Ticket #1422 (closed defect: fixed)
Opened 2012-08-17T15:18:04-05:00
Last modified 2012-08-20T15:09:05-05:00
Signed 16-bit images don't survive IJ2->IJ1->IJ2 round trip
| Reported by: | aivar | Owned by: | bdezonia |
|---|---|---|---|
| Priority: | minor | Milestone: |
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| Component: | Core | Version: | |
| Severity: | serious | Keywords: | |
| Cc: | Blocked By: | ||
| Blocking: | #1420 |
Description
Create a test ramp image (File\New\Image) with signed 16-bit, the image looks fine with a grayscale ramp, but if you apply a LUT (Image/Lookup Tables/Fire) the LUT range is distorted.
(This is the second screen capture in luts.png, attached to parent ticket 1420.)
The range of values for the ramp image remains -32768 to 32767. (Unlike the other bugs associated with 1420 these values do not change from the roundtrip.)
I tracked the bug as far as ColorTableHarmonizer.assignChannelMinMax(). The line 'mn = imp.getDisplayRangeMin();' sets minimum to 0.0 and 'mx = imp.getDisplayRangeMax();' sets maximum to 32767.0. Next assignChannelMinMax subtracts 32768 from each (I think to convert unsigned to signed?), winding up with a range of -32768.0...-1.0. This range is used to apply the LUT, since it's about half what it should be the LUT ramp only goes halfway. It seems ImagePlus is reporting min/max wrong.
Change History
comment:2 Changed 2012-08-20T15:09:05-05:00 by bdezonia
- Status changed from new to closed
- Resolution set to fixed
IJ2 was setting min max in ImagePlus to -32768,32767. But IJ1 truncs all negative display range values to 0 when dealing with 16-bit data. Make sure that when we set display range on 16-bit data we take into account the preencoded signedness of the data. Fixed with commit 2784318b663641c147c20ffcfe0fff187d1efe92