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fix issue tesseract-ocr#1192
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@theraysmith @zdenop
theraysmith authored and zdenop committed Nov 12, 2018
1 parent 7249571 commit ce88adb
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Showing 2 changed files with 91 additions and 38 deletions.
125 changes: 87 additions & 38 deletions src/ccstruct/pageres.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1292,7 +1292,8 @@ WERD_RES* PAGE_RES_IT::InsertSimpleCloneWord(const WERD_RES& clone_res,
// Helper computes the boundaries between blobs in the word. The blob bounds
// are likely very poor, if they come from LSTM, where it only outputs the
// character at one pixel within it, so we find the midpoints between them.
static void ComputeBlobEnds(const WERD_RES& word, C_BLOB_LIST* next_word_blobs,
static void ComputeBlobEnds(const WERD_RES& word, const TBOX& clip_box,
C_BLOB_LIST* next_word_blobs,
GenericVector<int>* blob_ends) {
C_BLOB_IT blob_it(word.word->cblob_list());
for (int i = 0; i < word.best_state.size(); ++i) {
Expand All @@ -1312,8 +1313,74 @@ static void ComputeBlobEnds(const WERD_RES& word, C_BLOB_LIST* next_word_blobs,
blob_it.set_to_list(next_word_blobs);
blob_end = (blob_box.right() + blob_it.data()->bounding_box().left()) / 2;
}
blob_end = ClipToRange<int>(blob_end, clip_box.left(), clip_box.right());
blob_ends->push_back(blob_end);
}
blob_ends->back() = clip_box.right();
}

// Helper computes the bounds of a word by restricting it to existing words
// that significantly overlap.
static TBOX ComputeWordBounds(const tesseract::PointerVector<WERD_RES>& words,
int w_index, TBOX prev_box, WERD_RES_IT w_it) {
constexpr int kSignificantOverlapFraction = 4;
TBOX clipped_box;
TBOX current_box = words[w_index]->word->bounding_box();
TBOX next_box;
if (w_index + 1 < words.size() && words[w_index + 1] != nullptr &&
words[w_index + 1]->word != nullptr)
next_box = words[w_index + 1]->word->bounding_box();
for (w_it.forward(); !w_it.at_first() && w_it.data()->part_of_combo;
w_it.forward()) {
if (w_it.data() == nullptr || w_it.data()->word == nullptr) continue;
TBOX w_box = w_it.data()->word->bounding_box();
int height_limit = std::min<int>(w_box.height(), w_box.width() / 2);
int width_limit = w_box.width() / kSignificantOverlapFraction;
int min_significant_overlap = std::max(height_limit, width_limit);
int overlap = w_box.intersection(current_box).width();
int prev_overlap = w_box.intersection(prev_box).width();
int next_overlap = w_box.intersection(next_box).width();
if (overlap > min_significant_overlap) {
if (prev_overlap > min_significant_overlap) {
// We have no choice but to use the LSTM word edge.
clipped_box.set_left(current_box.left());
} else if (next_overlap > min_significant_overlap) {
// We have no choice but to use the LSTM word edge.
clipped_box.set_right(current_box.right());
} else {
clipped_box += w_box;
}
}
}
if (clipped_box.height() <= 0) {
clipped_box.set_top(current_box.top());
clipped_box.set_bottom(current_box.bottom());
}
if (clipped_box.width() <= 0) clipped_box = current_box;
return clipped_box;
}

// Helper moves the blob from src to dest. If it isn't contained by clip_box,
// the blob is replaced by a fake that is contained.
static TBOX MoveAndClipBlob(C_BLOB_IT* src_it, C_BLOB_IT* dest_it,
const TBOX& clip_box) {
C_BLOB* src_blob = src_it->extract();
TBOX box = src_blob->bounding_box();
if (!clip_box.contains(box)) {
int left =
ClipToRange<int>(box.left(), clip_box.left(), clip_box.right() - 1);
int right =
ClipToRange<int>(box.right(), clip_box.left() + 1, clip_box.right());
int top =
ClipToRange<int>(box.top(), clip_box.bottom() + 1, clip_box.top());
int bottom =
ClipToRange<int>(box.bottom(), clip_box.bottom(), clip_box.top() - 1);
box = TBOX(left, bottom, right, top);
delete src_blob;
src_blob = C_BLOB::FakeBlob(box);
}
dest_it->add_after_then_move(src_blob);
return box;
}

