I've got a comics drawing, only the black stroke, which is drawn by hand so the thickness is variating, and I need to draw a line with a thickness of 1 px in about the middle of this line. Is there a way to do it automatically?

enter image description here

The image I provided is an example of what I'd like to achieve on the whole picture, here I've drawn with the pen on a small section of the picture.

I tried with select/modify/contract and select/modify/border but there is no way to set an option which would leave at least 1 px in the middle. So when the two sides touch, they join and the middle of the stroke is no longer selected (using border) or simply disappears (using contract).

Can someone help?

1 Answer 1


What you ask is more suited for a vector editing program such as Illustrator or Inkscape. Even if the final objective is to have a raster image, converting your image to vector and performing a Centerline Trace will result in the single line you seek.

Once you have that, it can be reverted to raster with the single pixel line as desired.

The link above is for Illustrator. There is an extension for Inkscape to provide similar function, but I've yet to make it work properly.

After posting this answer, I realized I had neglected to include CorelDraw as another option for a vector editor with the same capability. I found a convenient YouTube video with instructions to create centerline trace using that software.

  • Thanks, though I haven't been able to achieve a nice result with Ilustrator's centerline trace and back to Photoshop yet. I didn't know CorelDraw so I'll check that.
    – Dante
    Commented Sep 3, 2018 at 11:31
  • There are complications with any of the applications in that it sometimes manages only single line tracks. A "Y" intersection may confuse the conversion.
    – fred_dot_u
    Commented Sep 3, 2018 at 14:15

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