How to pick color of paper?

[ajax]

The color profiles for paper to be used when printing are available to GIMP.  It seems that when editing an image it should be possible to choose (?color picker) a color that corresponds to photo paper that could end up being used to print the subject image.  How can that be done?

[Ofnuts]

The image saved by Gimp doesn't depend on the intended printer. But a printer would have different color profiles to match the papers used.

[rich2005]

Guessing you mean the printer/paper icc profile rather than just printing on (say) pink paper

Set the paper proflle up in Preferences Colour Management for soft proofing: https://imgur.com/EyXBY2z.jpg

There is in addition a section in the view menu.: https://imgur.com/NDfX2iN.jpg

Unless your monitor is colour profiled, you might not see much difference, out-of-gamut will show which might help (as a warning)

High quality printing is tough subject. A good source of info is http://www.cambridgeincolour.com

[ajax]

(06-03-2019, 04:56 PM)rich2005 Wrote: Guessing you mean the printer/paper icc profile rather than just printing on (say) pink paper

Set the paper proflle up in Preferences Colour Management for soft proofing:    https://imgur.com/EyXBY2z.jpg

There is in addition a section in the view menu.:  https://imgur.com/NDfX2iN.jpg

Unless your monitor is colour profiled, you might not see much difference, out-of-gamut will show which might help (as a warning)

High quality printing is tough subject. A good source of info is http://www.cambridgeincolour.com

Yes!  The basic idea is that if I want to add something to an image that is white, for example text or border, I'd like the printer to choose the color of the paper rather than try to print a different tone of white.

I do realize that different kinds of photo paper have different ICC profiles but since I have those installed and use them for soft proofing it seems like I should be able to set the color, for example background color, in GIMP to match the paper.

My display is calibrated but I'm not really worried, too much, about what I see on the display it is what gets done to the paper that I'm thinking about.

Possibly by just setting the color to absolute white (i.e., FFFFFF), which should be out of gamut for whatever paper I might use, the printer will opt NOT to try and print anything.  In that, the plan (NOT printed) paper is as close as it can get.  I'm unsure what the printer will do but I suppose this amounts to being a question about the printer rather than the editing software.

My thought is that if I can set the color to the color of the paper then when I soft proof I should get a pretty good idea of what the printed picture will look like.

What might be different about me is that any picture worth making the effort to do custom development is something I do intend to print.  I have a fairly good photo printer which includes explicit color profiles for lots of different papers.  Obviously this would put me in need of choosing the target paper when the image is being created.

[rich2005]

Oh.. you do want to use coloured (off white? ) paper.

On the basis that there is (usually) no white ink used in CMYK printing ane white = no ink / transparent

Remove the white component from the image. Add alpha channel to image / color-to-alpha using white as the colour.

Gives something like this: https://imgur.com/uRCZqM0.jpg

For a print simulation put a colour layer under. example using pink https://imgur.com/66ivHG2.jpg Might not be exact, printing is complex procedure.

[ajax]

(06-04-2019, 07:11 AM)rich2005 Wrote: ...
On the basis that there is (usually) no white ink used in CMYK printing ane white = no ink / transparent
...

This thought looks to be what I had in mind with idea of "absolute" white.  While I realize that the printer cannot print real white the question becomes how far "off white" must it be before the printer starts applying ink/pigment?

(06-04-2019, 07:11 AM)rich2005 Wrote: ...
Remove the white component  from the image.  Add alpha channel  to image / color-to-alpha using white as the colour.
...

I must admit that alpha channels are something I don't really understand but things such as text and borders are being done by adding layers.  However, as you say "printing is complex procedure" which is the explanation I might use to explain that it is something that GIMP does poorly if at all.  Therefore, these images need to be rendered into a standard image format, in my case .tif, that can be opened by other software for the purpose of printing.  At this point those white areas are as much a part of the image as anything else.  Aren't they?

[rich2005]

Quote:...At this point those white areas are as much a part of the image as anything else. Aren't they?

Not when printed. As before there is no white ink.

White = colour of the paper.

How far off-white before there is a tint. Probably not very much. I will let you do the trials.

