[Insight-users] Truncating floating point in SimpleITK

[David Welch]

I'm trying to make the images more compressible by removing the unneeded
precision.  Like I said, it was a naive approach. ;-)

I ended up using sitk.GetArrayFromImage() and numpy's around() function on
the array.  I was looking at the decimal module for a bit, but this was
simpler.  I'm still testing to see if it makes any difference,

Thanks all,
Dave

On Thu, Jun 27, 2013 at 1:03 PM, Bradley Lowekamp <brad at lowekamp.net> wrote:

> Dave,
>
> Could it be just that you are thinking base 10 and not base 2? What do
> other numbers look like after the tranuncation?
>
> On Jun 27, 2013, at 10:27 AM, David Welch <david.m.welch at gmail.com> wrote:
>
> Hey all,
>
> I have some images that represent probability (values between 0.0 and 1.0)
> and I'd like to drop the unneeded precision from the Float32 values.
> Here's my naive approach:
>
> def truncate(image, ndigits=0):
>     """ Truncate to the given number of digits """
>     factor = 10 ** ndigits
>     scaled = image * factor
>     casted = sitk.Cast(scaled, sitk.sitkUInt32)
>     truncated = sitk.Cast(casted, image.GetPixelIDValue()) / float(factor)
>     return truncated
>
> ## Test
> test = truncate(img, 4)
> print img[128,188,196]
> print test[128,188,196]
>
> 0.700903475285
>
> 0.700900018215
>
> What am I doing wrong?  Any ideas?
>
>
> Cheers,
>
> Dave W.
>
>
>
>
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