How to remove background fully?

[gumbo23]

When doing erase white paper, I still get a lot of the background.

What operations do I need to perform in order to completely erase the background?

[NotMyFault]

This image seems to be a simple circle. So a ellipse shape used as vector mask will do the trick.

Or do you intend to erase the inner light lines?

an ellipse of 3450px size seems just right. I added a 2x plug via layer fx to smooth the edge.

 

[gumbo23]

29 minutes ago, NotMyFault said:

This image seems to be a simple circle. So a ellipse shape used as vector mask will do the trick.

Or do you intend to erase the inner light lines?

an ellipse of 3450px size seems just right. I added a 2x plug via layer fx to smooth the edge.

 

This is great - would you mind sharing the file with me? I couldn't figure out how to mask it. I'm way out of practice!

[NotMyFault]

Here you go.

i added 2 groups for the inner circles, using blend mode erase. But those circles are more irregular, it does not work well.

circles and mask.afphoto

[gumbo23]

7 minutes ago, NotMyFault said:

Here you go.

i added 2 groups for the inner circles, using blend mode erase. But those circles are more irregular, it does not work well.

circles and mask.afphoto 21.5 MB · 0 downloads

Amazing! Much appreciated. And you're right: Hamburg is pretty great. St. Pauli rocks

[Old Bruce]

4 hours ago, gumbo23 said:

When doing erase white paper, I still get a lot of the background.

What operations do I need to perform in order to completely erase the background?

To be honest I don't see any white paper, I see yellow to blue.

[PaulEC]

30 minutes ago, Old Bruce said:

To be honest I don't see any white paper, I see yellow to blue.

This sort of thing seems to come up quite often with the "Erase White Paper" filter, and I think part of the problem is down to the name. People seem to think that it will somehow know that an off-white background, with a texture, is the "white paper" and that it will remove it, leaving all other colours intact. It would be more accurate to call it a "Remove White" filter, which is what it actually does. It removes all the white from the image, meaning that any pure white becomes fully transparent and all other colours which have any amount of white in them become partially transparent. It is useful if you have a line drawing in a solid colour (typically black) on a solid white background, but, unless you want some weird effects, it is not the right tool to use to replace the background in images such as in the OP.

[NotMyFault]

It is possible to use erase white paper in those cases with a trick.

1. Use any suitable adjustment like white balance, curves, etc to map the unwanted color to white.
2. erase white paper 
3. apply the inverse adjustment (needs manual calculation, there is no auto function)

[NotMyFault]

4 minutes ago, PaulEC said:

This sort of thing seems to come up quite often with the "Erase White Paper" filter, and I think part of the problem is down to the name. People seem to think that it will somehow know that an off-white background, with a texture, is the "white paper" and that it will remove it, leaving all other colours intact. It would be more accurate to call it a "Remove White" filter, which is what it actually does. It removes all the white from the image, meaning that any pure white becomes fully transparent and all other colours which have any amount of white in them become partially transparent. It is useful if you have a line drawing in a solid colour (typically black) on a solid white background, but, unless you want some weird effects, it is not the right tool to use to replace the background in images such as in the OP.

This is totally correct. Nevertheless, you can use this as starting point and use additional adjustments (curves, levels, fill layer with BM divide) on alpha channel to only impact the „to be removed“ background and add a white fill (or any other color depending on artistic intention) for other areas.

[thomaso]

16 hours ago, NotMyFault said:

apply the inverse adjustment (needs manual calculation, there is no auto function)

What's the "inverse" setting for a certain Levels Adjustment for instance (which was used before to achieve White for the "paper" colour successfully)?
Can you show screenshot examples of the settings in step 1. and 3.?

[NotMyFault]

it won't work for this image, as the background has a strong gradient in hue, lightness, and saturation. I assume this is part of the artwork and not "just background" and a mix of lightning in the room.

[thomaso]

4 minutes ago, NotMyFault said:

it won't work for this image, as the background has a strong gradient

Apart from this specific image: What do you mean by "inverse" for that adjustment which turned light tones into white in the first step?

[NotMyFault]

Say you have a certain RGB color. For simplicity I choose the red channel. Repeat process for other color channels.

if it is 75% red, add a levels adjustment on red channel and set white level to 75%. 
to reverse the effect, use another levels adjustment and set white output to 75%.

 

this assumes that the background color is the lightest color of the image. If not lighter colors shout get blown out.

 

[nickbatz]

Let's say this weren't a circle but rather a very complicated shape that you wanted to isolate from its background.

Affinity Photo (that's the one I use, not sure about the others) has several selection tools, as well as Quick Mask and Refine features to fine-tune the selection. It's worth watching the tutorial videos, but my first attempt in this example would be Select Sampled Color (unless the oval/circle one worked).

Anyway, you make the selection, then Invert Selection (Selection menu), and hit Delete. That removes the off-white paper and leaves the object.

[PaulEC]

16 minutes ago, nickbatz said:

Anyway, you make the selection, then Invert Selection (Selection menu), and hit Delete. That removes the off-white paper and leaves the object.

I would never use Delete, as it's destructive; I always use a Mask, so that it's easy to edit/clean up the image! (Which, most of the time, it is!)

[nickbatz]

1 hour ago, PaulEC said:

I would never use Delete, as it's destructive; I always use a Mask, so that it's easy to edit/clean up the image! (Which, most of the time, it is!)

I use masks all the time too, and pretty much always leave a trail back one way or another. You're right about that, of course, although in this case I think there's the original file to go back to if you need the paper background again?

In any case, there are many ways to go about things. Thinking about it, in this example I'd probably copy the extracted circle and paste it to a new layer, then turn off the one below. But I use the program very differently from the way most people do, and the way I'd do this would depend on what I'm doing next.

I was just trying to make this simpler, without having to bother with channels and changing colors, etc.