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tesseract/ccmain/pagesegmain.cpp

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/**********************************************************************
* File: pagesegmain.cpp
* Description: Top-level page segmenter for Tesseract.
* Author: Ray Smith
* Created: Thu Sep 25 17:12:01 PDT 2008
*
* (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.
*
**********************************************************************/
#ifdef _WIN32
#ifndef __GNUC__
#include <windows.h>
#endif // __GNUC__
#ifndef unlink
#include <io.h>
#endif
#else
#include <unistd.h>
#endif // _WIN32
#ifdef _MSC_VER
#pragma warning(disable:4244) // Conversion warnings
#endif
// Include automatically generated configuration file if running autoconf.
#ifdef HAVE_CONFIG_H
#include "config_auto.h"
#endif
#include "allheaders.h"
#include "blobbox.h"
#include "blread.h"
#include "colfind.h"
#include "equationdetect.h"
#include "imagefind.h"
#include "linefind.h"
#include "makerow.h"
#include "osdetect.h"
#include "tabvector.h"
#include "tesseractclass.h"
#include "tessvars.h"
#include "textord.h"
#include "tordmain.h"
#include "wordseg.h"
namespace tesseract {
/// Minimum believable resolution.
const int kMinCredibleResolution = 70;
/// Default resolution used if input in not believable.
const int kDefaultResolution = 300;
// Max erosions to perform in removing an enclosing circle.
const int kMaxCircleErosions = 8;
// Helper to remove an enclosing circle from an image.
// If there isn't one, then the image will most likely get badly mangled.
// The returned pix must be pixDestroyed after use. NULL may be returned
// if the image doesn't meet the trivial conditions that it uses to determine
// success.
static Pix* RemoveEnclosingCircle(Pix* pixs) {
Pix* pixsi = pixInvert(NULL, pixs);
Pix* pixc = pixCreateTemplate(pixs);
pixSetOrClearBorder(pixc, 1, 1, 1, 1, PIX_SET);
pixSeedfillBinary(pixc, pixc, pixsi, 4);
pixInvert(pixc, pixc);
pixDestroy(&pixsi);
Pix* pixt = pixAnd(NULL, pixs, pixc);
l_int32 max_count;
pixCountConnComp(pixt, 8, &max_count);
// The count has to go up before we start looking for the minimum.
l_int32 min_count = MAX_INT32;
Pix* pixout = NULL;
for (int i = 1; i < kMaxCircleErosions; i++) {
pixDestroy(&pixt);
pixErodeBrick(pixc, pixc, 3, 3);
pixt = pixAnd(NULL, pixs, pixc);
l_int32 count;
pixCountConnComp(pixt, 8, &count);
if (i == 1 || count > max_count) {
max_count = count;
min_count = count;
} else if (i > 1 && count < min_count) {
min_count = count;
pixDestroy(&pixout);
pixout = pixCopy(NULL, pixt); // Save the best.
} else if (count >= min_count) {
break; // We have passed by the best.
}
}
pixDestroy(&pixt);
pixDestroy(&pixc);
return pixout;
}
/**
* Segment the page according to the current value of tessedit_pageseg_mode.
* pix_binary_ is used as the source image and should not be NULL.
* On return the blocks list owns all the constructed page layout.
*/
int Tesseract::SegmentPage(const STRING* input_file, BLOCK_LIST* blocks,
Tesseract* osd_tess, OSResults* osr) {
ASSERT_HOST(pix_binary_ != NULL);
int width = pixGetWidth(pix_binary_);
int height = pixGetHeight(pix_binary_);
// Get page segmentation mode.
PageSegMode pageseg_mode = static_cast<PageSegMode>(
static_cast<int>(tessedit_pageseg_mode));
// If a UNLV zone file can be found, use that instead of segmentation.
if (!PSM_COL_FIND_ENABLED(pageseg_mode) &&
input_file != NULL && input_file->length() > 0) {
STRING name = *input_file;
const char* lastdot = strrchr(name.string(), '.');
if (lastdot != NULL)
name[lastdot - name.string()] = '\0';
read_unlv_file(name, width, height, blocks);
}
if (blocks->empty()) {
// No UNLV file present. Work according to the PageSegMode.
// First make a single block covering the whole image.
