Replacing The Sky - Gimp
There are times when it may be desirable to replace the sky with another one which is visually more appealing. Perhaps the sky is blown and appears white or it is just plain dreary!
You could use the technique that I described in the article about Removing Image Backgrounds which uses the quick mask. You would of course need to go one step further than described in that article. You would need to add another layer (ctrl + L - will open the layers dialog box) below the main picture and paste the new sky into this layer. It will be visible on all the transparent parts of the image.
With the example images below I used a different but equally effective technique to achieve the required result.
Open up your image for editing in the Gimp and add an alpha channel to your image
Using the magic wand select a continuous region from the sky area of the image.
Using Ctrl + K clear the selected area - this will result in the selected area being changed to transparent.
Using Ctrl + L open the layers dialog box and add a new layer for the sky. Then paste and anchor your favorite sky into this layer. Then drag this new sky layer below the background to allow for it to show on only the transparent area.
Select Ctrl +Shift + A to remove all selections.
Flatten the image from Image > Flatten Image and save as the required file!