[ImageJ-devel] ImageOpener always giving me three channels when these is only one.

Gabriel Landini G.Landini at bham.ac.uk
Mon Dec 13 03:37:55 CST 2010

On Sunday 12 December 2010 22:33:55 Curtis Rueden wrote:
> FYI, ImageJ has a "feature" where if the LUT is totally grayscale, ImageJ
> ignores it and declares the file to be a regular 8-bit image, rather than
> "RGB color." Unfortunately, this makes it difficult to tell if the image has
> a "hidden" color table. Still, you could probably eliminate the LUT by
> resaving as TIFF again from ImageJ.

Just imagine you are working with an 8 bit image, then you want to see some 
contrast enhanced and apply a false colour LUT and then go back to the 
greyscale LUT.
If I saved this image which is now greyscale with the grey.lut, would this be 
re-opened as RGB? Maybe this is not such a good idea.

I do not know how IJ tests the LUT, but I guess it would be trivial: loop 
through the 256 entries and see if they are r=g=b in the expected sequential 
order. If so, then treat as 8bit greyscale image. Checking the table would 
tell you if there are any hidden colours.



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