You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
50 lines
1.2 KiB
50 lines
1.2 KiB
11 years ago
|
#pragma once
|
||
|
|
|
||
|
|
namespace jcmp {
|
||
|
|
// input in [0, 1], output [0, 255]
|
||
|
|
inline uint8_t clamp_round(double x){
|
||
|
|
if(x <= 0.0) return 0;
|
||
|
|
if(x >= 1.0) return 255;
|
||
|
|
return uint8_t(std::round(255.0*x));
|
||
|
|
}
|
||
|
|
|
||
|
|
// parameters which need to be stored in the file
|
||
|
|
// to be able to dequantize
|
||
|
|
struct quantize_params {
|
||
|
|
double f_max_abs;
|
||
|
|
double f_min_abs;
|
||
|
|
};
|
||
|
|
|
||
|
|
// Quantization may be non linear (given by f and f_inv)
|
||
|
|
struct quantization {
|
||
|
|
std::function<double(double)> f;
|
||
|
|
std::function<double(double)> f_inv;
|
||
|
|
quantize_params p;
|
||
|
|
|
||
|
|
quantization() = default;
|
||
|
|
|
||
|
|
template <typename F>
|
||
|
|
quantization(F const & f_, F const & f_inv_, double max_abs, double min_abs)
|
||
|
|
: f(f_)
|
||
|
|
, f_inv(f_inv_)
|
||
|
|
, p{f(max_abs), f(min_abs)}
|
||
|
|
{}
|
||
|
|
|
||
|
|
uint8_t forwards(double x){
|
||
|
|
double y = std::abs(x);
|
||
|
|
y = (f(y) - p.f_min_abs) / (p.f_max_abs - p.f_min_abs);
|
||
|
|
if(x < 0) y = -y;
|
||
|
|
return clamp_round(0.5 * (y + 1.0));
|
||
|
|
}
|
||
|
|
|
||
|
|
double backwards(uint8_t x){
|
||
|
|
double y = 2.0 * x / 255.0 - 1.0;
|
||
|
|
y = (p.f_max_abs - p.f_min_abs) * y;
|
||
|
|
if(y < 0) return -f_inv(-y + p.f_min_abs);
|
||
|
|
return f_inv(y + p.f_min_abs);
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
static_assert(sizeof(quantize_params) == 16, "struct not propery packed");
|
||
|
|
}
|