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