--------------
Ok before I pack in for the night. This is how I might do a simulation of a print on an off-white paper.

Using Color-to-Alpha, pick the opacity threshold from the image to get as close to original as possible. https://imgur.com/8Uvds0W.jpg

An underlay with the 'proposed' paper color. https://imgur.com/YgXEn3B.jpg

Flatten the image. Using the colour picker tool and the info window check a white area. https://imgur.com/5ThRBgn.jpg

How much of the colours are used? A smattering of red & green and a bit more of blue. But this is a RGB image, once it gets translated by the printer to CMYK then expect some change.

[ajax]

You've kind of forced me to spend some time learning about alpha channel.  While I've got more work to do on that score one thing I've learned, which I didn't know previously, is that some image file formats support them.  This means they are not confined to GIMP, or other editing software, as I was previously thinking.  Rather, GIMP can create standard image files that contain them.

Insofar as my interest had to do with things I'd be adding to the image, text and borders, I'm thinking this means that I could use an alpha channel to create these things as transparent which would then cause them to be whatever the color of the paper on which they are printed.  However, such images files would NOT look as desired when viewed on a display.  Correct?  Or NOT?

[rich2005]

Quote: However, such images files would NOT look as desired when viewed on a display. Correct? Or NOT?..

I would say not, you might get an approximation, I thought my last sentence But this is a RGB image, once it gets translated by the printer to CMYK then expect some change. covered that.

Worth looking at this post: https://discuss.pixls.us/t/using-online-...gimp/12854 and maybe joining in the discussion. One comment
Calibration is about making known, measurable colors display correctly. After I calibrated, my screen looked “worse,” less saturated and sort of dull. But the colors matched my printer exactly.

Great if you have a dedicated computer only used for photo editing. I have to use mine for other purposes as well. However I do know the limitations, I know what I print will be darker than what I see on the monitor. I use linux and the gutenprint gimp plugin. I can make a 'judgment' correction there.

However, on one of those previous screenshots I used a fuji colour profile. You would use it with paper as described here: https://www.digitalab.co.uk/metallic-prints No way I will ever get an exact reproduction on a computer monitor.

Think back to roll film days, The photographer started with a tiny contact strip, might make a test print with varying exposures before making a final print. It was an art then. Even in the digital age, still an art.

Quote:Insofar as my interest had to do with things I'd be adding to the image, text and borders, I'm thinking this means that I could use an alpha channel to create these things as transparent which would then cause them to be whatever the color of the paper on which they are printed.

That was covered in a previous post. For a simulation in Gimp over a base layer. A better way for text / border is using a layer mask. see: https://www.gimp.org/tutorials/Layer_Masks/

For sending to a printer. back to: there is no white ink, white = transparency

[ajax]

Yes, I am familiar with all you mention about display calibration.  While I have a pair of computers on a KVM switch that I use for photo editing the duller display doesn't bother me at all.  In fact, I think it is better for these aging eyeballs when spending many hours working with said display.

Similarly, I had huge problems with printing.  The biggest factor was learning about the need for different color profiles to match with different kinds of paper.  While I think soft proofing in GIMP and other editing software is useful it looks to me like you still need to allow some out of gamut (blown out) colors because removing them all can deteriorate the overall quality of the pictures.  Of course my novice status as a photo editor is likely also a factor.  As a result, the amount of correction I'm able to do with soft proofing requires some very subjective judgement.

This whole discussion seems to me to provide a pretty good explanation for why good pictures, that you'd like to preserve, need to be printed.  When the only thing you know about the electronic display devices that any audience might be using to view pictures is that they are very different from each other it looks hopeless, to me, to think you can rely on that method for sharing pictures where any semblance of quality is desired.  I think that is the main reason for wanting to spend time and effort undertaking the work associated with photo editing.  I'm often annoyed by how good the camera does on its' own and the difficulty I experience trying to improve on it.

Anyway, thanks for helping.  No doubt this discussion wondered into areas I had no idea of when my original question was posed.  I think I can conclude that what I original had in mind simply cannot be done.