// Computes the noise_density_ by summing the number of elements in a
// neighbourhood of each grid cell.
void StrokeWidth::ComputeNoiseDensity(TO_BLOCK* block, TabFind* line_grid) {
// Run a preliminary strokewidth neighbour detection on the medium blobs.
line_grid->InsertBlobList(true, true, false, &block->blobs, false, this);
BLOBNBOX_IT blob_it(&block->blobs);
for (blob_it.mark_cycle_pt(); !blob_it.cycled_list(); blob_it.forward()) {
SetNeighbours(false, blob_it.data());
}
// Remove blobs with a good strokewidth neighbour from the grid.
for (blob_it.mark_cycle_pt(); !blob_it.cycled_list(); blob_it.forward()) {
BLOBNBOX* blob = blob_it.data();
if (blob->GoodTextBlob() > 0)
RemoveBBox(blob);
blob->ClearNeighbours();
}
// Insert the smaller blobs into the grid.
line_grid->InsertBlobList(true, true, false, &block->small_blobs,
false, this);
line_grid->InsertBlobList(true, true, false, &block->noise_blobs,
false, this);
if (noise_density_ != NULL)
delete noise_density_;
IntGrid* cell_counts = CountCellElements();
noise_density_ = cell_counts->NeighbourhoodSum();
delete cell_counts;
// Clear the grid as we don't want the small stuff hanging around in it.
Clear();
}
// Tests each blob in the list to see if it is certain non-text using 2
// conditions:
// 1. blob overlaps a cell with high value in noise_density_ (previously set
// by ComputeNoiseDensity).
// OR 2. The blob overlaps more than max_blob_overlaps in *this grid. This
// condition is disabled with max_blob_overlaps == -1.
// If it does, the blob is declared non-text, and is used to mark up the
// nontext_mask. Such blobs are fully deleted, and non-noise blobs have their
// neighbours reset, as they may now point to deleted data.
// WARNING: The blobs list blobs may be in the *this grid, but they are
// not removed. If any deleted blobs might be in *this, then this must be
// Clear()ed immediately after MarkAndDeleteNonTextBlobs is called.
// If the win is not NULL, deleted blobs are drawn on it in red, and kept
// blobs are drawn on it in ok_color.
void CCNonTextDetect::MarkAndDeleteNonTextBlobs(BLOBNBOX_LIST* blobs,
int max_blob_overlaps,
ScrollView* win,
ScrollView::Color ok_color,
Pix* nontext_mask) {
int imageheight = tright().y() - bleft().x();
BLOBNBOX_IT blob_it(blobs);
BLOBNBOX_LIST dead_blobs;
BLOBNBOX_IT dead_it(&dead_blobs);
for (blob_it.mark_cycle_pt(); !blob_it.cycled_list(); blob_it.forward()) {
BLOBNBOX* blob = blob_it.data();
TBOX box = blob->bounding_box();
if (!noise_density_->RectMostlyOverThreshold(box, max_noise_count_) &&
(max_blob_overlaps < 0 ||
!BlobOverlapsTooMuch(blob, max_blob_overlaps))) {
blob->ClearNeighbours();
#ifndef GRAPHICS_DISABLED
if (win != NULL)
blob->plot(win, ok_color, ok_color);
#endif // GRAPHICS_DISABLED
} else {
if (noise_density_->AnyZeroInRect(box)) {
// There is a danger that the bounding box may overlap real text, so
// we need to render the outline.
Pix* blob_pix = blob->cblob()->render_outline();
pixRasterop(nontext_mask, box.left(), imageheight - box.top(),
box.width(), box.height(), PIX_SRC | PIX_DST,
blob_pix, 0, 0);
pixDestroy(&blob_pix);
} else {
if (box.area() < gridsize() * gridsize()) {
// It is a really bad idea to make lots of small components in the
// photo mask, so try to join it to a bigger area by expanding the
// box in a way that does not touch any zero noise density cell.
box = AttemptBoxExpansion(box, *noise_density_, gridsize());
}
// All overlapped cells are non-zero, so just mark the rectangle.
pixRasterop(nontext_mask, box.left(), imageheight - box.top(),
box.width(), box.height(), PIX_SET, NULL, 0, 0);
}
#ifndef GRAPHICS_DISABLED
if (win != NULL)
blob->plot(win, ScrollView::RED, ScrollView::RED);
#endif // GRAPHICS_DISABLED
// It is safe to delete the cblob now, as it isn't used by the grid
// or BlobOverlapsTooMuch, and the BLOBNBOXes will go away with the
// dead_blobs list.
// TODO(rays) delete the delete when the BLOBNBOX destructor deletes
// the cblob.
delete blob->cblob();
dead_it.add_to_end(blob_it.extract());
}
}
}
// Moves blobs that look like they don't sit well on a textline from the
// input blobs list to the output small_blobs list.
// This gets them away from initial textline finding to stop diacritics
// from forming incorrect textlines. (Introduced mainly to fix Thai.)
void TextlineProjection::MoveNonTextlineBlobs(
BLOBNBOX_LIST* blobs, BLOBNBOX_LIST* small_blobs) const {
BLOBNBOX_IT it(blobs);
BLOBNBOX_IT small_it(small_blobs);
for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
BLOBNBOX* blob = it.data();
const TBOX& box = blob->bounding_box();
bool debug = AlignedBlob::WithinTestRegion(2, box.left(),
box.bottom());
if (BoxOutOfHTextline(box, NULL, debug) && !blob->UniquelyVertical()) {
blob->ClearNeighbours();
small_it.add_to_end(it.extract());
}
}
}
