Found solution for Opening JPF (JPEG2000) files

[DeepDesertPhoto]

About a month or so ago I posted a topic asking when APh was going to add JPF (JPEG2000) support.

During the discussion I was told by several forum members that they were able to open files with extensions of JP2.
However, all of my old JPEG2000 files had the extension of .JPF and I kept getting an error that this file type was not supported.
This was most likely due to the JPF extension being only used by Photoshop.
A couple of members pointed me in the direction of other programs and online services that would do the job but I found those programs cumbersome to use and I did not like doing online conversions since image theft is rampant on the internet.

After much searching I finally found one program that is free and will open older Photoshop JPF files.
It is called GIMP.
Many of you probably know about it.
In the past GIMP only supported 8 bit color depth, but in their newest release, version 2.10.14, they have now added 16 and 32 bit color depth support. They also added support for what they referred to as "Rare Formats".
They did not state JPF specifically but I decided to take a chance and download the program.

To my relief GIMP was able to open my older JPF files if they were already in RGB mode.
Because GIMP does not support LAB color I had to use my Mac's Preview App to convert the JPFs that were in LAB to JP2 RGB.
I then opened the JP2s produced by Preview App with GIMP and exported them to 16 bit RGB TIFF.
The only thing I had to do before converting the JPF to TIFF was change the display resolution from the GIMP default of 72PPI to 300PPI so that the resulting TIFF would be at 300PPI.

After the conversion using GIMP I was then able to open the new TIFF file with Affinity Photo and simply convert it back to LAB color before saving it to replace the original JPF version.

Just thought I would alert all of you that there is now a free solution to the conversion of older JPFs in case any of you still have files in that older format.

On an additional note about the conversion, if you have to use the Preview App to convert a JPF to JP2 set it for lossless to preserve all the original quality.
I know that Affinity Photo can open JP2, but when I tried that the colors displayed were over saturated.
I also tried using the Preview App to convert the JPFs that were in LAB color directly to TIFF but the Preview App would not give me a 16 bit option and the result was duller colors.
By using GIMP to convert the JP2 to 16 bit TIFF the color saturation stayed original.
 

Edited December 9, 2019 by DeepDesertPhoto
clarification and correction