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On 5/8/2012 9:05 PM, Michael Droettboom wrote:
<blockquote cite="mid:4FA9DF0A.1080600@stsci.edu" type="cite">
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It actually appears that this is converting 32-bit integers to
64-bit floats. Does the file have BZERO or BSCALE specified? If
so, it is normal behavior to convert to 64-bit floats so that user
code doesn't have to deal with offset and scaling issues.<br>
<br>
Mike<br>
</blockquote>
<br>
Thanks Mike. <br>
<br>
The FITS files do have BZERO and BSCALE defined. My mistake (twice)
saying 32-bit float since BITPIX=+32. I was expecting conversion to
32-bit floats. Since converting 32-bit integers to 64-bit floats is
the standard Pyfits behavior, I will perform the conversion
explicitly (numpy astype).<br>
<br>
-- jv<br>
<br>
<br>
<br>
<br>
<br>
<blockquote cite="mid:4FA9DF0A.1080600@stsci.edu" type="cite"> <br>
On 05/08/2012 02:14 PM, Jim Vickroy wrote:
<blockquote cite="mid:4FA96276.6060506@noaa.gov" type="cite">
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On 5/8/2012 11:11 AM, Philip Tait wrote:
<blockquote
cite="mid:4fa953d2.4574b60a.76bc.ffffc485@mx.google.com"
type="cite">Isn't this a known issue, fixed in 3.0.7?<br>
</blockquote>
<br>
Thanks for the quick reply. It is embarrassing to post a
problem and not be using the latest release. So I've
downloaded/installed 3.0.7. Unfortunately, the same behavior
persists (i.e., unwanted, silent conversion from 32 to 64 bit
floats) as illustrated below:<br>
<br>
>>> import os<br>
>>> import sys<br>
>>> import pyfits<br>
>>> sys.version<br>
'2.6.4 (r264:75708, Oct 26 2009, 08:23:19) [MSC v.1500 32 bit
(Intel)]'<br>
>>> pyfits.__version__<br>
'3.0.7'<br>
>>> path = ...<br>
>>> HDUs = pyfits.open (path,mode='readonly')<br>
>>> HDUs['primary'].header['bitpix']<br>
32<br>
>>> HDUs['primary'].data.dtype<br>
dtype('float64')<br>
>>> HDUs['primary'].header['bitpix']<br>
-64<br>
>>> <br>
<br>
Is this a bug that should be reported?<br>
<br>
Thanks,<br>
-- jv<br>
<br>
<br>
<br>
<br>
<br>
<br>
<blockquote
cite="mid:4fa953d2.4574b60a.76bc.ffffc485@mx.google.com"
type="cite"><br>
<span style="font-family:Prelude, Verdana, san-serif;"><br>
<br>
</span><span id="signature">
<div style="font-family: arial, sans-serif; font-size:
12px;color: #999999;">-- Sent from my HP Pre3</div>
<br>
</span><span style="color:navy; font-family:Prelude, Verdana,
san-serif; ">
<hr style="width:75%" align="left">On May 8, 2012 6:59, Jim
Vickroy <a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:jim.vickroy@noaa.gov"><jim.vickroy@noaa.gov></a>
wrote: <br>
<br>
</span>Hi Pyfits users, <br>
<br>
Consider: <br>
<br>
>>> import pyfits <br>
>>> pyfits.__version__ <br>
'3.0.5' <br>
>>> path = ... <br>
>>> HDUs = pyfits.open (path,mode='readonly') <br>
>>> HDUs['primary'].header['bitpix'] <br>
32 <br>
>>> HDUs['primary'].data.dtype <br>
dtype('float64') <br>
>>> HDUs['primary'].header['bitpix'] <br>
-64 <br>
>>> <br>
<br>
Why is the conversion from 32 to 64 bit floats silently
occurring? How <br>
can I prevent it? <br>
<br>
Thanks, <br>
-- jv <br>
<br>
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