Post Reply 

Color picker doesn't pick up ONE color

May 30, 2014, 05:14
Post: #1
Color picker doesn't pick up ONE color
Dear all,

In the attached file I have many layers. The color picker works fine on most of them except the layer called "VN Provinces". The color is gray-blue-ish but the color picker always picks up something that's black-blue-ish.

Furthermore, when I fill a space with this color, you can clearly see that it's a different color.
[/align]

Can somebody explain this behavior?
Many thanks!


Attached File(s) Thumbnail(s)
   

.xcf  Map9.xcf (Size: 513.11 KB / Downloads: 19)
Find all posts by this user
Quote this message in a reply
May 30, 2014, 05:47
Post: #2
RE: Color picker doesn't pick up ONE color
the gray-blue is partly transparent, while the black-blue is fully opaque

please visit Gimp-Science-Labs Blog
Visit this user's website Find all posts by this user
Quote this message in a reply
May 30, 2014, 06:13
Post: #3
RE: Color picker doesn't pick up ONE color
Thanks Esper! Where can I see this opacity? Can I copy it to another area / layer?
Find all posts by this user
Quote this message in a reply
May 30, 2014, 06:15
Post: #4
RE: Color picker doesn't pick up ONE color
Using the Color Selection dropper in the Change FG Color dialog will select the color you need.
   
Find all posts by this user
Quote this message in a reply
May 30, 2014, 06:28
Post: #5
RE: Color picker doesn't pick up ONE color
That worked! Thanks!
Just a quick question, how did this "opacity" effect come about? Can I customize it (less/more opacity, remove it completely, etc.)?
Find all posts by this user
Quote this message in a reply
May 30, 2014, 06:30
Post: #6
RE: Color picker doesn't pick up ONE color
(May 30, 2014 06:13)jubinell Wrote:  Thanks Esper! Where can I see this opacity? Can I copy it to another area / layer?
the opacity is at the top of the layers-tab

im not sure how to copy transparency in a color
why would you even wanna do that ?
if you want the same shade as in the semi-transparent colour, i would eye it and get as close as possible

please visit Gimp-Science-Labs Blog
Visit this user's website Find all posts by this user
Quote this message in a reply
May 30, 2014, 06:41
Post: #7
RE: Color picker doesn't pick up ONE color
(May 30, 2014 06:30)Esper Wrote:  Thanks Esper! Where can I see this opacity? Can I copy it to another area / layer?
the opacity is at the top of the layers-tab

But the layer where I have a problem shows an opacity of 100% (!?)
So what's causing the color picker to not pick up the "real" color code?
Find all posts by this user
Quote this message in a reply
May 30, 2014, 06:54 (This post was last modified: May 30, 2014 06:56 by Esper.)
Post: #8
RE: Color picker doesn't pick up ONE color
im not the best person to explain this technical question

transparency is something that is stored in the alpha-channel
opacity is something that changes the transparency of a layer

apparently Gimp hasnt a slider for the alpha channel in the color selector dialog
but when you use the colour-picker and use the info window that you can check in the tool options, it will show you the alpha value

i cant exactly answer your question until you tell me more about your project
you seem to understand what layers are for

so tell me: where does this map come from you are working on ?
and what are you trying to achieve ?

please visit Gimp-Science-Labs Blog
Visit this user's website Find all posts by this user
Quote this message in a reply
May 30, 2014, 07:08
Post: #9
RE: Color picker doesn't pick up ONE color
Thanks Esper. It's a map of Vietnam and the different layers represent things like sea, neighboring countries, labels, etc. that I want to turn on and off at will.

Here, I simply want to understand why when I choose color picker, the color that's picked up is different from what I see with my naked eyes for THIS PARTICULAR layer. I also want to control / change this behavior for future reference. For example, can I turn off this effect completely, to reveal the "true" color (black-blue-ish)?

