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Feathered edges

  • Category: Gimp
  • Published: Friday, 16 June 2017 13:05
  • Written by Super User
  • Hits: 212

Working with images often involves merging two or more layers. Unfortunately, the sharp edges of layers can sometimes be visible to the eye. This article looks at various ways to hide these joins.

The eye is very good at detecting regular shapes such as squares and circles. If it is possible to make an irregular shape with gentle curves it is far less visible. (The same technique works well with wallpaper when decorating!).


A more powerful approach is to work with selections. In addition to selecting standard shapes it is possible to use the intelligent scissors, or the path tool, to create the shape. I will cover their use in more detail in another article. It is also possible to select by colour.


In  this example I used the top menu (layers, duplicate) create a second identical layer. Using the top menu (windows, dockable dialogues, layers) you can see the two layers. Clicking the eye symbol will make a layer appear/disappear. The active layer is shown as coloured.

Next use the intelligent scissors to track round the red truck. I used quite a lot of datum points to the give the tool a fair chance of selecting this complex shape. Having completing the shape a mouse click anywhere within the shape will convert it to a selection. Next use the select menu to invert the selection. Invert again and you will have a layer showing only the truck. You move this about to demonstrate this but move it back to cover the lower truck precisely.


There is a pitfall here. Before deleting the inverted selection go back to the Layer Dialogue and make the inverted selection the active layer. Right click and add alpha channel. This will allow you to make the deleted part transparent. Without the alpha channel it will appear white.


We would now like to blur the the edges of the selection slightly to make the merge better with the lower tool. One way to achieve this is to use the top menu selection, feather. This will feather a few pixels around the edge of the selection and mask the join slightly.


Make the lower layer active. Select all and from the top menu Colours, BW film simulation (there are several other ways to simulate monochrome film). The old red truck should now be in colour while the background is in monochrome. As a final touch try selecting the lowe layer the use Filters, Decor, Fuzzy border.


Finally use Image, Merge visible layers to give you a single layered image for export.


 (Original image of truck copyright Vandervegt6613,, modified image copyright Neil Turner creative commons 3.0 attribution unported.)

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