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sloth85

Converting between 2 byte short and half precision float

5 posts in this topic

I would like to convert from 2 byte shorts tohalf precision floats and vice versa. Are there any functions that can accomplish this?

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Place your input in a conveniently declared structure using DllStructCreate, then read it into variable(s) and place that in another struct with the needed output format.

BTW what do you mean with "half precision float"?

I know float and double but that?


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#3 ·  Posted (edited)

I wanted to respond to this question earlier but was interrupted by a telephone call. I've just been reading about half precision floating-point format on wiki. I haven't quite figured it out yet but will follow this topic with interest.

Edited by czardas

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#4 ·  Posted (edited)

Perhaps if you conveyed the reason you need such a type, you might get.

some suggestions, as far as I am aware, Autoit and dllstruct does not support

such a type as "half precision float".

Edited by JohnOne

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#5 ·  Posted (edited)

Never mind. After some digging I found someone had already written a short to half precision float function on these forums:

I proceeded to port a half precision to short function from C myself:

Func _HalfPrecisionFloat2Short($float)
$float = _WinAPI_FloatToInt($float)
Local $sign = BitAND(BitShift($float, 16), 0x00008000)
Local $exponent = BitAND(BitShift($float, 23), 0x000000ff) - (127 - 15)
Local $fraction = BitAND($float, 0x007fffff)

If $exponent <= 0 Then
If $exponent < -10 Then
If $sign Then
return 0x8000
Else
return 0x0000
EndIf
$fraction = BitShift(BitOR($fraction, 0x00800000), (1-$exponent))
return BitOR($sign, BitShift($fraction, 13))
EndIf
ElseIf $exponent = 0xFF - (127 - 15) Then
If $fraction = 0 Then
return BitOR($sign, 0x7C00)
Else
$fraction = BitShift($fraction, 13)
return BitOR($sign, 0x7C00, $fraction)
EndIf
Else
if $exponent > 30 Then
return BitOR($sign, 0x7C00)
Else
return BitOR($sign, BitShift($exponent, -10), BitShift($fraction, 13))
EndIf
EndIf
EndFunc
Edited by sloth85

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