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/*
* Copyright (c) 2017-2020 ARM Limited.
*
* SPDX-License-Identifier: MIT
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "EqualizeHistogram.h"
namespace arm_compute
{
namespace test
{
namespace validation
{
namespace reference
{
template <typename T>
SimpleTensor<T> equalize_histogram(const SimpleTensor<T> &src)
{
const size_t num_bins = 256; // 0-255 inclusive
std::vector<T> lut(num_bins);
std::vector<uint32_t> hist(num_bins);
std::vector<uint32_t> cd(num_bins); // cumulative distribution
SimpleTensor<T> dst(src.shape(), src.data_type());
// Create the histogram
for(int element_idx = 0; element_idx < src.num_elements(); ++element_idx)
{
hist[src[element_idx]]++;
}
// Calculate cumulative distribution
std::partial_sum(hist.begin(), hist.end(), cd.begin());
// Get the number of pixels that have the lowest non-zero value
const uint32_t cd_min = *std::find_if(hist.begin(), hist.end(), [](const uint32_t &x)
{
return x > 0;
});
const size_t total_num_pixels = cd.back();
// Single color - create linear distribution
if(total_num_pixels == cd_min)
{
std::iota(lut.begin(), lut.end(), 0);
}
else
{
const float diff = total_num_pixels - cd_min;
for(size_t i = 0; i < num_bins; ++i)
{
lut[i] = lround((cd[i] - cd_min) / diff * 255.f);
}
}
// Fill output tensor with equalized values
#if defined(_OPENMP)
#pragma omp parallel for
#endif /* _OPENMP */
for(int i = 0; i < src.num_elements(); ++i)
{
dst[i] = lut[src[i]];
}
return dst;
}
template SimpleTensor<uint8_t> equalize_histogram(const SimpleTensor<uint8_t> &src);
} // namespace reference
} // namespace validation
} // namespace test
} // namespace arm_compute
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