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gimp selection mask plugin
#1
To manipulate part of a photo with multiple masks : https://github.com/edoardogiacomello/gimp-mask

- load a photo
- make a selection
- start the plugin (filters / Light and Shadow / Mask)
- set Number of steps, Desaturation Mode and Apply mask to
- wait for the build of masks
- click on the layers (a white frame appears arround the layer you clicked on) to use curves, levels, hue saturation, etc... (not on the masks !)
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#2
denzjos,

An interesting script which I will have to study! However, there appears to be a problem with the Mid masks - MM, MMM, etc. I suspect this is a result of the error in the original Pat David article as to how to create mid-masks. (This was corrected in the script he produced.)

I have tried a different approach with:



.zip   david2_lum_mask.zip (Size: 2.17 KB / Downloads: 38)

Not so many "bells & whistles", but the masks are non-overlapping so that they can be used individually or in combination. I have also applied equalize to the desaturated image which is used to create the masks so that it works better for low-contrast pictures.

This is all based on the script of Tin Tran and the updated python version which he kindly produced for me.

david.
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#3
The problem is that everyone got intoxicated by the way patdavid builds the masks. His way is very pedagogic, but in real life you don't need to construct the masks by add/substracing/intersecting them(*). You can get your mask directly by applying the adequate curve to the B&W image (aka the "L" mask). This is much faster since you create a single mask directly.

Another shortcoming of following the tutorial is that you end up creating all the masks at once for the initial state of the image (and since this takes some time, and produces a lot of masks, you do it only once). But once you have worked on the image, some pixels may have acquired a new luminosity which is somewhat more (or somewhat less) impacted than their initial luminosity by another mask in the following adjustments.

Which is why I wrote ofn-luminosity-masks that uses Curves to generate arbitrary masks. It will quickly generate one given mask for the current layer. It comes with a bunch of presets (patdavid's masks) but you can add your own, and it also makes it easy to create a mask on the fly by generating a channel from the current layer, on which you can apply any arbitrary curve to select the luminosity range you want.

(*) a clue is the "M" mask, which doesn't select anything fully (max selection level is 50%).
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#4
(12-10-2019, 01:23 PM)Ofnuts Wrote: The problem is that everyone got intoxicated by the way patdavid builds the masks. His way is very pedagogic, but in real life you don't need to construct the masks by add/substracing/intersecting them. You can get your mask directly by applying the adequate curve to the B&W image (aka the "L" mask).

This is what i've been thinking as well.
Making a bunch of luminosity masks seems to unintuitive.
How do you even know which one you want for the effect you had in mind ?

Lets say i want to make a duotone.
I would just duplicate the image, colourize, add the greyscale layermask and then adjust with Curves/Levels until the effect i want appears on the screen.
Who cares if its L, LL, DD, or whatever ?

I know people love their scripts, but this seems not very practical to me.
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#5
I think there is a case for two sorts of luminosity masks. Frequently when adjusting photographs I have found it necessary to make changes in various regions of brightness. For this a set of masks (ideally equally "spaced" and without excessive overlap) are very useful. The appropriate ones can be selected by inspecting the masks.
However, I can also see a need for a mask which can be created interactively, with control of its centre, width and "feather". I believe Darktable already has something of this sort.

david.
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#6
(12-10-2019, 01:46 PM)david Wrote: I think there is a case for two sorts of luminosity masks. Frequently when adjusting photographs I have found it necessary to make changes in various regions of brightness. For this a set of masks (ideally equally "spaced" and without excessive overlap) are very useful. The appropriate ones can be selected by inspecting the masks.
However, I can also see a need for a mask which can be created interactively, with control of its centre, width and "feather". I believe Darktable already has something of this sort.

david.

The best interactive, WYSIWYG way of creating a mask is using Curves. Can you guess what this mask will do:

   
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#7
I just posted the link. I tought it would be interesting for someone. Thanks for the usefull responses.
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#8
What I was looking at was a workflow on photos where one can make more than one selection and change color and contrast independedly from each other (cfr. Nik plugins). This give a nice overview on the whole photo and one can see if one of the changes is not in balance with another. With the suggestions in the posts above, I tried something with a rough selection from the head and one from the dress : 
   
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#9
Ofnuts,

I agree in some respects that the Pat David way of creating masks is somewhat pedantic. (I assume that is the word you meant, as pedagogy is the study of teaching methods!)

Using curves to create masks is something I do very frequently, but when I have an image where I know I am going to use multiple masks, or make a number of hand-drawn masks, I will use the script to produce a set of masks as a starting point.

The script runs in about one second and if some of the masks are not used they have no effect on the result. If finally the image is flattened for export  the masks disappear instantly.

As to the names of the masks, they are only relevant if you wish to communicate with others - selection of masks is done by looking at their thumbnails.

denzjos,

Thanks for posting your link.
I think the best way of producing any result is the way that works for you.

david.
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#10
(12-12-2019, 11:57 AM)david Wrote: I agree in some respects that the Pat David way of creating masks is somewhat pedantic. (I assume that is the word you meant, as pedagogy is the study of teaching methods!)

No, I meant educational/pedagogical...

WhatI do warn about is that most scripts blindly follow Patdavid's tutorial (and Saul Goode's original script) evn though it is  a bit restrictive/counter-productive.
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