BLOCK_IT block_it(blocks);
BLOCK* block = new BLOCK("", TRUE, 0, 0, 0, 0, width, height);
block->set_right_to_left(right_to_left());
block_it.add_to_end(block);
} else {
// UNLV file present. Use PSM_SINGLE_BLOCK.
pageseg_mode = PSM_SINGLE_BLOCK;
}
// The diacritic_blobs holds noise blobs that may be diacritics. They
// are separated out on areas of the image that seem noisy and short-circuit
// the layout process, going straight from the initial partition creation
// right through to after word segmentation, where they are added to the
// rej_cblobs list of the most appropriate word. From there classification
// will determine whether they are used.
BLOBNBOX_LIST diacritic_blobs;
int auto_page_seg_ret_val = 0;
TO_BLOCK_LIST to_blocks;
if (PSM_OSD_ENABLED(pageseg_mode) || PSM_BLOCK_FIND_ENABLED(pageseg_mode) ||
PSM_SPARSE(pageseg_mode)) {
auto_page_seg_ret_val = AutoPageSeg(
pageseg_mode, blocks, &to_blocks,
enable_noise_removal ? &diacritic_blobs : NULL, osd_tess, osr);
if (pageseg_mode == PSM_OSD_ONLY)
return auto_page_seg_ret_val;
// To create blobs from the image region bounds uncomment this line:
// to_blocks.clear(); // Uncomment to go back to the old mode.
} else {
deskew_ = FCOORD(1.0f, 0.0f);
reskew_ = FCOORD(1.0f, 0.0f);
if (pageseg_mode == PSM_CIRCLE_WORD) {
Pix* pixcleaned = RemoveEnclosingCircle(pix_binary_);
if (pixcleaned != NULL) {
pixDestroy(&pix_binary_);
pix_binary_ = pixcleaned;
}
}
}
if (auto_page_seg_ret_val < 0) {
return -1;
}
if (blocks->empty()) {
if (textord_debug_tabfind)
tprintf("Empty page\n");
return 0; // AutoPageSeg found an empty page.
}
bool splitting =
pageseg_devanagari_split_strategy != ShiroRekhaSplitter::NO_SPLIT;
bool cjk_mode = textord_use_cjk_fp_model;
textord_.TextordPage(pageseg_mode, reskew_, width, height, pix_binary_,
pix_thresholds_, pix_grey_, splitting || cjk_mode,
&diacritic_blobs, blocks, &to_blocks);
return auto_page_seg_ret_val;
}
// Helper writes a grey image to a file for use by scrollviewer.
// Normally for speed we don't display the image in the layout debug windows.
// If textord_debug_images is true, we draw the image as a background to some
// of the debug windows. printable determines whether these
// images are optimized for printing instead of screen display.
static void WriteDebugBackgroundImage(bool printable, Pix* pix_binary) {
Pix* grey_pix = pixCreate(pixGetWidth(pix_binary),
pixGetHeight(pix_binary), 8);
// Printable images are light grey on white, but for screen display
// they are black on dark grey so the other colors show up well.
if (printable) {
pixSetAll(grey_pix);
pixSetMasked(grey_pix, pix_binary, 192);
} else {
pixSetAllArbitrary(grey_pix, 64);
pixSetMasked(grey_pix, pix_binary, 0);
}
AlignedBlob::IncrementDebugPix();
pixWrite(AlignedBlob::textord_debug_pix().string(), grey_pix, IFF_PNG);
pixDestroy(&grey_pix);
}
/**
* Auto page segmentation. Divide the page image into blocks of uniform
* text linespacing and images.
*
* Resolution (in ppi) is derived from the input image.
*
* The output goes in the blocks list with corresponding TO_BLOCKs in the
* to_blocks list.
*
* If !PSM_COL_FIND_ENABLED(pageseg_mode), then no attempt is made to divide
* the image into columns, but multiple blocks are still made if the text is
* of non-uniform linespacing.
*
* If diacritic_blobs is non-null, then diacritics/noise blobs, that would
* confuse layout anaylsis by causing textline overlap, are placed there,
* with the expectation that they will be reassigned to words later and
* noise/diacriticness determined via classification.
*
* If osd (orientation and script detection) is true then that is performed
* as well. If only_osd is true, then only orientation and script detection is
* performed. If osd is desired, (osd or only_osd) then osr_tess must be
* another Tesseract that was initialized especially for osd, and the results
* will be output into osr (orientation and script result).
