Gimp-Forum.net › GIMP › General questions
Posterize or make contour lines by defined colours

Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Thread Modes
Posterize or make contour lines by defined colours
pygmalion Offline
Junior Gimper
**
Posts: 9
Threads: 3
Joined: Apr 2020
Reputation: 0
Operating system(s):
  • Windows (Vista and later)

Gimp version: 2.8
#1
06-19-2020, 10:15 AM
I have a picture as a result of a calculation program:

[Image: IOjSA6I.png]

There is also a legend for values:

[Image: Xtqyo2l.png]

Now, I would like to make a picture with seven colours (posterize) OR find six isocolor lines.  The six threshold colours can be extracted from the legend with equidistance.

Is something like that even possible in GIMP?  When I make posterize in GIMP it does the job but I don't like the colours that were automatically selected as threshold colours
Find
Reply
denzjos Offline
Gimper extraordinaire
***
Posts: 1,136
Threads: 177
Joined: Sep 2018
Reputation: 113
Operating system(s):
  • Windows (Vista and later)

Gimp version: 2.10
#2
06-19-2020, 11:56 AM (This post was last modified: 06-19-2020, 11:58 AM by denzjos.)
Maybe this is a solution :
GMicQt / Artistic / Cutout 
Number of levels 7
Edge Simplicity 3
Edge Fidelity 2

   
Find
Reply
pygmalion Offline
Junior Gimper
**
Posts: 9
Threads: 3
Joined: Apr 2020
Reputation: 0
Operating system(s):
  • Windows (Vista and later)

Gimp version: 2.8
#3
06-19-2020, 03:44 PM (This post was last modified: 06-19-2020, 03:45 PM by pygmalion.)
(06-19-2020, 11:56 AM)denzjos Wrote: Maybe this is a solution :
GMicQt / Artistic / Cutout 
Number of levels 7
Edge Simplicity 3
Edge Fidelity 2

Unfortunately, this tool takes wrong threshold colors.  I think that threshold colors must be picked manually.  But how?
Find
Reply
Ofnuts Offline
Administrator
*****
Posts: 6,324
Threads: 271
Joined: Oct 2016
Reputation: 561
Operating system(s):
  • Linux

Gimp version: 2.10
#4
06-19-2020, 04:50 PM
(06-19-2020, 03:44 PM)pygmalion Wrote:
(06-19-2020, 11:56 AM)denzjos Wrote: Maybe this is a solution :
GMicQt / Artistic / Cutout 
Number of levels 7
Edge Simplicity 3
Edge Fidelity 2

Unfortunately, this tool takes wrong threshold colors.  I think that threshold colors must be picked manually.  But how?

Create a palette with the color you want, and use Image>Mode>Indexed and specify your palette as a custom palette. If necessary, copy the graphic to its own image and color-index it, and copy-paste the result in the initial image.
Find
Reply
rich2005 Offline
Administrator
*****
Posts: 7,123
Threads: 155
Joined: Oct 2016
Reputation: 1,003
Operating system(s):
  • Linux

Gimp version: 2.10
#5
06-19-2020, 05:13 PM
Again using indexed mode, slightly different to above:
------------------
Not much you can do with that image. First lose the border, It does not help. You can put it back later.

Screenshots for reference - all in Gimp 2.8 https://i.imgur.com/yGbbi5O.jpg

1. Convert to indexed mode with 6 colours. Image -> Mode -> Indexed

that gets just 6 colours but the border are a bit 'jagged'

2. Back to RBG mode Image -> Mode RGB the apply a Gauusian blur - quite strong about 20

3. Repeat stage 1 Image -> Mode -> Indexed with 6 colours. That smooths the borders a bit. If you want to change any of the colours, edit the colormap

Then if you need to back to RGB mode, you will still have just 6 colours.

I did look around for suitable scripts or plugins but nothing much different to changing the colour mode
Find
Reply


Forum Jump: