transform_cross_correlate() [1/2]

template<OperationReadyData DataType>

DataType MayaFlux::Yantra::transform_cross_correlate	(	DataType &	input,
		const std::vector< double > &	template_signal,
		bool	normalize,
		std::vector< std::vector< double > > &	working_buffer
	)

Cross-correlation using FFT (convolution with time-reversed impulse) (OUT-OF-PLACE)

Template Parameters

DataType

OperationReadyData type

Parameters

input	Input data - will NOT be modified
template_signal	Template signal for correlation
normalize	Whether to normalize the result
working_buffer	Buffer for operations (will be resized if needed)

Returns

Cross-correlated data

Definition at line 284 of file ConvolutionHelper.hpp.

{
    auto [target_data, structure_info] = OperationHelper::setup_operation_buffer(input, working_buffer);
 
    std::vector<double> reversed_template(template_signal.rbegin(), template_signal.rend());
 
    auto correlation_op = [](const Eigen::VectorXcd& input_fft,
                              const Eigen::VectorXcd& kernel_fft,
                              Eigen::VectorXcd& result_fft) {
        std::ranges::transform(input_fft, kernel_fft, result_fft.begin(),
            [](const std::complex<double>& a, const std::complex<double>& b) {
                return a * std::conj(b);
            });
    };
 
    for (size_t i = 0; i < target_data.size(); ++i) {
        auto result = fft_convolve_helper(target_data[i], reversed_template, correlation_op);
 
        if (normalize && !result.empty()) {
            auto [min_it, max_it] = std::ranges::minmax_element(result);
            double max_abs = std::max(std::abs(*min_it), std::abs(*max_it));
            if (max_abs > 0.0) {
                std::ranges::transform(result, result.begin(),
                    [max_abs](double val) { return val / max_abs; });
            }
        }
 
        working_buffer[i].resize(result.size());
        working_buffer[i] = std::move(result);
    }
 
    return OperationHelper::reconstruct_from_double<DataType>(working_buffer, structure_info);
}

References fft_convolve_helper(), MayaFlux::normalize(), and MayaFlux::Yantra::OperationHelper::setup_operation_buffer().

Here is the call graph for this function: