mirror of
https://github.com/tesseract-ocr/tesseract.git
synced 2024-12-13 07:59:04 +08:00
175 lines
6.9 KiB
C++
175 lines
6.9 KiB
C++
///////////////////////////////////////////////////////////////////////
|
|
// File: associate.cpp
|
|
// Description: Functions for scoring segmentation paths according to
|
|
// their character widths, gap widths and seam cuts.
|
|
// Author: Daria Antonova
|
|
// Created: Mon Mar 8 11:26:43 PDT 2010
|
|
//
|
|
// (C) Copyright 2010, 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.
|
|
//
|
|
///////////////////////////////////////////////////////////////////////
|
|
|
|
|
|
#include <stdio.h>
|
|
#ifdef __UNIX__
|
|
#include <assert.h>
|
|
#endif
|
|
#include <math.h>
|
|
|
|
#include "associate.h"
|
|
#include "normalis.h"
|
|
#include "pageres.h"
|
|
|
|
namespace tesseract {
|
|
|
|
const float AssociateUtils::kMaxFixedPitchCharAspectRatio = 2.0f;
|
|
const float AssociateUtils::kMinGap = 0.03f;
|
|
|
|
void AssociateUtils::ComputeStats(int col, int row,
|
|
const AssociateStats *parent_stats,
|
|
int parent_path_length,
|
|
bool fixed_pitch,
|
|
float max_char_wh_ratio,
|
|
WERD_RES *word_res,
|
|
bool debug,
|
|
AssociateStats *stats) {
|
|
stats->Clear();
|
|
|
|
ASSERT_HOST(word_res != NULL);
|
|
if (word_res->blob_widths.empty()) {
|
|
return;
|
|
}
|
|
if (debug) {
|
|
tprintf("AssociateUtils::ComputeStats() for col=%d, row=%d%s\n",
|
|
col, row, fixed_pitch ? " (fixed pitch)" : "");
|
|
}
|
|
float normalizing_height = kBlnXHeight;
|
|
ROW* blob_row = word_res->blob_row;
|
|
// TODO(rays/daria) Can unicharset.script_has_xheight be useful here?
|
|
if (fixed_pitch && blob_row != NULL) {
|
|
// For fixed pitch language like CJK, we use the full text height
|
|
// as the normalizing factor so we are not dependent on xheight
|
|
// calculation.
|
|
if (blob_row->body_size() > 0.0f) {
|
|
normalizing_height = word_res->denorm.y_scale() * blob_row->body_size();
|
|
} else {
|
|
normalizing_height = word_res->denorm.y_scale() *
|
|
(blob_row->x_height() + blob_row->ascenders());
|
|
}
|
|
if (debug) {
|
|
tprintf("normalizing height = %g (scale %g xheight %g ascenders %g)\n",
|
|
normalizing_height, word_res->denorm.y_scale(),
|
|
blob_row->x_height(), blob_row->ascenders());
|
|
}
|
|
}
|
|
float wh_ratio = word_res->GetBlobsWidth(col, row) / normalizing_height;
|
|
if (wh_ratio > max_char_wh_ratio) stats->bad_shape = true;
|
|
// Compute the gap sum for this shape. If there are only negative or only
|
|
// positive gaps, record their sum in stats->gap_sum. However, if there is
|
|
// a mixture, record only the sum of the positive gaps.
|
|
// TODO(antonova): explain fragment.
|
|
int negative_gap_sum = 0;
|
|
for (int c = col; c < row; ++c) {
|
|
int gap = word_res->GetBlobsGap(c);
|
|
(gap > 0) ? stats->gap_sum += gap : negative_gap_sum += gap;
|
|
}
|
|
if (stats->gap_sum == 0) stats->gap_sum = negative_gap_sum;
|
|
if (debug) {
|
|
tprintf("wh_ratio=%g (max_char_wh_ratio=%g) gap_sum=%d %s\n",
|
|
wh_ratio, max_char_wh_ratio, stats->gap_sum,
|
|
stats->bad_shape ? "bad_shape" : "");
|
|
}
|
|
// Compute shape_cost (for fixed pitch mode).
