characters are fixed during
+  // layout analysis to assist in detecting horizontal vs vertically written
+  // textlines.
+  ColumnFinder(int gridsize, const ICOORD &bleft, const ICOORD &tright, int resolution,
+               bool cjk_script, double aligned_gap_fraction, TabVector_LIST *vlines,
+               TabVector_LIST *hlines, int vertical_x, int vertical_y);
+  ~ColumnFinder() override;
+
+  // Accessors for testing
+  const DENORM *denorm() const {
+    return denorm_;
+  }
+  const TextlineProjection *projection() const {
+    return &projection_;
+  }
+  void set_cjk_script(bool is_cjk) {
+    cjk_script_ = is_cjk;
+  }
+
+  // ======================================================================
+  // The main function of ColumnFinder is broken into pieces to facilitate
+  // optional insertion of orientation and script detection in an efficient
+  // way. The calling sequence IS MANDATORY however, whether or not
+  // OSD is being used:
+  // 1. Construction.
+  // 2. SetupAndFilterNoise.
+  // 3. IsVerticallyAlignedText.
+  // 4. CorrectOrientation.
+  // 5. FindBlocks.
+  // 6. Destruction. Use of a single column finder for multiple images does not
+  //    make sense.
+  // Throughout these steps, the ColPartitions are owned by part_grid_, which
+  // means that it must be kept correct. Exception: big_parts_ owns its
+  // own ColPartitions.
+  // The BLOBNBOXes are owned by the input TO_BLOCK for the whole time, except
+  // for a phase in FindBlocks before TransformToBlocks, when they become
+  // owned by the ColPartitions. The owner() ColPartition of a BLOBNBOX
+  // indicates more of a betrothal for the majority of layout analysis, ie
+  // which ColPartition will take ownership when the blobs are release from
+  // the input TO_BLOCK. Exception: image_bblobs_ owns the fake blobs that
+  // are part of the image regions, as they are not on any TO_BLOCK list.
+  // TODO(rays) break up column finder further into smaller classes, as
+  // there is a lot more to it than column finding now.
+  // ======================================================================
+
+  // Performs initial processing on the blobs in the input_block:
+  // Setup the part_grid, stroke_width_, nontext_map_.
+  // Obvious noise blobs are filtered out and used to mark the nontext_map_.
+  // Initial stroke-width analysis is used to get local text alignment
+  // direction, so the textline projection_ map can be setup.
+  // On return, IsVerticallyAlignedText may be called (now optionally) to
+  // determine the gross textline alignment of the page.
+  void SetupAndFilterNoise(PageSegMode pageseg_mode, Image photo_mask_pix, TO_BLOCK *input_block);
+
+  // Tests for vertical alignment of text (returning true if so), and generates
+  // a list of blobs (in osd_blobs) for orientation and script detection.
+  // block is the single block for the whole page or rectangle to be OCRed.
+  // Note that the vertical alignment may be due to text whose writing direction
+  // is vertical, like say Japanese, or due to text whose writing direction is
+  // horizontal but whose text appears vertically aligned because the image is
+  // not the right way up.
+  // find_vertical_text_ratio should be textord_tabfind_vertical_text_ratio.
+  bool IsVerticallyAlignedText(double find_vertical_text_ratio, TO_BLOCK *block,
+                               BLOBNBOX_CLIST *osd_blobs);
+
+  // Rotates the blobs and the TabVectors so that the gross writing direction
+  // (text lines) are horizontal and lines are read down the page.
+  // Applied rotation stored in rotation_.
+  // A second rotation is calculated for application during recognition to
+  // make the rotated blobs upright for recognition.
+  // Subsequent rotation stored in text_rotation_.
+  //
+  // Arguments:
+  //   vertical_text_lines is true if the text lines are vertical.
+  //   recognition_rotation [0..3] is the number of anti-clockwise 90 degree
+  //   rotations from osd required for the text to be upright and readable.
