1 // Copyright 2016 The Draco Authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 #ifndef DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_DELTA_ENCODER_H_ 16 #define DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_DELTA_ENCODER_H_ 17 18 #include "draco/compression/attributes/prediction_schemes/prediction_scheme_encoder.h" 19 20 namespace draco { 21 22 // Basic prediction scheme based on computing backward differences between 23 // stored attribute values (also known as delta-coding). Usually works better 24 // than the reference point prediction scheme, because nearby values are often 25 // encoded next to each other. 26 template <typename DataTypeT, class TransformT> 27 class PredictionSchemeDeltaEncoder 28 : public PredictionSchemeEncoder<DataTypeT, TransformT> { 29 public: 30 using CorrType = 31 typename PredictionSchemeEncoder<DataTypeT, TransformT>::CorrType; 32 // Initialized the prediction scheme. PredictionSchemeDeltaEncoder(const PointAttribute * attribute)33 explicit PredictionSchemeDeltaEncoder(const PointAttribute *attribute) 34 : PredictionSchemeEncoder<DataTypeT, TransformT>(attribute) {} PredictionSchemeDeltaEncoder(const PointAttribute * attribute,const TransformT & transform)35 PredictionSchemeDeltaEncoder(const PointAttribute *attribute, 36 const TransformT &transform) 37 : PredictionSchemeEncoder<DataTypeT, TransformT>(attribute, transform) {} 38 39 bool ComputeCorrectionValues( 40 const DataTypeT *in_data, CorrType *out_corr, int size, 41 int num_components, const PointIndex *entry_to_point_id_map) override; GetPredictionMethod()42 PredictionSchemeMethod GetPredictionMethod() const override { 43 return PREDICTION_DIFFERENCE; 44 } IsInitialized()45 bool IsInitialized() const override { return true; } 46 }; 47 48 template <typename DataTypeT, class TransformT> 49 bool PredictionSchemeDeltaEncoder< ComputeCorrectionValues(const DataTypeT * in_data,CorrType * out_corr,int size,int num_components,const PointIndex *)50 DataTypeT, TransformT>::ComputeCorrectionValues(const DataTypeT *in_data, 51 CorrType *out_corr, 52 int size, 53 int num_components, 54 const PointIndex *) { 55 this->transform().Init(in_data, size, num_components); 56 // Encode data from the back using D(i) = D(i) - D(i - 1). 57 for (int i = size - num_components; i > 0; i -= num_components) { 58 this->transform().ComputeCorrection( 59 in_data + i, in_data + i - num_components, out_corr + i); 60 } 61 // Encode correction for the first element. 62 std::unique_ptr<DataTypeT[]> zero_vals(new DataTypeT[num_components]()); 63 this->transform().ComputeCorrection(in_data, zero_vals.get(), out_corr); 64 return true; 65 } 66 67 } // namespace draco 68 69 #endif // DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_DELTA_ENCODER_H_ 70