<font><font face="verdana,sans-serif">PNG has three following units: meters, radians, and unknown. Currently PNG reader ignores unit, and writes unknown units.</font></font><div><font><font face="verdana,sans-serif"><br></font></font></div>
<div><font face="verdana, sans-serif">I guess I Should keep writing unknown units. But when reading PNG with meter units (eg. 2000 pixels/meter), should I transform it into pixel spacing 0.5 (assuming customary millimeter) or into 0.0005?</font></div>
<div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Dec 11, 2012 at 3:36 PM, Bill Lorensen <span dir="ltr"><<a href="mailto:bill.lorensen@gmail.com" target="_blank">bill.lorensen@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">No units. ITK considers units an application thing. You can add a unit<br>
type if the format supports it. It could help applications. For<br>
example, most medical images use mm's.<br>
<div class="HOEnZb"><div class="h5"><br>
On Tue, Dec 11, 2012 at 8:25 AM, Dženan Zukić <<a href="mailto:dzenanz@gmail.com">dzenanz@gmail.com</a>> wrote:<br>
> Is ITK still assuming no units, or millimeters are units for pixel spacing?<br>
><br>
><br>
> On Mon, Dec 10, 2012 at 5:25 PM, Bill Lorensen <<a href="mailto:bill.lorensen@gmail.com">bill.lorensen@gmail.com</a>><br>
> wrote:<br>
>><br>
>> If you submit a gerrit patch, I'll write or modify a test.<br>
>><br>
>> How will we know if the fix works unless we test it? How will we know<br>
>> if someone reintroduces the bug if we don't test it?<br>
>><br>
>><br>
>> On Mon, Dec 10, 2012 at 10:41 AM, Dženan Zukić <<a href="mailto:dzenanz@gmail.com">dzenanz@gmail.com</a>> wrote:<br>
>> > But this would be a bug fix, not a patch introducing new features. This<br>
>> > should already be working, and ideally having a test.<br>
>> ><br>
>> > I know that many bugs don't get fixed, because they are not important<br>
>> > enough<br>
>> > and there is not enough people working on ITK. However a requirement to<br>
>> > write a 20-30 line test for a few lines of fixed code is a great<br>
>> > deterrence<br>
>> > for me to contribute bug fixes (such as this one).<br>
>> ><br>
>> ><br>
>> > On Mon, Dec 10, 2012 at 4:26 PM, Bill Lorensen <<a href="mailto:bill.lorensen@gmail.com">bill.lorensen@gmail.com</a>><br>
>> > wrote:<br>
>> >><br>
>> >> Looks like ti should be fixed. But if you submit a gerrit patch, make<br>
>> >> sure oyu also supply a test or modify an existing test.<br>
>> >><br>
>> >> The lack of a test is why your previous gerrit patch has not been<br>
>> >> approved.<br>
>> >><br>
>> >> Bill<br>
>> >><br>
>> >> On Mon, Dec 10, 2012 at 8:35 AM, Dženan Zukić <<a href="mailto:dzenanz@gmail.com">dzenanz@gmail.com</a>><br>
>> >> wrote:<br>
>> >> > Hi everyone,<br>
>> >> ><br>
>> >> > I have noticed that ImageFileWriter, when writing png format, writes<br>
>> >> > wrong<br>
>> >> > pixel size information. It is not completely wrong, but it is not in<br>
>> >> > accordance with png specification.<br>
>> >> ><br>
>> >> > When reading such files with OpenCV, I get following warning:<br>
>> >> > libpng warning: Invalid sCAL ignored: invalid unit<br>
>> >> > This is not just annoying and clutter-causing, but displaying it for<br>
>> >> > every<br>
>> >> > single image slows down my OpenCV processing.<br>
>> >> ><br>
>> >> > I used XnView to batch-edit the extracted slices and set some scaling<br>
>> >> > which<br>
>> >> > adheres to the specification to get rid of this warning.<br>
>> >> ><br>
>> >> > Now the question: should I correct this bug, or submit a bug report?<br>
>> >> > My<br>
>> >> > last<br>
>> >> > bug-fixing ended non-gloriously :(<br>
>> >> ><br>
>> >> > _____________________________________<br>
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>> >> ><br>
>> >> > Please keep messages on-topic and check the ITK FAQ at:<br>
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>> >><br>
>> >><br>
>> >><br>
>> >> --<br>
>> >> Unpaid intern in BillsBasement at noware dot com<br>
>> ><br>
>> ><br>
>><br>
>><br>
>><br>
>> --<br>
>> Unpaid intern in BillsBasement at noware dot com<br>
><br>
><br>
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Unpaid intern in BillsBasement at noware dot com<br>
</div></div></blockquote></div><br></div>