| 02 May 2016 01:59 AM |
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Hello,
is it possible that the new versions of Envi (>=5) always include the NoData value in the stretching even if it is specified in the file?
I have a Landsat image with a lot of NoData values (-9999) and I only see my data as black and the NoData areas as white... no stretch can change this. Custom stretch does not work (doesnt show me any data). In QGIS or the classic Envi, its no problem!
Cheers, Kim
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MariM
Veteran Member
Posts:2396  
| 02 May 2016 05:13 AM |
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Did you specify the value of -9999 as the 'Data value to ignore' in the header file? This should make those values transparent for display.
If you zoom into an area of valid data only, then perform a stretch on the extents in 5.x, does the data display?
If you cannot get your data to display, can you calculate the statistics on the file and post the results?
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Deleted User
New Member
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| 02 May 2016 09:06 AM |
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Yes, the data ignore value is set to -9999 in the header.
The 3 stretch buttons, where you can also stretch to display extent are greyed out. When I perform a raster color slice, the data becomes visible but of course I would prefer a simple stretch.
These are the quick stats: min: -6307, max: 6768, mean: 2098
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Deleted User
Basic Member
Posts:228 
| 02 May 2016 01:29 PM |
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I am guessing that if the buttons that allow you to choose the image extent used to calculate the stretch are grayed out, it is probably because "No Stretch" is currently chosen for the stretch type. Try changing the stretch type to some kind of stretch, and then see if you can zoom so that only a part of the image that has no values of -9999 is in the display, and choose Stretch on View Extent. This should make the data appear.
- Peg
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Deleted User
New Member
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| 03 May 2016 04:37 AM |
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No, the buttons are also grayed out in an e.g. Linear 2% stretch...
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MariM
Veteran Member
Posts:2396
| 03 May 2016 06:02 AM |
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Is the image a TIFF image with a palette?
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Deleted User
New Member
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| 04 May 2016 12:44 AM |
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No, it is an ENVI bsq.
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