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// File: ccnontextdetect.h
// Description: Connected-Component-based non-text detection.
// Copyright 2011 Google Inc. All Rights Reserved.
// Author: rays@google.com (Ray Smith)
// Created: Sat Jun 11 09:52:01 PST 2011
//
// 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_CCPHOTODETECT_H_
#define TESSERACT_TEXTORD_CCPHOTODETECT_H_
#include "blobgrid.h"
#include "scrollview.h"
namespace tesseract {
// The CCNonTextDetect class contains grid-based operations on blobs to create
// a full-resolution image mask analogous yet complementary to
// pixGenHalftoneMask as it is better at line-drawings, graphs and charts.
class CCNonTextDetect : public BlobGrid {
public:
CCNonTextDetect(int gridsize, const ICOORD& bleft, const ICOORD& tright);
virtual ~CCNonTextDetect();
// Creates and returns a Pix with the same resolution as the original
// in which 1 (black) pixels represent likely non text (photo, line drawing)
// areas of the page, deleting from the blob_block the blobs that were
// determined to be non-text.
// The photo_map (binary image mask) is used to bias the decision towards
// non-text, rather than supplying a definite decision.
// The blob_block is the usual result of connected component analysis,
// holding the detected blobs.
// The returned Pix should be PixDestroyed after use.
Pix* ComputeNonTextMask(bool debug, Pix* photo_map, TO_BLOCK* blob_block);
private:
// Computes and returns the noise_density IntGrid, at the same gridsize as
// this by summing the number of small elements in a 3x3 neighbourhood of
// each grid cell. good_grid is filled with blobs that are considered most
// likely good text, and this is filled with small and medium blobs that are
// more likely non-text.
// The photo_map is used to bias the decision towards non-text, rather than
// supplying definite decision.
IntGrid* ComputeNoiseDensity(bool debug, Pix* photo_map, BlobGrid* good_grid);
// 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
void MarkAndDeleteNonTextBlobs(BLOBNBOX_LIST* blobs,
int max_blob_overlaps,
ScrollView* win, ScrollView::Color ok_color,
Pix* nontext_mask);
// Returns true if the given blob overlaps more than max_overlaps blobs
// in the current grid.
bool BlobOverlapsTooMuch(BLOBNBOX* blob, int max_overlaps);
// Max entry in noise_density_ before the cell is declared noisy.
int max_noise_count_;
// Completed noise density map, which we keep around to use for secondary
// noise detection.
IntGrid* noise_density_;
};
} // namespace tesseract.
#endif // TESSERACT_TEXTORD_CCPHOTODETECT_H_
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