Pixey

The easiest, and free way, is to use this service:  https://www.remove.bg/

It may have been this one?  If so, it's Ed Harvey.
 

Hello @flaviusCrispus and welcome
 
There is another Clouds Plugin which may be what you are looking for.
 

Okay, you need to practice using layers ....... and to get used to what the "select" an image can do.
 
1.  On one layer, have your scanned image.
2.  Draw a rounded rectangle on a new layer: rectangle shape found in the shapes area, under basic shapes.
3.  With the magic wand, select the inside of the rectangle.  Check flood mode (in the upper bar on the canvas) is set to 'contiguous'.
4.  Move to the image layer and use Ctrl + I on the keyboard, which will invert the selection.
5.  Then hit Crop to selection - or just  hit delete.
6.  Uncheck the rectangle layer and flatten.
7.  Use AA's Assistant to clean up.
 
But, remember that saving as .png will retain transparency.
 

You could also:
 
1.  Draw your curve and fill the first color.
2.  Gaussian Blur.
3.  Fill the second half.
 

Hello @Pixie1001 and welcome to the forum
 
There is another Grid Lines  in this pack that goes up to a thousand.
 
If you want it bigger than that, you could duplicate it and then increase your canvas size and rearrange it to meet up.

Hello @Garrymo 
 
Until there is (who knows?) a square brush, you can always use the "bracket" keys to decrease, or increase, the size of the brush.
 
Please see the short cuts here:  https://www.getpaint.net/doc/latest/KeyboardMouseCommands.html

You could always find a font:  https://www.1001fonts.com/comic+outlined-fonts.html
 
Then magic wand the inside of the font and delete the center.
Follow by Gaussian Blur and AA's Assistant.
Then magic wand the center again and fill with desired color.
 
* Edit:  Actually you don't need to get rid of the color, as the outline text is clear:
 

@pdn_mark I've been tinkering with this, using Levels helps a tad, then duplicate the layer and mode to Difference.
 
I can see that the Bar Bill was huge -  must have been a good party.  Reminds me of the time my husband and I went to the bar at the Danieli in Venice 😁
 
 
 
 

Hello @Thisisme here is a video that should help you to accomplish this by using the Gradient tool:
 
 

And, when you are back up and running @Azure this is how to make your text transparent:
 
1.  Use the magic wand to select the text.  Play with the Tolerance in the top tool bar, until it 'selects' only the dark area.
2.  Hit delete.
3.  Clean up the 'hole' where the text was by using Feather or AA's Assistant.

You can download it again from here 

Hello @imgspace1484 here is a simple tutorial which may help you.  I guess for your purpose, only use the bevel a bit less on your font:
 
https://www.youtube.com/watch?v=WrKTUDICwik
 
Also, here is a quick idea of how to use the gradient only:
 

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Hello @jacknw and welcome to the forum  
 
You will need to have your text on its own layer, in order to stretch it out.
 

If you can't separate your text, then you could try using the Rotate & Zoom.  But it probably won't help much.
 

Hello @hans peter  
 
Please try to download from here:
 
 
 
And another version can be found here.
 
 
Classic or Store bought - "And is this important anymore in this context?"
 
Yes, because the Effects Folder (for the Plugins) will have to be made manually for the Store Bought version.
You will know if you have the store bought, as it will have updated paint.net automatically and you would have paid $9.99 for it.
 
When in paint.net you can find the Circle Plugins in the Effects > Text Formations:
 

 
 
 

Hello @msh  
 
You could make this by using the Shape Maker Tool and here are some tutorials on how to use it.
 
You also make a simple one by using the line curve tool as a template, and then using gradients to fill the parts:
 

 

@Astraziel try using AA's Assistant afterwards.

@BMP I took a quick look at the Pumpkin video and these are the tool used, which can be found in the Plugin Index.
 
1.  Gradient Tool
2.  Tube Oblique
3.  Tile Image
4.  Invert Selection
5.  Clouds
6.  Perspective
7.  AA's Assistant
8.  Tube Oblique
9.  Shape 3D
10. Liquify
11. Brightness / Contrast (built in)
12. Color Tint
13. Gaussian Blur
14. Hue / Saturation (built in)
15. Vignette (built in)  

You can use @BoltBait's Bevel Selection Plugin.
 
Select the shape, then use the adjustment in both the shadow and colors area.
 
 

Perhaps you are thinking of this one, I use it and it's still working for me in the latest versions of paint.net   
  

Hello @Darthaizen it looks like you may have to use this tool, and then try to reinstall Paint.net again.
 
https://support.microsoft.com/en-us/help/17588/fix-problems-that-block-programs-from-being-installed-or-removed

It's working for me - Ctrl + Shift + X = to crop to selection.
 
There was a Windows update yesterday, perhaps it's a hiccup 🤔
 
P.S.  Also, it's a popular hotkey.  Did you download any new software?

This tool can be rather frustrating.
 
We were discussing this subject here a few days ago.
 
You may want to read through the subject on this tool:
 
https://www.getpaint.net/doc/latest/RecolorTool.html

A video I made some time ago:
 
 

Sorry, you can't.  Please read this post for the reason why:
 
 
@null54 beat me to it by a nano second 😹