Normalized Integer to/from Float Conversion

问题

I need to convert normalized integer values to and from real floating-point values. For instance, for int16_t, a value of 1.0 is represented by 32767 and -1.0 is represented by -32768. Although it's a bit tedious to do this for each integer type, both signed and unsigned, it's still easy enough to write by hand.

However, I want to use standard methods whenever possible rather than going off and reinventing the wheel, so what I'm looking for is something like a standard C or C++ header, a Boost library, or some other small, portable, easily-incorporated source that already performs these conversions.

回答1:

Here's a templated solution using std::numeric_limits:

#include <cstdint>
#include <limits>

template <typename T>
constexpr double normalize (T value) {
  return value < 0
    ? -static_cast<double>(value) / std::numeric_limits<T>::min()
    :  static_cast<double>(value) / std::numeric_limits<T>::max()
    ;
}

int main () {
  // Test cases evaluated at compile time.
  static_assert(normalize(int16_t(32767)) == 1, "");
  static_assert(normalize(int16_t(0)) == 0, "");
  static_assert(normalize(int16_t(-32768)) == -1, "");
  static_assert(normalize(int16_t(-16384)) == -0.5, "");
  static_assert(normalize(uint16_t(65535)) == 1, "");
  static_assert(normalize(uint16_t(0)) == 0, "");
}

This handles both signed and unsigned integers, and 0 does normalize to 0.

View Successful Compilation Result

回答2:

Although it's a bit tedious to do this for each integer type, both signed and unsigned, it's still easy enough to write by hand.

You certainly don't need to do this for each integer type! Use <limits> instead.

template<class T> double AsDouble(const T x) {
    const double valMin = std::numeric_limits<T>::min();
    const double valMax = std::numeric_limits<T>::max();
    return 2 * (x - valMin) / (valMax - valMin) - 1; // note: 0 does not become 0.
}

来源：https://stackoverflow.com/questions/37580501/normalized-integer-to-from-float-conversion

标签

c++

floating-point

integer