|
|
if (fixed_pitch) {
|
|
bool end_row = (row == (word_res->ratings->dimension() - 1));
|
|
|
|
// Ensure that the blob has gaps on the left and the right sides
|
|
// (except for beginning and ending punctuation) and that there is
|
|
// no cutting through ink at the blob boundaries.
|
|
if (col > 0) {
|
|
float left_gap = word_res->GetBlobsGap(col - 1) / normalizing_height;
|
|
SEAM *left_seam = word_res->seam_array[col - 1];
|
|
if ((!end_row && left_gap < kMinGap) || left_seam->priority() > 0.0f) {
|
|
stats->bad_shape = true;
|
|
}
|
|
if (debug) {
|
|
tprintf("left_gap %g, left_seam %g %s\n", left_gap,
|
|
left_seam->priority(), stats->bad_shape ? "bad_shape" : "");
|
|
}
|
|
}
|
|
float right_gap = 0.0f;
|
|
if (!end_row) {
|
|
right_gap = word_res->GetBlobsGap(row) / normalizing_height;
|
|
SEAM *right_seam = word_res->seam_array[row];
|
|
if (right_gap < kMinGap || right_seam->priority() > 0.0f) {
|
|
stats->bad_shape = true;
|
|
if (right_gap < kMinGap) stats->bad_fixed_pitch_right_gap = true;
|
|
}
|
|
if (debug) {
|
|
tprintf("right_gap %g right_seam %g %s\n", right_gap,
|
|
right_seam->priority(), stats->bad_shape ? "bad_shape" : "");
|
|
}
|
|
}
|
|
|
|
// Impose additional segmentation penalties if blob widths or gaps
|
|
// distribution don't fit a fixed-pitch model.
|
|
// Since we only know the widths and gaps of the path explored so far,
|
|
// the means and variances are computed for the path so far (not
|
|
// considering characters to the right of the last character on the path).
|
|
stats->full_wh_ratio = wh_ratio + right_gap;
|
|
if (parent_stats != NULL) {
|
|
stats->full_wh_ratio_total =
|
|
(parent_stats->full_wh_ratio_total + stats->full_wh_ratio);
|
|
float mean =
|
|
stats->full_wh_ratio_total / static_cast<float>(parent_path_length+1);
|
|
stats->full_wh_ratio_var =
|
|
parent_stats->full_wh_ratio_var + pow(mean-stats->full_wh_ratio, 2);
|
|
} else {
|
|
stats->full_wh_ratio_total = stats->full_wh_ratio;
|
|
}
|
|
if (debug) {
|
|
tprintf("full_wh_ratio %g full_wh_ratio_total %g full_wh_ratio_var %g\n",
|
|
stats->full_wh_ratio, stats->full_wh_ratio_total,
|
|
stats->full_wh_ratio_var);
|
|
}
|
|
|
|
stats->shape_cost =
|
|
FixedPitchWidthCost(wh_ratio, right_gap, end_row, max_char_wh_ratio);
|
|
|
|
// For some reason Tesseract prefers to treat the whole CJ words
|
|
// as one blob when the initial segmentation is particularly bad.
|
|
// This hack is to avoid favoring such states.
|
|
if (col == 0 && end_row && wh_ratio > max_char_wh_ratio) {
|
|
stats->shape_cost += 10;
|
|
}
|
|
stats->shape_cost += stats->full_wh_ratio_var;
|
|
if (debug) tprintf("shape_cost %g\n", stats->shape_cost);
|
|
}
|
|
}
|
|
|
|
float AssociateUtils::FixedPitchWidthCost(float norm_width,
|
|
float right_gap,
|
|
bool end_pos,
|
|
float max_char_wh_ratio) {
|
|
float cost = 0.0f;
|
|
if (norm_width > max_char_wh_ratio) cost += norm_width;
|
|
if (norm_width > kMaxFixedPitchCharAspectRatio)
|
|
cost += norm_width * norm_width; // extra penalty for merging CJK chars
|
|
// Penalize skinny blobs, except for punctuation in the last position.
|
|
if (norm_width+right_gap < 0.5f && !end_pos) {
|
|
cost += 1.0f - (norm_width + right_gap);
|
|
}
|
|
return cost;
|
|
}
|
|
|
|
} // namespace tesseract
|