Preparing Scanned Handdrawing for Vectorization

Today I started to vectorize some old black and white handdrawn designs I created a long time ago. And I ended up with the problem, that some of the scans had a lot of speckles. One of this drawings was the following “skeleton sperm” or whatever you wanna call it:

Doesn’t look that bad, but when you some in you can see a lot of annoying pixels around the lines:

When using Inkscapes “Path >> Trace Bitmap …” feature to vectorize the above image, I ended up with yome really ugly paths:

Years ago I used to remove this either in the bitmap or the path with a lot of effort by hand. Today I found a really nice technique to avoid all that tiresome work.

Step 1: Add Mask to Image

  1. Open your scanned drawing in Photoshop.
  2. Use “Image >> Adjustment >> Brightness / Contrast…” and increase the Brightness and contrast a bit to remove all the potential noise you have in the white part of the image.
  3. Open “Window >> Channels” and Ctrl-Click the RGB Layer to make a selection of the image.
  4. Add a mask to you drawing using “Layer >> Layer Mask >> Hide Selection”

Step 2: Refine Mask

Now you can use the “Select >> Refine Mask Feature to refine the Selction and get a smoother look. For me the following settings have worked well. This depends on the size of your image and other factor, have fun playing around with these sliders.

Refine Mask Settings

Step 3: Create a Solid Color Layer

  1. Use Ctrl+Click on the refined layer mask to create a selection from the layer mask.
  2. Use “Layer >> New Fill Layer >> Solid Color” and choose black as the color.
Create a solid color layer with a refined mask.

Step 4: Vectorization

Save the image and open it in Inkscape. When you now trace the bitmap image using “Path >> Trace Bitmap …” the result will get much smoother without all the speckles.

Above the Bitmap and below the results after vectorization.



Leave a Reply

Your email address will not be published.