Re: [Gimp-user] Problems with changing layer mode in scheme

[Pat David <patdavid gmail com>]

I'm not near my machine to test your script (but can have a look tomorrow).
In the meantime, have you seen the tutorial on doing Luminosity masks?

https://www.gimp.org/tutorials/Luminosity_Masks/
On Tue, Apr 18, 2017 at 6:31 PM Ken Moffat <zarniwhoop ntlworld com> wrote:

> Hi,
>
> sorry for the long intro, but I tend to believe that context is
> important.
>
> When I have the time, I'm gradually trying to 'process' raw photos
> I've taken in the past.  A brief overview is: select a base exposure
> and two others for shadows and highlights (typically ±2EV), put
> those in layers with masks, remove the masks, merge down.  After
> that I do visual correction (lens distortion, rotation, perspective
> distortion) and then things like tone mapping and sharpenbing.
>
> I got back to this a few monbths ago and discovered that although
> it sounds obvious to use the base image ("correct exposure") to
> create the masks - i.e. what is dark in that, rather than in the
> overexposed shadow layer, should be retrieved from the shadow layer,
> and vice versa - I got horrible results.  Eventually I found out
> about "lighten only" and "darken only" layer modes.
>
> So, I now have enough confidence in that approach to try using it.
> But I still need to make decisions about which exposures to use, and
> what other things to do, so each picture still takes a long time.
> But the "merge three exposures" part is one of hte slowest parts of
> hte process and is more likely to work well when scripted: from time
> to time I do something wrong when I do it manually.
>
> I found load_for_hdr_0.scm which appears to be doing similar things
> to what I want to do, so I've been trying to hack on it.  This is
> with gimp-2.8.20, I'll give it a go in my machine running once it
> seems to work.  Hmm, for those of us without a CS background,
> scheme/lisp is hard.  I've been trying to set the layer mode in the
> appropriate part of my fork of that script.
>
> It started out before my changes as -
>
> (define (process-single-image
>                 dest-image
>                 source-image
>                 dest-layer-name
>                 desaturate-option
>                 invert-option
>                 blur-radius)
>     (let* (
>             (layer (copy-image-as-new-layer dest-image source-image)))
>
>     (gimp-layer-set-name layer dest-layer-name)
>     (gimp-desaturate-full (car (gimp-image-get-active-drawable
> source-image)) desaturate-option)
> ...
>
> First I tried adding dest-layer-mode after dest-layer-name in the
> definitions, and passing LIGHTEN-ONLY-MODE (that is, 10) after the
> layer name, then adding
>
>     (gimp-layer-set-mode layer dest-layer-mode)
>
> after gimp-layer-set-name, but I got an error from the following
> gimp-desaturate-full :
>
> Error: ( : 1) Procedure execution of gimp-desaturate-full failed on
> invalid input arguments: Procedure 'gimp-desaturate-full' has been
> called with value '10' for argument 'desaturate-mode' (#2, type
> GimpDesaturateMode). This value is out of range.
>
> That puzzles me, the parameters were in order, but I tried to work
> around it by moving dest-layer-mode to the last parameter, after
> blur-radius.  That ran without error, but the added layers are still
> in normal mode. :-(
>
> I'm also at a loss about how to debug this - the examples I can find
> are all pretty short, this script (ignoring comments) is all-but 100
> lines, and I don't seem to be able to paste into the script-fu
> window (running xfce on this machine).
>
> Any suggestions, please ? (Other than using Python - I prefer to
> build from source, the impenetrable deps in some Python scripts
> annoy me, and taking a quick look at two very-long Python scripts
> which appear to be for this sort of use I found their code totally
> impenetrable, and they did not come close to doing what I wanted).
>
> ĸen
> --
> `I shall take my mountains', said Lu-Tze. `The climate will be good
> for them.'     -- Small Gods
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