Function hist_equal

src/api/c/histeq.cpp:43–77

template<typename T, typename hType>
static af_array hist_equal(const af_array& in, const af_array& hist) {
    const Array<T> input = getArray<T>(in);

    af_array vInput = 0;
    AF_CHECK(af_flat(&vInput, in));

    Array<float> fHist = cast<float>(getArray<hType>(hist));

    const dim4& hDims = fHist.dims();
    dim_t grayLevels  = fHist.elements();

    Array<float> cdf = scan<af_add_t, float, float>(fHist, 0);

    float minCdf = getScalar<float>(reduce_all<af_min_t, float, float>(cdf));
    float maxCdf = getScalar<float>(reduce_all<af_max_t, float, float>(cdf));
    float factor = static_cast<float>(grayLevels - 1) / (maxCdf - minCdf);

    // constant array of min value from cdf
    Array<float> minCnst = createValueArray<float>(hDims, minCdf);
    // constant array of factor variable
    Array<float> facCnst = createValueArray<float>(hDims, factor);
    // cdf(i) - min for all elements
    Array<float> diff = arithOp<float, af_sub_t>(cdf, minCnst, hDims);
    // multiply factor with difference
    Array<float> normCdf = arithOp<float, af_mul_t>(diff, facCnst, hDims);
    // index input array with normalized cdf array
    Array<float> idxArr = lookup<float, T>(normCdf, getArray<T>(vInput), 0);

    Array<T> result = cast<T>(idxArr);
    result          = modDims(result, input.dims());

    AF_CHECK(af_release_array(vInput));

    return getHandle<T>(result);
}

af_err af_hist_equal(af_array* out, const af_array in, const af_array hist) {
    try {