Earlier today, I changed my avatar on Twitter. It's for fun that make avatar look like blank image. However, you still can see something from the avatar.



So, here comes this post. I use GIMP to make another one from a cat image. The original is



(Kind of cool face, isn't?)


The rough steps

  1. Firstly, open it and duplicate the layer. And don't forget to add alpha channel. Name the duplicated layer as Edge.


  2. Apply Filters Edge-Detect Sobel... on Edge layer. The result looks like






  3. Remove some unwanted edges, only leave the main part. In this case, the cat's head.

  4. Add Black (full transparency) layer mask to Source layer.

  5. Copy Edge layer onto Source's layer mask.

  6. Reduce Opacity to make the image be barely seen.

  7. Enhance if the ghost image is not evenly seen:

    a) Duplicate the Edge as Enhance.

    b) Remove the parts that are too strong from Enhance layer.

    c) Adjust Opacity of Enhance layer to make ghost image looks balanced.


The final image




Yes, it's right above. (I set the opacity way too low. :p) The final GIMP file is here.