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IDProjectCategoryView StatusLast Update
0000101Siril[All Projects] Sirilpublic2017-03-08 16:42
Reporterlock42Assigned Tolock42 
Status assignedResolutionopen 
PlatformGNU/Linux 64bitsOSDebianOS VersionTesting
Product Version0.9.1 
Target Version1.0.0Fixed in Version 
Summary0000101: Background extraction result needs to be expressed in 32 floating bits
DescriptionSince we have implemented the background extraction module, calculation are done in 32bits integer format. However, the result is stored in a fits structure before applying the correction.
The fits structure is in 16bit. In consequences, information is lost.
A background model image is an extremely smooth function that usually requires a 32-bit format to be represented correctly and in some cases 16-bit is clearly not enough, leading to a posterized image.
In fact, the background model should be generated in 32-bit integer or 64-bit floating point format because sometimes it is exceeding the range of 32-bit floating point.
TagsNo tags attached.


child of 0000103 assignedvinvin Use a more precise format for internal representation of images 



2016-01-22 11:27


m51bug.jpg (1,633,902 bytes)


2016-09-27 16:07

administrator   ~0000357

We should find a workaround by using OPENCV to handle temporary images ....


2017-03-08 16:34

reporter   ~0000367

Wouldn't it be possible to create a virtual background image?
Instead of creating a temporary bitmap, one would create an object that just stores the background formula (polynom?) and calculates pixel values on demand, with whatever precision needed.


2017-03-08 16:42

administrator   ~0000368

Your suggestion matches with previous comment. However changes to do that are a bit tricky. On the other hand, a new library will be implemented for handling 32 and 64bit precisions.
I would suggest you, to workaround this bug, to stretch your image a bit with "Histogram transformation" tool. Indeed, by doing this you enhance dynamic and 16bit is not a problem anymore.

Issue History

Date Modified Username Field Change
2016-01-22 11:19 lock42 New Issue
2016-01-22 11:19 lock42 Status new => assigned
2016-01-22 11:19 lock42 Assigned To => lock42
2016-01-22 11:27 lock42 File Added: m51bug.jpg
2016-01-22 11:31 lock42 Description Updated View Revisions
2016-01-27 11:11 vinvin Relationship added child of 0000103
2016-01-27 11:20 lock42 Target Version 0.9.2 => 1.0.0
2016-09-27 16:07 lock42 Note Added: 0000357
2016-12-19 16:32 lock42 Category General => Software Development
2016-12-19 16:50 lock42 Category Software Development => Software
2016-12-19 23:30 lock42 Category Software => Siril
2017-03-08 16:34 steffens Note Added: 0000367
2017-03-08 16:42 lock42 Note Added: 0000368