/// <summary>
/// Convert a 16-bit float (passed as a UInt16) to
/// a float. The 16-bit float has a 9-bit mantissa, a 6-bit expontent
/// and a sign bit. The format is similar to the IEEE-754 but in 16-bit
/// form. The exponent uses a bias of 31 insead of 127. The mantissa
/// is the upper 9-bits of a IEEE-754 32-bit float mantissa.
/// </summary>
/// <param name="float16">The float16 in and unsigned 16-bit format.</param>
/// <returns>a 32-bit float.</returns>
public static UInt16 float32ToFloat16(float value)
{
UInt32 float16 = 0;
FloatUIntStruct fltIntVal = new FloatUIntStruct();
fltIntVal.floatValue = value;
UInt32 mant = fltIntVal.uintValue & 0x007fffff;
Int32 exp = (Int32)(fltIntVal.uintValue >> 23) & 0xff;
if (exp == 0) //Max value
{
return(0); //Max value
}
exp -= 127;
if (exp > 31)
{
return((UInt16)0x7E00); //Max positive value
}
else if (exp < -31)
{
return((UInt16)0xFE00); //Max negative value
}
else
{
mant = mant >> 14;
exp = (exp + 31) & 0x3F;
float16 = mant + (UInt32)(exp << 9);
if ((fltIntVal.uintValue & 0x80000000) != 0)
{
float16 = float16 | 0x8000;
}
}
return((UInt16)float16);
}
/// <summary>
/// Convert a 16-bit float (passed as a UInt16) to
/// a float. The 16-bit float has a 9-bit mantissa, a 6-bit expontent
/// and a sign bit. The format is similar to the IEEE-754 but in 16-bit
/// form. The exponent uses a bias of 31 insead of 127. The mantissa
/// is the upper 9-bits of a IEEE-754 32-bit float mantissa.
/// </summary>
/// <param name="float16">The float16 in and unsigned 16-bit format.</param>
/// <returns>a 32-bit float.</returns>
public static float float16ToFloat32(UInt16 float16)
{
FloatUIntStruct fltIntVal = new FloatUIntStruct();
fltIntVal.uintValue = 0;
UInt32 mant = (UInt32)float16 & 0x01ff;
Int32 exp = (Int32)((float16 & 0x7E00)) >> 9;
if (exp == 0x2F) //Max value
{
fltIntVal.floatValue = (float)1.0e32;
if ((float16 & 0x8000) != 0)
{
fltIntVal.uintValue |= 0x80000000;
}
return((float)1.0e32); //Max value
}
else if (exp == 0)
{
if (mant == 0)
{
fltIntVal.floatValue = (float)0.0;
return(fltIntVal.floatValue);
}
else
{
//we are at our smallest 16-bit float value...
//re-adjust mantissa and exp for 32-bit float;
exp = -31;
for (int i = 0; i < 9; ++i)
{
mant = mant << 1;
--exp;
if ((mant & 0x0200) != 0)
{
break;
}
}
}
}
else
{
exp = exp - 31; //bias of 31.
}
mant = mant & 0x1FF;
mant = mant << 14; //IEEE-754 mantisa
exp = exp + 127; //IEEE-754 exp bias.
fltIntVal.uintValue = ((UInt32)exp << 23) + mant;
if ((float16 & 0x8000) != 0)
{
fltIntVal.uintValue |= 0x80000000;
}
return(fltIntVal.floatValue);
}
