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81 lines
3.2 KiB
C++
81 lines
3.2 KiB
C++
// Copyright 2011 Google Inc. All Rights Reserved.
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// Author: rays@google.com (Ray Smith)
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///////////////////////////////////////////////////////////////////////
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// File: intfeaturedist.h
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// Description: Fast set-difference-based feature distance calculator.
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// Created: Thu Sep 01 12:14:30 PDT 2011
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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///////////////////////////////////////////////////////////////////////
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#ifndef TESSERACT_CLASSIFY_INTFEATUREDIST_H_
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#define TESSERACT_CLASSIFY_INTFEATUREDIST_H_
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#include "genericvector.h"
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namespace tesseract {
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class IntFeatureMap;
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// Feature distance calculator designed to provide a fast distance calculation
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// based on set difference between a given feature set and many other feature
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// sets in turn.
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// Representation of a feature set as an array of bools that are sparsely
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// true, and companion arrays that allow fast feature set distance
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// calculations with allowance of offsets in position.
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// Init is expensive, so for greatest efficiency, to re-initialize for a new
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// feature set, use Set(..., false) on the SAME feature set as was used to
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// setup with Set(..., true), to return to its initialized state before
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// reuse with Set(..., true) on a new feature set.
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class IntFeatureDist {
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public:
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IntFeatureDist();
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~IntFeatureDist();
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// Initialize the bool array to the given size of feature space.
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// The feature_map is just borrowed, and must exist for the entire
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// lifetime of the IntFeatureDist.
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void Init(const IntFeatureMap* feature_map);
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// Setup the map for the given indexed_features that have been indexed by
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// feature_map. After use, use Set(..., false) to reset to the initial state
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// as this is faster than calling Init for sparse spaces.
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void Set(const GenericVector<int>& indexed_features,
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int canonical_count, bool value);
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// Compute the distance between the given feature vector and the last
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// Set feature vector.
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double FeatureDistance(const GenericVector<int>& features) const;
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double DebugFeatureDistance(const GenericVector<int>& features) const;
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private:
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// Clear all data.
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void Clear();
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// Size of the indexed feature space.
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int size_;
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// Total weight of features currently stored in the maps.
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double total_feature_weight_;
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// Pointer to IntFeatureMap given at Init to find offset features.
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const IntFeatureMap* feature_map_;
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// Array of bools indicating presence of a feature.
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bool* features_;
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// Array indicating the presence of a feature offset by one unit.
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bool* features_delta_one_;
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// Array indicating the presence of a feature offset by two units.
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bool* features_delta_two_;
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};
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} // namespace tesseract
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#endif // TESSERACT_CLASSIFY_INTFEATUREDIST_H_
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