This is an update to the old method I showed you.
This method is faster, less complicated, and is better at dealing with edges. You still get good results, and you can see what is happening in real time.
10 July 07 – Edited step number 3 so that the whole thing works now!
I used this image in my example (about 182kb): creation_of_adam.png
1. Duplicate the layer. Call this (top) layer ‘Shape’. Select this layer.
2. Open the Despeckle Dialog ( Filters -> Enhance -> Despeckle). Uncheck the ‘Adaptive’ and ‘Recursive’ check boxes. Set the Black Point to -1 and the White point to 256. Adjust the radius until the blemish that you want to heal disappears. In Gimp 2.2 make sure that radius is odd (there is a bug in 2.2 that is fixed in 2.3)
3. Change the layer mode to ‘Grain Extract’. Select ‘Copy Visible’ from the Edit menu. Paste this and convert it into a new layer. Name this layer ‘Texture’. Change the Mode to ‘Grain merge’. Change the ‘Shape’ Layer’s mode to ‘Normal’.
4. Show only the Texture layer. Select a hard brush and clone over the blemish. Make both the ‘Texture’ and ‘Shape’ layers visible to see the result. You can clone the texture layer while both layers are visible to see the results as you do it if you like.
5. You’re done.