GIMP - TIFF-16 Performance

Software GIMP
1

I haven’t seen any recent posts on this topic …

I usually do some basic processing (exposure, contrast, colour balance, lens corrections, …) in RawTherapee, export as 16-bit TIFF, and then do photo editing in GIMP (v 2.10.38). Most editing actions work fine, but a couple of actions are unusably slow - in particular Rotate and Perspective under Tools / Transform Tools. These work fine with JPEGs, but if I forget and use them with TIFF-16 then I end up having to kill the GIMP task.

Does anyone else have this problem?

Are there any settings I need to make?

The PC is an HP Z4 G4 Workstation, Intel(R) Core™ i9-10920X CPU @ 3.50GHz, with 32GB of RAM. Win 10 Pro, 64bit. Graphics card is a Gigabyte GeForce RTX 2060 SUPER GAMING 8GB.

2

What is the precision of the Image in Gimp (see the title bar) ? Is it 16-bit? If so, use Image > Precision and convert to 32-bit floating point, linear. This is the new native mode in 2.10 so you skip a lot of format conversions.

You can export your image from RT as a 32-bit FP TIFF to get directly the right precision in Gimp.

You can also use Preferences > Image import & export > Import policies > Promote imported images to floating point precision. Caveat: this will apply to all images, and had side effects:

  1. PNG will be exported as 16-bit PNG if you use the default Automatic pixelformat. You can still force the 8-bit format
  2. You cannot export to GIF or even convert to indexed from high precision, you have to convert to 8bit precision first.
3

Wow! I just tried converting the TIFF-16 (yes, it was 16-bit) to 32-point FP, Linear, and that worked as fast as for JPEG. So thanks for that, Ofnuts.

I don’t work with PNG or GIF so I’ll try the Preferences approach as well.

1 Like
4

I know you are using RT and I am not trying to convert you, but darktable offers a xcf file in 32 bit for GIMP which is a great option for users of DT.

5

Trying various things out, the key factor is Floating Point - not whether it’s 16 or 32 bit, or whether it’s Linear or sRGB. So a TIFF 16 Float output from RawTherapee works well. The problem with using Linear (which is applied automatically when you set preferences to promote input files to Floating Point) is that if you output as JPEG, it doesn’t display properly, so you have to change to sRGB before exporting. So my plan going forward is to simply export from RT as TIFF 16 Float. (TIFF 32 Float generates enormous files, and I haven’t found a benefit over 16 bit yet.)