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// Copyright 2016 The Draco Authors.
//
// 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 DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_DELTA_ENCODER_H_
#define DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_DELTA_ENCODER_H_
#include "draco/compression/attributes/prediction_schemes/prediction_scheme_encoder.h"
namespace draco {
// Basic prediction scheme based on computing backward differences between
// stored attribute values (also known as delta-coding). Usually works better
// than the reference point prediction scheme, because nearby values are often
// encoded next to each other.
template <typename DataTypeT, class TransformT>
class PredictionSchemeDeltaEncoder
: public PredictionSchemeEncoder<DataTypeT, TransformT> {
public:
using CorrType =
typename PredictionSchemeEncoder<DataTypeT, TransformT>::CorrType;
// Initialized the prediction scheme.
explicit PredictionSchemeDeltaEncoder(const PointAttribute *attribute)
: PredictionSchemeEncoder<DataTypeT, TransformT>(attribute) {}
PredictionSchemeDeltaEncoder(const PointAttribute *attribute,
const TransformT &transform)
: PredictionSchemeEncoder<DataTypeT, TransformT>(attribute, transform) {}
bool ComputeCorrectionValues(
const DataTypeT *in_data, CorrType *out_corr, int size,
int num_components, const PointIndex *entry_to_point_id_map) override;
PredictionSchemeMethod GetPredictionMethod() const override {
return PREDICTION_DIFFERENCE;
}
bool IsInitialized() const override { return true; }
};
template <typename DataTypeT, class TransformT>
bool PredictionSchemeDeltaEncoder<
DataTypeT, TransformT>::ComputeCorrectionValues(const DataTypeT *in_data,
CorrType *out_corr,
int size,
int num_components,
const PointIndex *) {
this->transform().Init(in_data, size, num_components);
// Encode data from the back using D(i) = D(i) - D(i - 1).
for (int i = size - num_components; i > 0; i -= num_components) {
this->transform().ComputeCorrection(
in_data + i, in_data + i - num_components, out_corr + i);
}
// Encode correction for the first element.
std::unique_ptr<DataTypeT[]> zero_vals(new DataTypeT[num_components]());
this->transform().ComputeCorrection(in_data, zero_vals.get(), out_corr);
return true;
}
} // namespace draco
#endif // DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_DELTA_ENCODER_H_
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