Thanks!
Find all posts by this user
Quote this message in a reply
May 30, 2014, 07:08
Post: #10
RE: Color picker doesn't pick up ONE color
I'm in agreement with Esper...
The Color Picker tool's info window shows the Alpha value at 30%.
So if you use the darker color the tool selects and fill that color on a separate layer then reduce that layer's opacity to 30% the color will then match. (Remember, as it is now partially transparent the layer's below will effect the final color seen.)
Need to know more on what you are trying to achieve etc.
Adding/Duplicating a 'Channel' is the only place that I recall allows you to specify the opacity of the color you use.
I'm sure another member will have the technical explanation you are seeking.
Find all posts by this user
Quote this message in a reply
May 30, 2014, 07:18
Post: #11
RE: Color picker doesn't pick up ONE color
(May 30, 2014 07:08)jubinell Wrote:  Here, I simply want to understand why when I choose color picker, the color that's picked up is different from what I see with my naked eyes for THIS PARTICULAR layer. I also want to control / change this behavior for future reference. For example, can I turn off this effect completely, to reveal the "true" color (black-blue-ish)?

Thanks!
its possible to change the alpha channel with the levels and curves tool

i still dont understand what you did...
so you copied a map, selected the colours with a selection tool, then used the colour-picker and filled the selection on a new layer with colour ?

(May 30, 2014 07:08)fluffybunny2 Wrote:  I'm sure another member will have the technical explanation you are seeking.
yes, its a very technical question, im sure ofnuts knows the answer

please visit Gimp-Science-Labs Blog
Visit this user's website Find all posts by this user
Quote this message in a reply
May 30, 2014, 07:25
Post: #12
RE: Color picker doesn't pick up ONE color
(May 30, 2014 07:18)Esper Wrote:  i still dont understand what you did...
so you copied a map, selected the colours with a selection tool, then used the colour-picker and filled the selection on a new layer with colour ?
i think i found the answer

tried to replicate what you did
i get semi-transparency when i use the fuzzy select tool
but i dont get semi-transparency when i use the select by colour tool !
it seems you can get the same result with the fuzzy select tool when you uncheck 'Select transparent areas' in the tool options

please visit Gimp-Science-Labs Blog
Visit this user's website Find all posts by this user
Quote this message in a reply
May 30, 2014, 09:45
Post: #13
RE: Color picker doesn't pick up ONE color
Reminder: the color picker has two modes: only pick color from the current layer (in which case the color isn't affected by opacity, local or layer-wide) or pick the color of the result of th eayer composition ("Sample merged" box) where the color picked will be different from the one in the layer if the opacity isn't 100%.

For instance if you have a red layer at 50% opacity over a white background, you get #FF0000 (single layer) or #FF8080 ("Sample merged").

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
May 30, 2014, 19:19 (This post was last modified: May 30, 2014 19:23 by Esper.)
Post: #14
RE: Color picker doesn't pick up ONE color
so to summarise:

transparency = alpha channel
(transparent parts in an image with an alpha channel will be displayed as a gray checkerboard
transparent parts in an image without an alpha channel, will be displayed as white !)

transparency of a layer = opacity

opening an image (png, for example) with transparency does not mean the opacity for the layer will be decreased (it will be 100%)
BUT
if you open an xcf, and one of the layers has a decreased opacity, that is stored in the file

it seems you used the wrong tool for the job
OR
used a wrong tool option

please visit Gimp-Science-Labs Blog
Visit this user's website Find all posts by this user
Quote this message in a reply
May 31, 2014, 00:23
Post: #15
RE: Color picker doesn't pick up ONE color
Thanks for the help guys!
Find all posts by this user
Quote this message in a reply
Post Reply 


Possibly Related Threads...
Thread: Author Replies: Views: Last Post
  Image color vs color picker YalithKBK 1 177 Jul 7, 2017 11:45
Last Post: ythgilb
  Change transparent background color Firion 1 200 Jun 14, 2017 05:24
Last Post: ythgilb
  Blur tool changes the color F_Jenkins17 3 242 Oct 8, 2014 07:38
Last Post: ofnuts
  Color to alpha really weird Sagemode 14 575 Sep 16, 2014 05:49
Last Post: Sagemode
Rainbow How do I save an index image's color map? Zippy0723 1 307 Sep 7, 2014 00:50
Last Post: Zippy0723

Forum Jump:


GIMP ForumPortalArchiveContactTermsRSS