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Change the sky using Gimp

If you have a scene with a sky that doesn't look interesting, have a go at swapping it for a better one. Michael Bates shows you how, using the free program Gimp.

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Even though a view can seem perfect when it is being photographed, there are often aspects of it that make you think, ‘If only that were different’. In a lot of cases this is can be altered by the photographer at the time, however in outdoor photography there will inevitably be factors outside of your control. One of these variables is, as we are all well aware, the weather. Even though this landscape view of Glossop is good enough, the sky itself remains boring, heavy and broody, what we want to do is introduce a new sky that will lighten the mood of the shot a little.

Gimp tutorial

Step 1 First things first, we need a sky. Pick an image that was taken on a day with similar weather to avoid overcomplicating matters or making the image appear too artificial.

Gimp tutorial

It’s always to have an image of a sky that is bigger than the image you are importing it to, that way you can choose which part of the sky you want to use and where you want it in terms of the image’s composition. We are going to take this sky, place it over the old one and cut out the trees and radio mast in the original so that they will show over the top of the new sky.

Gimp tutorial

Step 2 Open the image you wish to modify with GIMP and duplicate the background layer to begin with, renaming the new layer ‘foreground’. This is going to be the layer we will work with so as to avoid making any permanent changes to our source photograph and for the ease of reverting any mistakes that this affords us. With this layer active click the Quick Mask button (highlighted with a blue area in the screenshot) in the bottom right of the window or press shift q, and the image will be covered in a translucent red layer. The areas that are red are currently unselected while clear areas will be included and values in between the two will be the same as feathered selections.

Step 3 What we will do next is use the Paintbrush tool to remove the red from the trees and mast with a white, soft-edged brush before using a large, hard brush to remove the rest of the red in the lower part of the picture.

Gimp tutorial

Step 4 Now the trees and mast are within the cleared area, use the soft brush to go along the top of the hills so the selection along here is slightly feathered too, which will make the difference between this image and the new sky less obvious.

Step 5 Once this is done click the Quick Mask button again and the painted areas will turn into a selection, go into Select>To Path and your selection will be saved in the Paths pane for retrieval later on in the process.

Gimp tutorial

Step 6 Go into the image of your sky that you wish to use, select the sky with the rectangle tool and go to Edit>Copy or press ctrl c to copy it to the clipboard. Return to the scene you are editing and enter Edit>Paste or press ctrl v to paste it into the workspace. The sky will appear in your layers pane as ‘Floating Selection’, right click this and select ‘New Layer’ to turn it into a layer in its own right then position the sky roughly where it will be in the final image.

Gimp tutorial

Step 7 Place the ‘Foreground’ layer on top of the sky layer so it is temporarily obscured. Open the ‘Paths’ pane of the Layers panel and your selection from earlier on will be listed here as ‘selection’. Right-click and select ‘Path to Selection’ to bring the old selection back, and then click Select>Invert to turn the selection around so the sky is within the line of dashes.

Step 8 Press delete to remove the old sky and allow the new one to show through.

Step 9 There are now some parts of the old sky still showing around the edge of the trees and the mast, which makes it obvious that the sky has been changed. Zoom in and use a soft-edged Eraser to remove these edges, allowing the blurred edge to soften the edge of the trees so the image will look more believable.

Step 10 If you are having trouble getting the mast or something similar to blend convincingly with the new sky use the Lasso tool to draw around it and apply the Filter>Artistic>Soft Glow filter to so as to make the edges less defined and simulate the effect of the light bleeding into it slightly.

Gimp tutorial

Your image now has a more interesting yet convincing sky, as seen in the new version below.

Gimp tutorial

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I have tried to change the background sky with gimp 2.6 and I can get the new sky rectangle onto my image but cant get the foreground back in front also what about anchoring it.

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