I want to apply mantiuk06 to a really big image¹. However, using the GEGL CLI, I get very different results than when I apply the filter from within gimp as compared to using the GEGL CLI. See attached image: left is original, middle is mantiuk06 applied from within gimp, right is mantiuk06 applied via GEGL CLI.

What is gimp doing differently from GEGL CLI, and is there a way to get the gimp results with the GEGL CLI?

(¹ ...for which I need a custom build, due to https://gitlab.gnome.org/GNOME/gegl/issues/94, and I'd prefer to not have to build my own gimp also.)

Matthew

On 2018-08-09 09:40, Pat David via gimp-user-list wrote:

On Wed, Aug 8, 2018 at 1:46 PM Matthew Woehlke wrote:

I want to apply mantiuk06 to a really big image¹. However, using the GEGL CLI, I get very different results than when I apply the filter from within gimp as compared to using the GEGL CLI. See attached image: left is original, middle is mantiuk06 applied from within gimp, right is mantiuk06 applied via GEGL CLI.

What is gimp doing differently from GEGL CLI, and is there a way to get the gimp results with the GEGL CLI?

(¹ ...for which I need a custom build, due to https://gitlab.gnome.org/GNOME/gegl/issues/94, and I'd prefer to not have to build my own gimp also.)

The list strips images. Could you host he image somewhere and link it?

Well, that seems rather dumb for a list about a graphics program :-). But anyway, as I'd side-tracked the aforementioned related GEGL issue, where I think I also got an answer (still need to check it), the image can be found at
https://gitlab.gnome.org/GNOME/gegl/uploads/e1e40b302523405d10f1234eec1edbeb/roses.png.

Matthew

A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

On 2018-08-07 15:47, Matthew Woehlke via gimp-user-list wrote:

I want to apply mantiuk06 to a really big image. However, using the GEGL CLI, I get very different results than when I apply the filter from within gimp as compared to using the GEGL CLI. See [1]: left is original, middle is mantiuk06 applied from within gimp, right is mantiuk06 applied via GEGL CLI.

What is gimp doing differently from GEGL CLI, and is there a way to get the gimp results with the GEGL CLI?

[1] https://gitlab.gnome.org/GNOME/gegl/uploads/e1e40b302523405d10f1234eec1edbeb/roses.png

To forward Massimo's answer from
https://gitlab.gnome.org/GNOME/gegl/issues/94, it seems gimp (2.8) and GEGL CLI disagree about whether the image is in a linear or gamma-corrected color space, and one is adding an implicit conversion.

While this is an "improvement" for some operations (for mantiuk06, it's hard to argue that the GEGL result isn't more "correct", although stylistically I prefer the "wrong" result in some cases), for many others it ranges from dubiously, to *definitely*, worse. In particular, stress tends to produce a washed-out result. (I mention this mainly because it is my impression that gimp 2.10 behaves the same was as GEGL CLI, though it sounds as if there is an option to control this. PLEASE KEEP THAT OPTION!)

At any rate, the literal answer to my question is:

gegl -o \ cast-format input-format="R'G'B' u8" output-format="RGB u8" \ \
cast-format input-format="RGB u8" output-format="R'G'B' u8"

...which does indeed produce the same results as gimp (2.8). \o/

Matthew