+  void CorrectOrientation(TO_BLOCK *block, bool vertical_text_lines, int recognition_rotation);
+
+  // Finds blocks of text, image, rule line, table etc, returning them in the
+  // blocks and to_blocks
+  // (Each TO_BLOCK points to the basic BLOCK and adds more information.)
+  // Image blocks are generated by a combination of photo_mask_pix (which may
+  // NOT be nullptr) and the rejected text found during preliminary textline
+  // finding.
+  // The input_block is the result of a call to find_components, and contains
+  // the blobs found in the image or rectangle to be OCRed. These blobs will be
+  // removed and placed in the output blocks, while unused ones will be deleted.
+  // If single_column is true, the input is treated as single column, but
+  // it is still divided into blocks of equal line spacing/text size.
+  // scaled_color is scaled down by scaled_factor from the input color image,
+  // and may be nullptr if the input was not color.
+  // grey_pix is optional, but if present must match the photo_mask_pix in size,
+  // and must be a *real* grey image instead of binary_pix * 255.
+  // thresholds_pix is expected to be present iff grey_pix is present and
+  // can be an integer factor reduction of the grey_pix. It represents the
+  // thresholds that were used to create the binary_pix from the grey_pix.
+  // Small blobs that confuse the segmentation into lines are placed into
+  // diacritic_blobs, with the intention that they be put into the most
+  // appropriate word after the rest of layout analysis.
+  // Returns -1 if the user hits the 'd' key in the blocks window while running
+  // in debug mode, which requests a retry with more debug info.
+  int FindBlocks(PageSegMode pageseg_mode, Image scaled_color, int scaled_factor, TO_BLOCK *block,
+                 Image photo_mask_pix, Image thresholds_pix, Image grey_pix, DebugPixa *pixa_debug,
+                 BLOCK_LIST *blocks, BLOBNBOX_LIST *diacritic_blobs, TO_BLOCK_LIST *to_blocks);
+
+  // Get the rotation required to deskew, and its inverse rotation.
+  void GetDeskewVectors(FCOORD *deskew, FCOORD *reskew);
+
+  // Set the equation detection pointer.
+  void SetEquationDetect(EquationDetectBase *detect);
+
+private:
+  // Displays the blob and block bounding boxes in a window called Blocks.
+  void DisplayBlocks(BLOCK_LIST *blocks);
+  // Displays the column edges at each grid y coordinate defined by
+  // best_columns_.
+  void DisplayColumnBounds(PartSetVector *sets);
+
+  ////// Functions involved in determining the columns used on the page. /////
+
+  // Sets up column_sets_ (the determined column layout at each horizontal
+  // slice). Returns false if the page is empty.
+  bool MakeColumns(bool single_column);
+  // Attempt to improve the column_candidates by expanding the columns
+  // and adding new partitions from the partition sets in src_sets.
+  // Src_sets may be equal to column_candidates, in which case it will
+  // use them as a source to improve themselves.
+  void ImproveColumnCandidates(PartSetVector *src_sets, PartSetVector *column_sets);
+  // Prints debug information on the column candidates.
+  void PrintColumnCandidates(const char *title);
+  // Finds the optimal set of columns that cover the entire image with as
+  // few changes in column partition as possible.
+  // Returns true if any part of the page is multi-column.
+  bool AssignColumns(const PartSetVector &part_sets);
+  // Finds the biggest range in part_sets_ that has no assigned column, but
+  // column assignment is possible.
+  bool BiggestUnassignedRange(int set_count, const bool *any_columns_possible, int *start,
+                              int *end);
+  // Finds the modal compatible column_set_ index within the given range.
+  int RangeModalColumnSet(int **column_set_costs, const int *assigned_costs, int start, int end);
+  // Given that there are many column_set_id compatible columns in the range,
+  // shrinks the range to the longest contiguous run of compatibility, allowing
+  // gaps where no columns are possible, but not where competing columns are
+  // possible.
