Use GIMP Hidden Images for Shadow Removal
There are hidden images in the GIMP layer mode display. There is nothing profound about this, the layer mode presents as a solid color. When a filter is applied to the upper layer, the layer mode interaction changes, and an image appears.
The hidden Divide layer mode image together with Colors-Exposure can produce a very effective shadow removal.
1. Duplicate the image.
2. Use the Divide layer mode.
3. Apply Colors-Exposure to the duplicate.
4. Adjust the sliders to make a preliminary image.
5. Adjust the opacity slider for the layer to complete the procedure.
Like any procedure, this one works on some images, not on others.
To capture a hidden image:
1. Apply the filter of choice but do not click OK.
2. Apply Edit Copy Visible and then Paste As New Layer. This will cancel the filter and the layer image will not be affected.
09-08-2023, 07:16 AM (This post was last modified: 09-08-2023, 07:17 AM by rich2005.)
Yeah, I moved your tutorial post. Providing you do not put in any advertising, put your post here. ( with a title )
You wanted comments. Interesting workflow
3. Apply Colors-Exposure to the duplicate. There is an Exposure filter, is it that one ? Trying that, it tended to be picky leaning to the extreme side. One of the other colour filters might be a better choice and Gimp is great for experimentation.
Like any procedure, this one works on some images, not on others. Very true, I tried various images with mixed results.
As a note, Using the GEGL colour filters, you can apply the mode (Divide) in the filter, opacity as well. There is a split view for comparisons.
Might be an idea to put the two layers in a layer-group. A New-from-Visible will give a new layer of "what you see" without any copy pasting.
This is an [effect = filter + layer mode equation] application that is routinely used. The application can be made with any filter and any layer mode. I found only a few of these applications using “hidden” images, probably because the layer mode images do not present as anything useful. The ones I found are presented in my eBook.
09-08-2023, 10:14 AM (This post was last modified: 09-08-2023, 10:23 AM by PixLab.)
The title needs to be more specific, "GIMP tutorial" has no meaning for me, as it is already a sub-forum.
The right click on a layer while a GEGL or any filter with "preview" is open to have a "New from Visible" is more in description line with the title (yes beginners need to know about it, and that's nice that someone finally speaks about it).
But yeah the title of your post should be something like "New from Visible while a filter with preview is open", thus there is NO hidden image => check the split the view option and you will got a spited view from "new from visible" (using it often I can say I know it well => it's just a "new from visible" which should be in the title, no hidden image)
(09-08-2023, 07:16 AM)rich2005 Wrote: Yeah, I moved your tutorial post. Providing you do not put in any advertising, put your post here. ( with a title )
You wanted comments. Interesting workflow
3. Apply Colors-Exposure to the duplicate. There is an Exposure filter, is it that one ? Trying that, it tended to be picky leaning to the extreme side. One of the other colour filters might be a better choice and Gimp is great for experimentation.
Like any procedure, this one works on some images, not on others. Very true, I tried various images with mixed results.
As a note, Using the GEGL colour filters, you can apply the mode (Divide) in the filter, opacity as well. There is a split view for comparisons.
Might be an idea to put the two layers in a layer-group. A New-from-Visible will give a new layer of "what you see" without any copy pasting.
The procedure is specific to a layer mode. If it was specific to a filter then your approach is indeed one to use.
The method proposed captures the image without applying the filter. The layer is thus available for trial of a different filter. But I need to try out your suggestions.
(09-08-2023, 07:16 AM)rich2005 Wrote: Yeah, I moved your tutorial post. Providing you do not put in any advertising, put your post here. ( with a title )
You wanted comments. Interesting workflow
3. Apply Colors-Exposure to the duplicate. There is an Exposure filter, is it that one ? Trying that, it tended to be picky leaning to the extreme side. One of the other colour filters might be a better choice and Gimp is great for experimentation.
Like any procedure, this one works on some images, not on others. Very true, I tried various images with mixed results.
As a note, Using the GEGL colour filters, you can apply the mode (Divide) in the filter, opacity as well. There is a split view for comparisons.
Might be an idea to put the two layers in a layer-group. A New-from-Visible will give a new layer of "what you see" without any copy pasting.
The procedure is specific to a layer mode. If it was specific to a filter then your approach is indeed one to use.
The method proposed captures the image without applying the filter. The layer is thus available for trial of a different filter. But I need to try out your suggestions.
Wouldn't it be simpler and less risky to just make a copy of the layer first?
I tested a few things to recover shadows (or 'hidden images'). The original photo is underexposed, so I used this one as an example.
- 2x screen mode : used 2 layers with screen mode on the original
- gimp shadows and highlights is the gimp filter under 'Colours'
- divide layer is the workflow from trierwick
- luminosity masks is a plugin from ofnuts (I think), I used the 'M', 'MM' and 'MMM' mask
- the shadow recovery script can be found here: https://www.gimphelp.org/contrast_shadow_recovery.html
09-10-2023, 05:00 PM (This post was last modified: 09-10-2023, 05:04 PM by trlerwick.)
I view procedures as a quiver of arrows you can apply to an image one after another in the hope that one of them will work really well. I will add the procedures that you present to my quiver of arrows.
(09-09-2023, 06:48 AM)Ofnuts Wrote:
(09-08-2023, 02:58 PM)trlerwick Wrote:
(09-08-2023, 07:16 AM)rich2005 Wrote: Yeah, I moved your tutorial post. Providing you do not put in any advertising, put your post here. ( with a title )
You wanted comments. Interesting workflow
3. Apply Colors-Exposure to the duplicate. There is an Exposure filter, is it that one ? Trying that, it tended to be picky leaning to the extreme side. One of the other colour filters might be a better choice and Gimp is great for experimentation.
Like any procedure, this one works on some images, not on others. Very true, I tried various images with mixed results.
As a note, Using the GEGL colour filters, you can apply the mode (Divide) in the filter, opacity as well. There is a split view for comparisons.
Might be an idea to put the two layers in a layer-group. A New-from-Visible will give a new layer of "what you see" without any copy pasting.
The procedure is specific to a layer mode. If it was specific to a filter then your approach is indeed one to use.
The method proposed captures the image without applying the filter. The layer is thus available for trial of a different filter. But I need to try out your suggestions.
Wouldn't it be simpler and less risky to just make a copy of the layer first?
Your layer group approach is the way to go. I don't know why I didn't use it. I do it frequently with Wavelet Decompose.
(09-10-2023, 04:38 PM)denzjos Wrote: I tested a few things to recover shadows (or 'hidden images'). The original photo is underexposed, so I used this one as an example.
- 2x screen mode : used 2 layers with screen mode on the original
- gimp shadows and highlights is the gimp filter under 'Colours'
- divide layer is the workflow from trierwick
- luminosity masks is a plugin from ofnuts (I think), I used the 'M', 'MM' and 'MMM' mask
- the shadow recovery script can be found here: https://www.gimphelp.org/contrast_shadow_recovery.html
If you want to use Luminosity masks to boost shadows you have to use one of the dark masks (DD, likeky). Otherwise the boost occurs on midtones that don't need it.
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