From Newsgroup: comp.graphics.apps.gimp

Hi ,I want to produce a black and white image with just 1 item colour. I
have seen this done so I know there is software capable of it.

So,question 1 can GIMP do this ?

Question 2 if so how ? Point me in the right direction please .I don't
even know what to search for.

I'm using GIMP 2.10.22 x64
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From Newsgroup: comp.graphics.apps.gimp

On 2020-10-16, grinch <grinch@somewhere.com> wrote:

Hi ,I want to produce a black and white image with just 1 item colour. I have seen this done so I know there is software capable of it.

black and white is already two colours. Do you mean you want a three
colour image? To get a one colour image is easy-- just produce an all
white image (erase everything). I think you are not giving enough
information of what you want to do. Are you creating this image? Ar yo manipulating some image someone has given you?

So,question 1 can GIMP do this ?

Do what?

Question 2 if so how ? Point me in the right direction please .I don't
even know what to search for.

I'm using GIMP 2.10.22 x64

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From Newsgroup: comp.graphics.apps.gimp

On 16/10/2020 17:01, Arthur T. wrote:

In Message-ID:<rmbslo$15ba$1@gioia.aioe.org>,
grinch <grinch@somewhere.com> wrote:

Hi ,I want to produce a black and white image with just 1 item colour. I
have seen this done so I know there is software capable of it.

It depends on where you're starting from.

If you're starting with a full-color picture, select the one item you
want to keep (either of the select-by-color tools, smart scissors, or whatever other method). Invert the selection so you've selected
everything else. Then desaturate. That will get rid of all colors in
the now-selected areas.

If you meant keeping one color regardless of how many items it's in,
use the "Select by color" tool rather than the magic wand, and use
settings wide enough to capture all of the areas you want.

Thank you Sir that worked perfectly. I have not used GIMP in quite a
while.I will save your instructions for the next time.
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From Newsgroup: comp.graphics.apps.gimp

On 16/10/2020 18:26, William Unruh wrote:

black and white is already two colours. Do you mean you want a three
colour image? To get a one colour image is easy-- just produce an all
white image (erase everything). I think you are not giving enough
information of what you want to do. Are you creating this image? Ar yo manipulating some image someone has given you?

This is Adobe's description of Black and White:-
"Black is the absence of light. Unlike white and other hues, pure black can exist in nature without any light at all. Some consider white to be a color, because white light comprises all hues on the visible light spectrum. ...
But in a technical sense, black and white are not colors, they're shades".
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From Newsgroup: comp.graphics.apps.gimp

On 2020-10-17, David Lawrence <David_Lawrence@example.net> wrote:

On 16/10/2020 18:26, William Unruh wrote:

black and white is already two colours. Do you mean you want a three
colour image? To get a one colour image is easy-- just produce an all
white image (erase everything). I think you are not giving enough
information of what you want to do. Are you creating this image? Ar yo
manipulating some image someone has given you?

This is Adobe's description of Black and White:-
"Black is the absence of light. Unlike white and other hues, pure black can exist in nature without any light at all. Some consider white to be a color, because white light comprises all hues on the visible light spectrum. ... But in a technical sense, black and white are not colors, they're shades".

On a computer both black and white are colours. Black has RGB of all 0,
and white has RGB of all bits 1. Other colours are mixtures of 0 and 1.
Since you are talking about computers, it is their definition of colour
that is relevant, not some philosphical discussion of "what is colour".
All colours are shades, that that distinction is pretty useless.
It does seem that he wanted three colours, black white and some third
colour.
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From Newsgroup: comp.graphics.apps.gimp

On Fri, 16 Oct 2020 21:45:41 +0100, grinch <grinch@somewhere.com>
wrote:

On 16/10/2020 17:01, Arthur T. wrote:

In Message-ID:<rmbslo$15ba$1@gioia.aioe.org>,
grinch <grinch@somewhere.com> wrote:

Hi ,I want to produce a black and white image with just 1 item colour. I >>> have seen this done so I know there is software capable of it.

It depends on where you're starting from.

If you're starting with a full-color picture, select the one item you
want to keep (either of the select-by-color tools, smart scissors, or
whatever other method). Invert the selection so you've selected
everything else. Then desaturate. That will get rid of all colors in
the now-selected areas.

If you meant keeping one color regardless of how many items it's in,
use the "Select by color" tool rather than the magic wand, and use
settings wide enough to capture all of the areas you want.

Thank you Sir that worked perfectly. I have not used GIMP in quite a
while.I will save your instructions for the next time.

I guess you got what you wanted, but there is another method that I
would like you to try -- it means learning something about layers and
layer masks. The reason is that I find it easier to fix a selection
made by masking than those obtrained by selecting only. The
'only' is important - you can do some rough masking by using
selection tools, like the lasso, tool, but refine it by the mask to
get just what you want to isolate.

1. Create a copy of your colour image in a new layer and desaturate
it. This will provide the B&W portion of what you are looking for. Put
it *above* the colour layer (i.e. the original picutre). All you will
see now is the desaturated B&W picture.

2. Add a layer mask to the upper (desaturated layer) with full
opacity (white). All you will still see is full desaturated image.

3. Now selcted a hard brush, and start to paint full black
*in the layer mask* in those regions you want to have colour.
As you paint black (in the mask!), you will see the lower, full colour
layer appear in the painted regions.

The reason I like this is that any errors you make can be easily
fixed - simply paint full white in the mask the regions you
want to correct, swtich colour to black and start to 'expose'
the lower full colour layer.
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