101 lines
3.8 KiB
C++
101 lines
3.8 KiB
C++
/*
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "ModeFilter.h"
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// Constructor
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template <class T, uint8_t FILTER_SIZE>
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ModeFilter<T,FILTER_SIZE>::ModeFilter(uint8_t return_element) :
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FilterWithBuffer<T,FILTER_SIZE>(),
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_return_element(return_element),
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drop_high_sample(true)
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{
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// ensure we have a valid return_nth_element value. if not, revert to median
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if ( _return_element >= FILTER_SIZE ) {
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_return_element = FILTER_SIZE / 2;
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}
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}
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// Public Methods //////////////////////////////////////////////////////////////
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template <class T, uint8_t FILTER_SIZE>
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T ModeFilter<T,FILTER_SIZE>::apply(T sample)
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{
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// insert the new items into the samples buffer
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isort(sample, drop_high_sample);
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// next time drop from the other end of the sample buffer
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drop_high_sample = !drop_high_sample;
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// return results
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if (FilterWithBuffer<T,FILTER_SIZE>::sample_index < FILTER_SIZE ) {
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// middle sample if buffer is not yet full
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return _output = FilterWithBuffer<T,FILTER_SIZE>::samples[(FilterWithBuffer<T,FILTER_SIZE>::sample_index / 2)];
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} else {
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// return element specified by user in constructor
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return _output = FilterWithBuffer<T,FILTER_SIZE>::samples[_return_element];
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}
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}
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//
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// insertion sort - takes a new sample and pushes it into the sample array
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// drops either the highest or lowest sample depending on the 'drop_high_sample' parameter
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//
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template <class T, uint8_t FILTER_SIZE>
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void ModeFilter<T,FILTER_SIZE>::isort(T new_sample, bool drop_high)
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{
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int8_t i;
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// if the buffer isn't full simply increase the #items in the buffer (i.e. sample_index)
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// the rest is the same as dropping the high sample
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if ( FilterWithBuffer<T,FILTER_SIZE>::sample_index < FILTER_SIZE ) {
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FilterWithBuffer<T,FILTER_SIZE>::sample_index++;
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drop_high = true;
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}
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if ( drop_high ) { // drop highest sample from the buffer to make room for our new sample
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// start from top. Note: sample_index always points to the next open space so we start from sample_index-1
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i = FilterWithBuffer<T,FILTER_SIZE>::sample_index-1;
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// if the next element is higher than our new sample, push it up one position
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while (i > 0 && FilterWithBuffer<T,FILTER_SIZE>::samples[i-1] > new_sample) {
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FilterWithBuffer<T,FILTER_SIZE>::samples[i] = FilterWithBuffer<T,FILTER_SIZE>::samples[i-1];
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i--;
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}
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// add our new sample to the buffer
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FilterWithBuffer<T,FILTER_SIZE>::samples[i] = new_sample;
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} else { // drop lowest sample from the buffer to make room for our new sample
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// start from the bottom
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i = 0;
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// if the element is lower than our new sample, push it down one position
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while ( i < FilterWithBuffer<T,FILTER_SIZE>::sample_index-1 && FilterWithBuffer<T,FILTER_SIZE>::samples[i+1] < new_sample ) {
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FilterWithBuffer<T,FILTER_SIZE>::samples[i] = FilterWithBuffer<T,FILTER_SIZE>::samples[i+1];
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i++;
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}
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// add our new sample to the buffer
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FilterWithBuffer<T,FILTER_SIZE>::samples[i] = new_sample;
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}
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}
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// instantiate required implementations
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template class ModeFilter<float,5>;
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template class ModeFilter<int16_t,5>;
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