// Replaces the current WERD/WERD_RES with the given words. The given words
Expand Down Expand Up @@ -1364,65 +1431,44 @@ void PAGE_RES_IT::ReplaceCurrentWord(
src_b_it.sort(&C_BLOB::SortByXMiddle);
C_BLOB_IT rej_b_it(input_word->word->rej_cblob_list());
rej_b_it.sort(&C_BLOB::SortByXMiddle);
TBOX clip_box;
for (int w = 0; w < words->size(); ++w) {
WERD_RES* word_w = (*words)[w];
clip_box = ComputeWordBounds(*words, w, clip_box, wr_it_of_current_word);
// Compute blob boundaries.
GenericVector<int> blob_ends;
C_BLOB_LIST* next_word_blobs =
w + 1 < words->size() ? (*words)[w + 1]->word->cblob_list() : nullptr;
ComputeBlobEnds(*word_w, next_word_blobs, &blob_ends);
// Delete the fake blobs on the current word.
ComputeBlobEnds(*word_w, clip_box, next_word_blobs, &blob_ends);
// Remove the fake blobs on the current word, but keep safe for back-up if
// no blob can be found.
C_BLOB_LIST fake_blobs;
C_BLOB_IT fake_b_it(&fake_blobs);
fake_b_it.add_list_after(word_w->word->cblob_list());
fake_b_it.move_to_first();
word_w->word->cblob_list()->clear();
C_BLOB_IT dest_it(word_w->word->cblob_list());
// Build the box word as we move the blobs.
tesseract::BoxWord* box_word = new tesseract::BoxWord;
for (int i = 0; i < blob_ends.size(); ++i) {
for (int i = 0; i < blob_ends.size(); ++i, fake_b_it.forward()) {
int end_x = blob_ends[i];
TBOX blob_box;
// Add the blobs up to end_x.
while (!src_b_it.empty() &&
src_b_it.data()->bounding_box().x_middle() < end_x) {
blob_box += src_b_it.data()->bounding_box();
dest_it.add_after_then_move(src_b_it.extract());
blob_box += MoveAndClipBlob(&src_b_it, &dest_it, clip_box);
src_b_it.forward();
}
while (!rej_b_it.empty() &&
rej_b_it.data()->bounding_box().x_middle() < end_x) {
blob_box += rej_b_it.data()->bounding_box();
dest_it.add_after_then_move(rej_b_it.extract());
blob_box += MoveAndClipBlob(&rej_b_it, &dest_it, clip_box);
rej_b_it.forward();
}
// Clip to the previously computed bounds. Although imperfectly accurate,
// it is good enough, and much more complicated to determine where else
// to clip.
if (i > 0 && blob_box.left() < blob_ends[i - 1])
blob_box.set_left(blob_ends[i - 1]);
if (blob_box.right() > end_x)
blob_box.set_right(end_x);
box_word->InsertBox(i, blob_box);
}
// Fix empty boxes. If a very joined blob sits over multiple characters,
// then we will have some empty boxes from using the middle, so look for
// overlaps.
for (int i = 0; i < box_word->length(); ++i) {
TBOX box = box_word->BlobBox(i);
if (box.null_box()) {
// Nothing has its middle in the bounds of this blob, so use anything
// that overlaps.
for (dest_it.mark_cycle_pt(); !dest_it.cycled_list();
dest_it.forward()) {
TBOX blob_box = dest_it.data()->bounding_box();
if (blob_box.left() < blob_ends[i] &&
(i == 0 || blob_box.right() >= blob_ends[i - 1])) {
if (i > 0 && blob_box.left() < blob_ends[i - 1])
blob_box.set_left(blob_ends[i - 1]);
if (blob_box.right() > blob_ends[i])
blob_box.set_right(blob_ends[i]);
box_word->ChangeBox(i, blob_box);
break;
}
}
if (blob_box.null_box()) {
// Use the original box as a back-up.
blob_box = MoveAndClipBlob(&fake_b_it, &dest_it, clip_box);
}
box_word->InsertBox(i, blob_box);
}
delete word_w->box_word;
word_w->box_word = box_word;
Expand Down Expand Up @@ -1544,6 +1590,7 @@ void PAGE_RES_IT::ResetWordIterator() {
}
}
ASSERT_HOST(!word_res_it.cycled_list());
wr_it_of_next_word = word_res_it;
word_res_it.forward();
} else {
// word_res_it is OK, but reset word_res and prev_word_res if needed.
Expand Down Expand Up @@ -1581,6 +1628,7 @@ WERD_RES *PAGE_RES_IT::internal_forward(bool new_block, bool empty_ok) {
block_res = next_block_res;
row_res = next_row_res;
word_res = next_word_res;
wr_it_of_current_word = wr_it_of_next_word;
next_block_res = nullptr;
next_row_res = nullptr;
next_word_res = nullptr;
Expand Down Expand Up @@ -1609,6 +1657,7 @@ WERD_RES *PAGE_RES_IT::internal_forward(bool new_block, bool empty_ok) {
next_block_res = block_res_it.data();
next_row_res = row_res_it.data();
next_word_res = word_res_it.data();
wr_it_of_next_word = word_res_it;
word_res_it.forward();
goto foundword;
}
Expand Down
4 changes: 4 additions & 0 deletions src/ccstruct/pageres.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -787,5 +787,9 @@ class PAGE_RES_IT {
BLOCK_RES_IT block_res_it; // iterators
ROW_RES_IT row_res_it;
WERD_RES_IT word_res_it;
// Iterators used to get the state of word_res_it for the current word.
// Since word_res_it is 2 words further on, this is otherwise hard to do.
WERD_RES_IT wr_it_of_current_word;
WERD_RES_IT wr_it_of_next_word;
};
#endif

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