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OpenCV-Erlang/Elixir binding.

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evision c_src modules evision_backend bit_unary.h
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c_src/modules/evision_backend/bit_unary.h 

#ifndef EVISION_BACKEND_BIT_UNARY_H

#define EVISION_BACKEND_BIT_UNARY_H



#include <cstdint>

#include <type_traits>

#include <erl_nif.h>

#include "../../ArgInfo.hpp"

#include "../evision_mat_utils.hpp"



static inline int evision_popcount_u64(uint64_t x) {

    int c = 0;

    while (x) { c += (int)(x & 1); x >>= 1; }

    return c;

}



static inline int evision_clz_width(uint64_t x, int width) {

    int c = 0;

    for (int b = width - 1; b >= 0; b--) {

        if (x & ((uint64_t)1 << b)) break;

        c++;

    }

    return c;

}



// Per-element bit op preserving the integer type (Nx.count_leading_zeros /

// population_count). op 0 = clz (within the type's bit width), 1 = popcount. The

// element's raw bits are read as unsigned, matching Nx's unsigned read; the count

// is written back in the same type.

template <typename T>

static void evision_bit_unary(cv::Mat &m, int op) {

    typedef typename std::make_unsigned<T>::type U;

    T *p = (T *)m.data;

    size_t n = m.total();

    int width = (int)(sizeof(T) * 8);

    for (size_t i = 0; i < n; i++) {

        uint64_t x = (uint64_t)(U)p[i];

        int r = (op == 0) ? evision_clz_width(x, width) : evision_popcount_u64(x);

        p[i] = (T)r;

    }

}



// @evision c: mat_bit_unary, evision_cv_mat_bit_unary, 1

// @evision nif: def mat_bit_unary(_opts \\ []), do: :erlang.nif_error(:undefined)

static ERL_NIF_TERM evision_cv_mat_bit_unary(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {

    using namespace cv;

    using namespace evision::nif;

    std::map<std::string, ERL_NIF_TERM> erl_terms;

    int nif_opts_index = 0;

    evision::nif::parse_arg(env, nif_opts_index, argv, erl_terms);



    {

        Mat src;

        int op = 0;



        if (evision_to_safe(env, evision_get_kw(env, erl_terms, "src"), src, ArgInfo("src", 0)) &&

            evision_to_safe(env, evision_get_kw(env, erl_terms, "op"), op, ArgInfo("op", 0))) {

            Mat dst = src.clone();

            switch (dst.depth()) {

                case CV_8U:  evision_bit_unary<uint8_t>(dst, op); break;

                case CV_8S:  evision_bit_unary<int8_t>(dst, op); break;

                case CV_16U: evision_bit_unary<uint16_t>(dst, op); break;

                case CV_16S: evision_bit_unary<int16_t>(dst, op); break;

                case CV_32S: evision_bit_unary<int32_t>(dst, op); break;

                case CV_32U: evision_bit_unary<uint32_t>(dst, op); break;

                case CV_64S: evision_bit_unary<int64_t>(dst, op); break;

                case CV_64U: evision_bit_unary<uint64_t>(dst, op); break;

                default: return evision::nif::error(env, "mat_bit_unary: integer types only");

            }

            return evision_from(env, dst);

        }

    }



    return enif_make_badarg(env);

}



#endif // EVISION_BACKEND_BIT_UNARY_H