*/
int Tesseract::AutoPageSeg(PageSegMode pageseg_mode, BLOCK_LIST* blocks,
TO_BLOCK_LIST* to_blocks,
BLOBNBOX_LIST* diacritic_blobs, Tesseract* osd_tess,
OSResults* osr) {
if (textord_debug_images) {
WriteDebugBackgroundImage(textord_debug_printable, pix_binary_);
}
Pix* photomask_pix = NULL;
Pix* musicmask_pix = NULL;
// The blocks made by the ColumnFinder. Moved to blocks before return.
BLOCK_LIST found_blocks;
TO_BLOCK_LIST temp_blocks;
ColumnFinder* finder = SetupPageSegAndDetectOrientation(
pageseg_mode, blocks, osd_tess, osr, &temp_blocks, &photomask_pix,
&musicmask_pix);
int result = 0;
if (finder != NULL) {
TO_BLOCK_IT to_block_it(&temp_blocks);
TO_BLOCK* to_block = to_block_it.data();
if (musicmask_pix != NULL) {
// TODO(rays) pass the musicmask_pix into FindBlocks and mark music
// blocks separately. For now combine with photomask_pix.
pixOr(photomask_pix, photomask_pix, musicmask_pix);
}
if (equ_detect_) {
finder->SetEquationDetect(equ_detect_);
}
result = finder->FindBlocks(
pageseg_mode, scaled_color_, scaled_factor_, to_block, photomask_pix,
pix_thresholds_, pix_grey_, &found_blocks, diacritic_blobs, to_blocks);
if (result >= 0)
finder->GetDeskewVectors(&deskew_, &reskew_);
delete finder;
}
pixDestroy(&photomask_pix);
pixDestroy(&musicmask_pix);
if (result < 0) return result;
blocks->clear();
BLOCK_IT block_it(blocks);
// Move the found blocks to the input/output blocks.
block_it.add_list_after(&found_blocks);
if (textord_debug_images) {
// The debug image is no longer needed so delete it.
unlink(AlignedBlob::textord_debug_pix().string());
}
return result;
}
// Helper adds all the scripts from sid_set converted to ids from osd_set to
// allowed_ids.
static void AddAllScriptsConverted(const UNICHARSET& sid_set,
const UNICHARSET& osd_set,
GenericVector<int>* allowed_ids) {
for (int i = 0; i < sid_set.get_script_table_size(); ++i) {
if (i != sid_set.null_sid()) {
const char* script = sid_set.get_script_from_script_id(i);
allowed_ids->push_back(osd_set.get_script_id_from_name(script));
}
}
}
/**
* Sets up auto page segmentation, determines the orientation, and corrects it.
* Somewhat arbitrary chunk of functionality, factored out of AutoPageSeg to
* facilitate testing.
* photo_mask_pix is a pointer to a NULL pointer that will be filled on return
* with the leptonica photo mask, which must be pixDestroyed by the caller.
* to_blocks is an empty list that will be filled with (usually a single)
* block that is used during layout analysis. This ugly API is required
* because of the possibility of a unlv zone file.
* TODO(rays) clean this up.
* See AutoPageSeg for other arguments.
* The returned ColumnFinder must be deleted after use.
*/
ColumnFinder* Tesseract::SetupPageSegAndDetectOrientation(
PageSegMode pageseg_mode, BLOCK_LIST* blocks, Tesseract* osd_tess,
OSResults* osr, TO_BLOCK_LIST* to_blocks, Pix** photo_mask_pix,
Pix** music_mask_pix) {
int vertical_x = 0;
int vertical_y = 1;
TabVector_LIST v_lines;
TabVector_LIST h_lines;
ICOORD bleft(0, 0);
ASSERT_HOST(pix_binary_ != NULL);
if (tessedit_dump_pageseg_images) {
pixWrite("tessinput.png", pix_binary_, IFF_PNG);
}
// Leptonica is used to find the rule/separator lines in the input.
LineFinder::FindAndRemoveLines(source_resolution_,
textord_tabfind_show_vlines, pix_binary_,
&vertical_x, &vertical_y, music_mask_pix,
&v_lines, &h_lines);
if (tessedit_dump_pageseg_images)
pixWrite("tessnolines.png", pix_binary_, IFF_PNG);
// Leptonica is used to find a mask of the photo regions in the input.
*photo_mask_pix = ImageFind::FindImages(pix_binary_);
if (tessedit_dump_pageseg_images)
pixWrite("tessnoimages.png", pix_binary_, IFF_PNG);
if (!PSM_COL_FIND_ENABLED(pageseg_mode)) v_lines.clear();
// The rest of the algorithm uses the usual connected components.
textord_.find_components(pix_binary_, blocks, to_blocks);
TO_BLOCK_IT to_block_it(to_blocks);
// There must be exactly one input block.
// TODO(rays) handle new textline finding with a UNLV zone file.
ASSERT_HOST(to_blocks->singleton());
TO_BLOCK* to_block = to_block_it.data();
TBOX blkbox = to_block->block->bounding_box();
ColumnFinder* finder = NULL;
if (to_block->line_size >= 2) {
finder = new ColumnFinder(static_cast<int>(to_block->line_size),
blkbox.botleft(), blkbox.topright(),
source_resolution_, textord_use_cjk_fp_model,
textord_tabfind_aligned_gap_fraction,
&v_lines, &h_lines, vertical_x, vertical_y);
finder->SetupAndFilterNoise(pageseg_mode, *photo_mask_pix, to_block);
if (equ_detect_) {
equ_detect_->LabelSpecialText(to_block);
}
BLOBNBOX_CLIST osd_blobs;
// osd_orientation is the number of 90 degree rotations to make the
// characters upright. (See osdetect.h for precise definition.)
// We want the text lines horizontal, (vertical text indicates vertical
// textlines) which may conflict (eg vertically written CJK).
int osd_orientation = 0;
bool vertical_text = textord_tabfind_force_vertical_text ||
pageseg_mode == PSM_SINGLE_BLOCK_VERT_TEXT;
if (!vertical_text && textord_tabfind_vertical_text &&
PSM_ORIENTATION_ENABLED(pageseg_mode)) {
vertical_text =
finder->IsVerticallyAlignedText(textord_tabfind_vertical_text_ratio,
to_block, &osd_blobs);
}
if (PSM_OSD_ENABLED(pageseg_mode) && osd_tess != NULL && osr != NULL) {
GenericVector<int> osd_scripts;
if (osd_tess != this) {
// We are running osd as part of layout analysis, so constrain the
// scripts to those allowed by *this.
AddAllScriptsConverted(unicharset, osd_tess->unicharset, &osd_scripts);
for (int s = 0; s < sub_langs_.size(); ++s) {
AddAllScriptsConverted(sub_langs_[s]->unicharset,
osd_tess->unicharset, &osd_scripts);
}
}
os_detect_blobs(&osd_scripts, &osd_blobs, osr, osd_tess);
if (pageseg_mode == PSM_OSD_ONLY) {
delete finder;
return NULL;
}
osd_orientation = osr->best_result.orientation_id;
double osd_score = osr->orientations[osd_orientation];
double osd_margin = min_orientation_margin * 2;
for (int i = 0; i < 4; ++i) {
if (i != osd_orientation &&
osd_score - osr->orientations[i] < osd_margin) {
osd_margin = osd_score - osr->orientations[i];
}
}
int best_script_id = osr->best_result.script_id;
const char* best_script_str =
osd_tess->unicharset.get_script_from_script_id(best_script_id);
bool cjk = best_script_id == osd_tess->unicharset.han_sid() ||
best_script_id == osd_tess->unicharset.hiragana_sid() ||
best_script_id == osd_tess->unicharset.katakana_sid() ||
strcmp("Japanese", best_script_str) == 0 ||
strcmp("Korean", best_script_str) == 0 ||
strcmp("Hangul", best_script_str) == 0;
if (cjk) {
finder->set_cjk_script(true);
}
if (osd_margin < min_orientation_margin) {
// The margin is weak.
if (!cjk && !vertical_text && osd_orientation == 2) {
// upside down latin text is improbable with such a weak margin.
tprintf("OSD: Weak margin (%.2f), horiz textlines, not CJK: "
"Don't rotate.\n", osd_margin);
osd_orientation = 0;
} else {
tprintf("OSD: Weak margin (%.2f) for %d blob text block, "
"but using orientation anyway: %d\n",
osd_blobs.length(), osd_margin, osd_orientation);
}
}
}
osd_blobs.shallow_clear();
finder->CorrectOrientation(to_block, vertical_text, osd_orientation);
}
return finder;
}
} // namespace tesseract.
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