Exchanging Colours

[pipp44]

I have a CAD programme, I would like to recolour the GUI to submit to the company as a suggestion for a new colour scheme.

My question is : Is it possible to "sample" a particular colour on the GUI and then ask GIMP to recoulor all of that selected colour to the colour that I want to change it to ?

At the moment the only way I can think of would be to draw rectangles, ellipses, circles etc and then use the bucket tool to fill in the drawn rectangles etc.

Thanks in advance

[Blighty]

Try the Colour Select Tool. In the Tool Options, experiment with Threshold values.

Also in the Tool Options there are 4 Modes. Replace, Add, Subtract, Intersect. You will probably need these too.

[Ofnuts]

Add a layer over the image, set it in Color or Hue mode (selector at top of Layers list). Paint over it to change the color of what is below.

• Painting doesn't need to be accurate (with some luck you can fill the layer).
  
• Tranaprency on the top layer leaves the bottom layer unchanged
  
• In any case it is easier to fix that painting directly in on the initial image (make the top layer transparent where you want to redo from the initial image).
  

See attached XCF for an example.


  ChangeColors.xcf (Size: 135.77 KB / Downloads: 349)

[Espermaschine]

(08-03-2018, 01:48 PM)Ofnuts Wrote: Add a layer over the image, set it in Color or Hue mode (selector at top of Layers list). Paint over it to change the color of what is below.

Nice trick !

Can be extended by putting another black layer on top of the stack and set it to 'Saturation'.
This way you can manipulate the Hue with the Hue "adjustment" layer, and adjust the saturation with the Saturation "adjustment" layer.

[pipp44]

(08-03-2018, 01:48 PM)Ofnuts Wrote: Add a layer over the image, set it in Color or Hue mode (selector at top of Layers list). Paint over it to change the color of what is below.

• Painting doesn't need to be accurate (with some luck you can fill the layer).
  
• Tranaprency on the top layer leaves the bottom layer unchanged
  
• In any case it is easier to fix that painting directly in on the initial image (make the top layer transparent where you want to redo from the initial image).
  

See attached XCF for an example.

Hi Ofnuts.
I looked at the example that you put in and that is exactly what I am after, I am not that great with GIMP yet, and not sure what you did and not sure of what to do myself, any chance of a bit of a tutorial ?

UPDATE:
              I played around a little bit, and looked on Youtube and found a couple of videos that show this technique, I got the jist of what to do, but I am not getting the colour that I choose, I am trying to make the menus of the programme a dark grey, I have the colour set to that colour, but when I paint the image the colour is like a washed out pink colour.
When I hide the screenshot layer, the new layer shows the painted line in the colour I want but its not showing in the screenshot layer.
What am I missing?
T I A .

[Ofnuts]

(08-04-2018, 05:41 AM)pipp44 Wrote:

(08-03-2018, 01:48 PM)Ofnuts Wrote: Add a layer over the image, set it in Color or Hue mode (selector at top of Layers list). Paint over it to change the color of what is below.

• Painting doesn't need to be accurate (with some luck you can fill the layer).
  
• Tranaprency on the top layer leaves the bottom layer unchanged
  
• In any case it is easier to fix that painting directly in on the initial image (make the top layer transparent where you want to redo from the initial image).
  

See attached XCF for an example.

Hi Ofnuts.
I looked at the example that you put in and that is exactly what I am after, I am not that great with GIMP yet, and not sure what you did and not sure of what to do myself, any chance of a bit of a tutorial ?

UPDATE:
              I played around a little bit, and looked on Youtube and found a couple of videos that show this technique, I got the jist of what to do, but I am not getting the colour that I choose, I am trying to make the menus of the programme a dark grey, I have the colour set to that colour, but when I paint the image the colour is like a washed out pink colour.
When I hide the screenshot layer, the new layer shows the painted line in the colour I want but its not showing in the screenshot layer.
What am I missing?
T I A .

These layers modes work in the HSV model: in that model the color is not expressed as a mix of R, G, B, but as a Hue, a Saturation level (no saturation: black/gray/white) and a Value (luminosity, more or less). When you paint in the top layer which  is in Color mode, the composition takes the Hue and Color from what you paint and keeps the Level from the bottom. Of course, if you paint in gray, there is no saturation and the Hue isn't even very well defined. In your case you don't want to change the color, you want to remove it.

Something you can do is use "Saturation" mode and paint with a color with not saturation (ie, gray).

[pipp44]

(08-04-2018, 12:31 PM)Ofnuts Wrote:

(08-04-2018, 05:41 AM)pipp44 Wrote:

(08-03-2018, 01:48 PM)Ofnuts Wrote: Add a layer over the image, set it in Color or Hue mode (selector at top of Layers list). Paint over it to change the color of what is below.

• Painting doesn't need to be accurate (with some luck you can fill the layer).
  
• Tranaprency on the top layer leaves the bottom layer unchanged
  
• In any case it is easier to fix that painting directly in on the initial image (make the top layer transparent where you want to redo from the initial image).
  

See attached XCF for an example.

Hi Ofnuts.
I looked at the example that you put in and that is exactly what I am after, I am not that great with GIMP yet, and not sure what you did and not sure of what to do myself, any chance of a bit of a tutorial ?

UPDATE:
              I played around a little bit, and looked on Youtube and found a couple of videos that show this technique, I got the jist of what to do, but I am not getting the colour that I choose, I am trying to make the menus of the programme a dark grey, I have the colour set to that colour, but when I paint the image the colour is like a washed out pink colour.
When I hide the screenshot layer, the new layer shows the painted line in the colour I want but its not showing in the screenshot layer.
What am I missing?
T I A .

These layers modes work in the HSV model: in that model the color is not expressed as a mix of R, G, B, but as a Hue, a Saturation level (no saturation: black/gray/white) and a Value (luminosity, more or less). When you paint in the top layer which  is in Color mode, the composition takes the Hue and Color from what you paint and keeps the Level from the bottom. Of course, if you paint in gray, there is no saturation and the Hue isn't even very well defined. In your case you don't want to change the color, you want to remove it.

Something you can do is use "Saturation" mode and paint with a color with not saturation (ie, gray).

Hi Ofnuts.

 I think I will give it a miss, I have no idea what I am doing (truth be known, not enough experience with GIMP so don'y understand a lot of it) and I don't want to waste your or this forums time with what looks like basic stuff that I should know.

thank again

[Ofnuts]

The purpose of this forum is mostly to explain basic stuff

[pipp44]

(08-05-2018, 09:46 AM)Ofnuts Wrote: The purpose of this forum is mostly to explain basic stuff

Ok thank you.
Is there an explanation somewhere or a tutorial of what you were talking about regarding the Saturation, HSV etc.
 Just to satisfy my curiosity I opened up Krita and tried it in there and got the exact same result ( shows I don't know enough about Krita either ) ,   I cannot get the grey to paint where I want it, I keep getting the washed out colour and the grey colour I want is only on the new layer.

[Ofnuts]

https://en.wikipedia.org/wiki/HSL_and_HS..._principle

(don't be afraid by the rest of the article... yo only need the paragraph I link to).