I have been scouring these forums and the Google for a few days now to see if I could figure this out on my own… but to no avail. I hope this hasn’t been answered elsewhere, but I could sure use some help!
So, what I’ve been trying to do is to add film grain to a bunch of images at once instead of opening each file in GIMP, applying the filter, then saving. Thats when I decided to dive head first into gmic’s CLI. And now I am fully in the rabbit hole.
The command I am using is
-fx_simulate_grain 0,1,0.286,100,0,-0.2,0,-2,0,0,0,0 which I found out how to write using verbose mode (layer name) in the GIMP G’mic Plugin. Fiddling around with the settings, the string of numbers should represent the:
- “Orwo NP20-GDR” grain type
- Grain Merge Blend mode
- Opacity at 0.286
- Scale at 100
- Colored Grain NOT checked
- Brightness at -0.2
- Contrast at 0
- Gamma at -2
- Hue, Saturation, and the rest at 0
Using this on a lower bit image like a png works fine.
$ gmic image.png -fx_simulate_grain 0,1,0.286,100,0,-0.2,0,-2,0,0,0,0 -o output.png
That even outputs an image that looks like the input (oooowweeee that was hard figuring that out, and yes I still have questions on it) with the grain added.
But when I attempt to use a 32 bit float tiff that I have exported from RawTherapee, most of the blend modes end up producing just grain against a black background.
$ gmic image.tif -fx_simulate_grain 0,1,0.286,100,0,-0.2,0,-2,0,0,0,0 -n 0,65535 -o output.tif,ushort
This puts out a black background splattered with small dots. Yet if I change the blend mode setting to 3, 4, or 5 it works like its supposed to (with 5 it’s just grain only).
I am running Gmic 2.8.4 that I downloaded from aferrero2707 and have ran
$ gmic update, on a Macbook Pro Retina late 2012 running osx 10.12.6 (I know its old, but at least this version supports the supplied graphics card)
Here are some links to let you experiment:
The Grain settings are in the files name. Thank you all sooooooooo much for your help!! If you need anymore info from me let me know.
And as a side note,
-n 0,65535 -o output.tif,ushort still doesn’t quite save a 32bit float tiff image how I would see it if I opened it up in GIMP or RawTherapee. Any help there would be great too!