Using pen tool to select a thin line?

[zBernie]

In the image below I'm trying to create a selection of the very top of curved dome.  But when I click the pen tool "Selection" button, the selection becomes enlarged as shown in the second screenshot.   What I'm trying for here is a 1 or 2 pixel wide selection of the top of the dome.  Is it possible to close the curve in such a manner?

[Alfred]

Try tracing along the curve with the Smart Selection Brush Tool, using a brush tip width of one pixel.

[zBernie]

6 hours ago, Alfred said:

Try tracing along the curve with the Smart Selection Brush Tool, using a brush tip width of one pixel.

 

I tried but I can't keep the brush on the line.  No way to do this with the pen tool?

[NotMyFault]

You can do it in different ways using pen tool. My preferred way of masking.

Important: Do not close the curve!

1. if you want to use the stroke color as mask, set a stroke color and 2px stroke width. Use it as vector mask, or rasterize to mask, or create selection from layer.
2. if you prefer a closed curve, use „expand stroke“ after setting stroke. This will result in a closed curve you want.

I used 8px with in the example below to make the thin line visible.

[GarryP]

zBernie: You don’t say which Affinity application(s) you have access to but if you have Photo you can select via a curve by using the technique shown in my attached video (the selection in the video isn’t exact, it’s just for demonstration purposes).
Create the curve, give it an appropriate width, then use Selection from Layer.

[zBernie]

9 hours ago, GarryP said:

zBernie: You don’t say which Affinity application(s) you have access to but if you have Photo you can select via a curve by using the technique shown in my attached video (the selection in the video isn’t exact, it’s just for demonstration purposes).
Create the curve, give it an appropriate width, then use Selection from Layer.

 

Ah, selection from layer!  That's what I was after.  I was pulling my hair out trying to find a solution with the pen tool options.  You would think there would be an option to draw a line and NOT close it.

[R C-R]

33 minutes ago, zBernie said:

You would think there would be an option to draw a line and NOT close it.

??? Lines (curves) are not closed automatically, so I am not sure what you mean by that.

[zBernie]

49 minutes ago, R C-R said:

??? Lines (curves) are not closed automatically, so I am not sure what you mean by that.

I've found that the curve is always closed regardless of what I try to do.  I don't have a lot of experience with the pen tool, but I've tried various options and find the curve always closes.  Unless as GarryP posted you make a selection from the pen layer.

[R C-R]

12 minutes ago, zBernie said:

I've found that the curve is always closed regardless of what I try to do.

The curve shown in your first post is not closed; however, when you use the "Selection" button on the Pen's Tool's context toolbar the selection made from that curve automatically includes everything between the start & end nodes, as if there was a straight line between those nodes.

So to avoid that, do like in the video @GarryP posted & instead use the Select > Selection From Layer menu item, after setting the stroke width to a suitable value.

[R C-R]

14 hours ago, NotMyFault said:

2. if you prefer a closed curve, use „expand stroke“ after setting stroke. This will result in a closed curve you want.

FWIW, from the comment by the OP about using the Pen tool "Selection" button, I think the app being used is AP, so Expand Stroke is not available, since it is a feature of AD but not AP.

[zBernie]

3 hours ago, R C-R said:

The curve shown in your first post is not closed; however, when you use the "Selection" button on the Pen's Tool's context toolbar the selection made from that curve automatically includes everything between the start & end nodes, as if there was a straight line between those nodes.

So to avoid that, do like in the video @GarryP posted & instead use the Select > Selection From Layer menu item, after setting the stroke width to a suitable value.

Look at the 2nd picture in my original post, it is closed.  Therein lies the problem.  In my opinion the pen tool in AP should have an option similar to what creating a line, then creating a layer from that selection does.  Seems it should be intuitive but it's not.

[R C-R]

21 minutes ago, zBernie said:

Look at the 2nd picture in my original post, it is closed. 

What is shown in your second picture is a "marching ants" selection. It is not a curve. Like I said, that happens in AP if you have the Pen Tool selected & use the "Selection" button on the Pen's Tool's context toolbar.

So don't do that! Instead do as shown in Garry's video at about 0:15 & use Selection From Layer on the Select  menu. And since it is a menu item, it has a keyboard shortcut (which can be changed in the shortcuts preferences if you want) to make it quick & easy to use without having to open a menu.