FITs image read broken for 16bit unsigned images
Posted: Tue Feb 03, 2004 11:30 am
I cannot get XnView to correctly read 16bit unsigned FITs files (as produced by the Starlight Express cameras).
These files have BITPIX = 16, and BZERO = 32768
XnView interprets them as 8bit images, discarding all the negative value pixel information. That is it appears to ignore the BZERO field in the header.
If I understand the standard correctly, when reading a FITs file you should add BZERO (32768 in this case) to every pixel value. For these files this will bring the pixel value range to 0-64k.
The FITs plugin for Photoshop can read these files correctly.
I can supply sample image files if required.
Also the FITS standard does not define the origin of the image and different software packages assume either top-left or bottom-left as the origin resulting in inverted images when reading the same file in different packages. Would it be possible to add the customization of the origin into the XnView configuration?
Mark
These files have BITPIX = 16, and BZERO = 32768
XnView interprets them as 8bit images, discarding all the negative value pixel information. That is it appears to ignore the BZERO field in the header.
If I understand the standard correctly, when reading a FITs file you should add BZERO (32768 in this case) to every pixel value. For these files this will bring the pixel value range to 0-64k.
The FITs plugin for Photoshop can read these files correctly.
I can supply sample image files if required.
Also the FITS standard does not define the origin of the image and different software packages assume either top-left or bottom-left as the origin resulting in inverted images when reading the same file in different packages. Would it be possible to add the customization of the origin into the XnView configuration?
Mark