+  void ShrinkRangeToLongestRun(int **column_set_costs, const int *assigned_costs,
+                               const bool *any_columns_possible, int column_set_id, int *best_start,
+                               int *best_end);
+  // Moves start in the direction of step, up to, but not including end while
+  // the only incompatible regions are no more than kMaxIncompatibleColumnCount
+  // in size, and the compatible regions beyond are bigger.
+  void ExtendRangePastSmallGaps(int **column_set_costs, const int *assigned_costs,
+                                const bool *any_columns_possible, int column_set_id, int step,
+                                int end, int *start);
+  // Assigns the given column_set_id to the part_sets_ in the given range.
+  void AssignColumnToRange(int column_set_id, int start, int end, int **column_set_costs,
+                           int *assigned_costs);
+
+  // Computes the mean_column_gap_.
+  void ComputeMeanColumnGap(bool any_multi_column);
+
+  //////// Functions that manipulate ColPartitions in the part_grid_ /////
+  //////// to split, merge, find margins, and find types.  //////////////
+
+  // Hoovers up all un-owned blobs and deletes them.
+  // The rest get released from the block so the ColPartitions can pass
+  // ownership to the output blocks.
+  void ReleaseBlobsAndCleanupUnused(TO_BLOCK *block);
+  // Splits partitions that cross columns where they have nothing in the gap.
+  void GridSplitPartitions();
+  // Merges partitions where there is vertical overlap, within a single column,
+  // and the horizontal gap is small enough.
+  void GridMergePartitions();
+  // Inserts remaining noise blobs into the most applicable partition if any.
+  // If there is no applicable partition, then the blobs are deleted.
+  void InsertRemainingNoise(TO_BLOCK *block);
+  // Remove partitions that come from horizontal lines that look like
+  // underlines, but are not part of a table.
+  void GridRemoveUnderlinePartitions();
+  // Add horizontal line separators as partitions.
+  void GridInsertHLinePartitions();
+  // Add vertical line separators as partitions.
+  void GridInsertVLinePartitions();
+  // For every ColPartition in the grid, sets its type based on position
+  // in the columns.
+  void SetPartitionTypes();
+  // Only images remain with multiple types in a run of partners.
+  // Sets the type of all in the group to the maximum of the group.
+  void SmoothPartnerRuns();
+
+  //////// Functions that make the final output blocks             ///////
+
+  // Helper functions for TransformToBlocks.
+  // Add the part to the temp list in the correct order.
+  void AddToTempPartList(ColPartition *part, ColPartition_CLIST *temp_list);
+  // Add everything from the temp list to the work_set assuming correct order.
+  void EmptyTempPartList(ColPartition_CLIST *temp_list, WorkingPartSet_LIST *work_set);
+
+  // Transform the grid of partitions to the output blocks.
+  void TransformToBlocks(BLOCK_LIST *blocks, TO_BLOCK_LIST *to_blocks);
+
+  // Reflect the blob boxes (but not the outlines) in the y-axis so that
+  // the blocks get created in the correct RTL order. Rotates the blobs
+  // in the input_block and the bblobs list.
+  // The reflection is undone in RotateAndReskewBlocks by
+  // reflecting the blocks themselves, and then recomputing the blob bounding
+  //  boxes.
+  void ReflectForRtl(TO_BLOCK *input_block, BLOBNBOX_LIST *bblobs);
+
+  // Undo the deskew that was done in FindTabVectors, as recognition is done
+  // without correcting blobs or blob outlines for skew.
+  // Reskew the completed blocks to put them back to the original rotated coords
+  // that were created by CorrectOrientation.
+  // If the input_is_rtl, then reflect the blocks in the y-axis to undo the
+  // reflection that was done before FindTabVectors.
