Re: [Gimp-user] Image luminosity

[Richard]

Another option that might work is luma.  This can be easily determined by 
converting the image to grayscale, or decomposing the color channels using a 
YCbCr color model (yielding one layer for luma, and two layers for chroma).


-- Stratadrake
strata_ran...@hotmail.com

Numbers may not lie, but neither do they tell the whole truth.

From: gimp-user-list  on behalf of Elle Stone 

Sent: Saturday, March 10, 2018 6:47:53 AM
To: gimp-user-list@gnome.org
Subject: Re: [Gimp-user] Image luminosity

On 03/10/2018 03:55 AM, Ofnuts wrote:
> On 03/07/18 15:10, WMusc wrote:
>>> Something like:
>>>
>>> Color>Desaturate (luminosity) and check the average or median in the
>>> Histogram dialog.
>> Thanks for the tip. Do you know whether that approach provides the
>> mean (median,
>> etc.) luminosity value before or after desaturation? It looks to apply
>> the
>> effect so it's unclear to me. If the program applies it uniformly
>> across all
>> images I may be able to use it as a proxy for luminosity but would
>> like to avoid
>> that if possible.
>>
> I expect Color>Desaturate>Luminosity to not change the luminosity of the
> pixel. The grey value after is normally the luminosity you would have
> computed from the RGB components you have in the initial image.
>
> This said, in 2018 I'm surprised you are engaging in such manual labor.
> Find someone (intern?) to write a small program that will extract all
> these data directly from the image files and create a spreadsheet with
> the results.

Before finding an intern to write a program, it might be a good idea to
figure out whether the metrics you've decided to extract are actually
useful to the task at hand. Garbage in/garbage out, as I've been trying
to say over in the pixls.us thread on this topic:
https://discuss.pixls.us/t/image-luminosity/6904

As far as extracting information from an image, ImageMagick might be a
better choice than GIMP - more available metrics, though again it's an
open question as to whether any of the metrics actually help you decide
whether an image is "too this" or "not enough that". Remember the red
square in the middle of an otherwise solid gray image that I posted to
the pixls.us thread - the relative luminance of the red square is
exactly the same as the relative luminance of the background, but I'm
fairly sure just about everyone will say the red square is "brighter",
as indeed it according to the definition of "brightness" used in current
color appearance models.


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Re: [Gimp-user] Any way to resize all the layers in an xcf file to fit the canvas?

[Ofnuts]

On 03/11/18 21:57, Ofnuts wrote:

On 03/11/18 15:21, Elle Stone wrote:

Hi All,

Of course all the layers can be resized one by one to fit the canvas. 
But I've been doing a *lot* of rearranging/moving of different groups 
of layers, and clicking on each layer one by one to resize it is 
rather time-consuming and involves a lot of clicking. Right now 
that's 17 layers and four groups.


Is there a magic command, or maybe an easy script that can be run to 
resize all the layers to fit the canvas, all at once?


Also, does the layer mask resize when the layer is resized?

In case it matters, I'm using GIMP 2.9.8 on Linux.

Best,
Elle



My trick for this (on 2.8):

- Image>Canvas size and add 1 px, and select "resize all layers"

- Image>Canvas size and remove 1 px, and select "resize all layers"

Otherwise, in the python console:

    image=image=gimp.image_list()[0] # or other ways to obtain image

    for layer in image.layers: layer.resize_to_image_size()

(strike [enter] twice)


Since I have sen this question asked many times, I made a short script 
out of it:


See ofn-layers-to-image-size at 
https://sourceforge.net/projects/gimp-tools/files/scripts/


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Re: [Gimp-user] Any way to resize all the layers in an xcf file to fit the canvas?

[Ofnuts]

On 03/11/18 15:21, Elle Stone wrote:

Hi All,

Of course all the layers can be resized one by one to fit the canvas. 
But I've been doing a *lot* of rearranging/moving of different groups 
of layers, and clicking on each layer one by one to resize it is 
rather time-consuming and involves a lot of clicking. Right now that's 
17 layers and four groups.


Is there a magic command, or maybe an easy script that can be run to 
resize all the layers to fit the canvas, all at once?


Also, does the layer mask resize when the layer is resized?

In case it matters, I'm using GIMP 2.9.8 on Linux.

Best,
Elle



My trick for this (on 2.8):

- Image>Canvas size and add 1 px, and select "resize all layers"

- Image>Canvas size and remove 1 px, and select "resize all layers"

Otherwise, in the python console:

    image=image=gimp.image_list()[0] # or other ways to obtain image

    for layer in image.layers: layer.resize_to_image_size()

(strike [enter] twice)

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[Gimp-user] Please Help 2.8.22 File>Open Not Working Properly

[Laura Pryor]

Hello. I bet someone knows how to fix this. Can you help? I installed 2.8.22 
about a week ago and am struggling with the File>Open command. Instead of 
opening the file I want to work with in an additional window, this command 
opens a second running GIMP program.

This also happens if I navigate to a file, right click and use the Open With 
command.

If someone can help me that'd be so great! I've done some research and have 
only found people with similar instances but not a fix.

Thank you so much!

Laura
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Re: [Gimp-user] Any way to resize all the layers in an xcf file to fit the canvas?

[Carol Spears]

On Sun, Mar 11, 2018 at 10:21 AM, Elle Stone  wrote:

> Hi All,
>
> Of course all the layers can be resized one by one to fit the canvas. But
> I've been doing a *lot* of rearranging/moving of different groups of
> layers, and clicking on each layer one by one to resize it is rather
> time-consuming and involves a lot of clicking. Right now that's 17 layers
> and four groups.
>
> Is there a magic command, or maybe an easy script that can be run to
> resize all the layers to fit the canvas, all at once?
>
It is much much easier to resize the canvas to fit all of the layers.


>
> Also, does the layer mask resize when the layer is resized?
>
I just tried this and it does.  You can try this also, Edit -->Undo is a
friend

carol
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[Gimp-user] Any way to resize all the layers in an xcf file to fit the canvas?

[Elle Stone]

Hi All,

Of course all the layers can be resized one by one to fit the canvas. 
But I've been doing a *lot* of rearranging/moving of different groups of 
layers, and clicking on each layer one by one to resize it is rather 
time-consuming and involves a lot of clicking. Right now that's 17 
layers and four groups.


Is there a magic command, or maybe an easy script that can be run to 
resize all the layers to fit the canvas, all at once?


Also, does the layer mask resize when the layer is resized?

In case it matters, I'm using GIMP 2.9.8 on Linux.

Best,
Elle
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