I am trying to smooth out images of colored wave forms while trying to keep sharp edges.

Example of a source image:

enter image description here

I've had some limited success using surface blur, while the transitions between each color is smoother I am loosing sharpness on edges:

enter image description here

Is there a technique, filter of effect I could employ to get such result ?


here's the result thanks to @boblet

enter image description here


I've found a pseudo-alternative that somewhat achieves the same goal though it's not as pretty.

enter image description here

The thing is to draw gradient lines with the middle color (0.5) being a little darker.

Actually this is the poor man's alternative until I can get hold of the surface blur algorithm which doesn't seem as easy to implement as it sounds.

  • What software are you working with?
    – benteh
    Mar 30, 2014 at 16:40
  • I did that with Paint.net but I can use Photoshop and Gimp as well.
    – aybe
    Mar 30, 2014 at 16:42
  • So what you want are a blur between the colours "inside" the shape, but keep the sharp edge with the white background?
    – benteh
    Mar 30, 2014 at 16:45
  • Yes exactly that.
    – aybe
    Mar 30, 2014 at 16:48
  • 1
    I don't know where you get the source images from but if you have a way to produce a waveform with the color distribution you want but without any white area left (maxed out everywhere), you could blur that and put the white from the image you have now as a layer on top. That way you wouldn't dilute any colors with white as you do now.
    – Christian
    Mar 30, 2014 at 22:27

1 Answer 1


Paint.net and Gimp

Below is a detailed example of how to do this in Photoshop. However, both Gimp and paint.net have the same capabilities, though the tools have slightly different names.

The Gimp equivalent to Photoshops magic wand tool is Fuzzy select. You should be able to achieve the same result.


Select the white background with the magic wand tool You do this by first clicking on the top part of the white, hold shift and then select the bottom part. enter image description here

Right click, and choose select inverse from the menu.

enter image description here

Choose the blur tool,

enter image description here

and blur your colours into each other to your hearts content. enter image description here

  • 1
    Happy to help :)
    – benteh
    Mar 30, 2014 at 17:01
  • @Takkat maybe you could make that an answer, for future reference?
    – benteh
    Mar 30, 2014 at 20:09
  • 1
    Paint.Net also works the same way Mar 30, 2014 at 20:45
  • Heheh, paint too. Nice. Good to know; I will see if I can incorporate this in some way.
    – benteh
    Mar 30, 2014 at 20:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.