+  // Blocks that were identified as vertical text (relative to the rotated
+  // coordinates) are further rotated so the text lines are horizontal.
+  // blob polygonal outlines are rotated to match the position of the blocks
+  // that they are in, and their bounding boxes are recalculated to be accurate.
+  // Record appropriate inverse transformations and required
+  // classifier transformation in the blocks.
+  void RotateAndReskewBlocks(bool input_is_rtl, TO_BLOCK_LIST *to_blocks);
+
+  // Computes the rotations for the block (to make textlines horizontal) and
+  // for the blobs (for classification) and sets the appropriate members
+  // of the given block.
+  // Returns the rotation that needs to be applied to the blobs to make
+  // them sit in the rotated block.
+  FCOORD ComputeBlockAndClassifyRotation(BLOCK *block);
+
+  // If true then the page language is cjk, so it is safe to perform
+  // FixBrokenCJK.
+  bool cjk_script_;
+  // The minimum gutter width to apply for finding columns.
+  // Modified when vertical text is detected to prevent detection of
+  // vertical text lines as columns.
+  int min_gutter_width_;
+  // The mean gap between columns over the page.
+  int mean_column_gap_;
+  // Config param saved at construction time. Modifies min_gutter_width_ with
+  // vertical text to prevent detection of vertical text as columns.
+  double tabfind_aligned_gap_fraction_;
+  // The rotation vector needed to convert original coords to deskewed.
+  FCOORD deskew_;
+  // The rotation vector needed to convert deskewed back to original coords.
+  FCOORD reskew_;
+  // The rotation vector used to rotate vertically oriented pages.
+  FCOORD rotation_;
+  // The rotation vector needed to convert the rotated back to original coords.
+  FCOORD rerotate_;
+  // The additional rotation vector needed to rotate text for recognition.
+  FCOORD text_rotation_;
+  // The column_sets_ contain the ordered candidate ColPartitionSets that
+  // define the possible divisions of the page into columns.
+  PartSetVector column_sets_;
+  // A simple array of pointers to the best assigned column division at
+  // each grid y coordinate.
+  ColPartitionSet **best_columns_;
+  // The grid used for creating initial partitions with strokewidth.
+  StrokeWidth *stroke_width_;
+  // The grid used to hold ColPartitions after the columns have been determined.
+  ColPartitionGrid part_grid_;
+  // List of ColPartitions that are no longer needed after they have been
+  // turned into regions, but are kept around because they are referenced
+  // by the part_grid_.
+  ColPartition_LIST good_parts_;
+  // List of ColPartitions that are big and might be dropcap or vertically
+  // joined.
+  ColPartition_LIST big_parts_;
+  // List of ColPartitions that have been declared noise.
+  ColPartition_LIST noise_parts_;
+  // The fake blobs that are made from the images.
+  BLOBNBOX_LIST image_bblobs_;
+  // Horizontal line separators.
+  TabVector_LIST horizontal_lines_;
+  // Image map of photo/noise areas on the page.
+  Image nontext_map_;
+  // Textline projection map.
+  TextlineProjection projection_;
+  // Sequence of DENORMS that indicate how to get back to the original image
+  // coordinate space. The destructor must delete all the DENORMs in the chain.
+  DENORM *denorm_;
+
+  // The equation region detector pointer. Note: This pointer is passed in by
+  // member function SetEquationDetect, and releasing it is NOT owned by this
+  // class.
+  EquationDetectBase *equation_detect_;
+
+#ifndef GRAPHICS_DISABLED
+  // Various debug windows that automatically go away on completion.
+  ScrollView *input_blobs_win_ = nullptr;
+
+  // Allow a subsequent instance to reuse the blocks window.
+  // Not thread-safe, but multiple threads shouldn't be using windows anyway.
+  static ScrollView *blocks_win_;
+#endif
+};
+
+} // namespace tesseract.
+
+#endif // TESSERACT_TEXTORD_COLFIND_H_