77 lines
2.2 KiB
C++
77 lines
2.2 KiB
C++
// File: crn_math.cpp
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// See Copyright Notice and license at the end of inc/crnlib.h
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#include "crn_core.h"
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namespace crnlib
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{
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namespace math
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{
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uint g_bitmasks[32] =
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{
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1U << 0U, 1U << 1U, 1U << 2U, 1U << 3U,
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1U << 4U, 1U << 5U, 1U << 6U, 1U << 7U,
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1U << 8U, 1U << 9U, 1U << 10U, 1U << 11U,
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1U << 12U, 1U << 13U, 1U << 14U, 1U << 15U,
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1U << 16U, 1U << 17U, 1U << 18U, 1U << 19U,
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1U << 20U, 1U << 21U, 1U << 22U, 1U << 23U,
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1U << 24U, 1U << 25U, 1U << 26U, 1U << 27U,
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1U << 28U, 1U << 29U, 1U << 30U, 1U << 31U
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};
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double compute_entropy(const uint8* p, uint n)
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{
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uint hist[256];
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utils::zero_object(hist);
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for (uint i = 0; i < n; i++)
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hist[*p++]++;
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double entropy = 0.0f;
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const double invln2 = 1.0f/log(2.0f);
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for (uint i = 0; i < 256; i++)
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{
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if (!hist[i])
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continue;
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double prob = static_cast<double>(hist[i]) / n;
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entropy += (-log(prob) * invln2) * hist[i];
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}
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return entropy;
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}
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void compute_lower_pow2_dim(int& width, int& height)
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{
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const int tex_width = width;
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const int tex_height = height;
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width = 1;
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for ( ; ; )
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{
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if ((width * 2) > tex_width)
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break;
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width *= 2;
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}
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height = 1;
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for ( ; ; )
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{
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if ((height * 2) > tex_height)
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break;
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height *= 2;
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}
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}
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void compute_upper_pow2_dim(int& width, int& height)
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{
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if (!math::is_power_of_2((uint32)width))
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width = math::next_pow2((uint32)width);
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if (!math::is_power_of_2((uint32)height))
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height = math::next_pow2((uint32)height);
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}
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} // namespace math
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} // namespace crnlib
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