This GIMP (GNU) tutorial demonstrates how to replace a dull sky with a Gradient using the Blend Tool. To work along, you are welcome to download the Start Image
I am working with Here. Unzip the file and open the image onto GIMP’s workspace.
You can quickly Undo a step at any time by pressing Ctrl then Z. Alternatively, click a previous Undo History snapshot - Windows then Dockable Dialogues then click Undo History. In addition, to Zoom in (or Zoom out) of your image; from the top menu, choose View then select a Zoom Tool from the subsequent drop-down list.
Understand Blend Modes
Launch GIMP & Organise Its Workspace & Palettes
Open your choice of Start Image onto GIMP’s workspace - File then Open - Ctrl then O.
Ensure the Layers and the Undo History Palettes are visible, and then drag them into position over your workspace - (Windows then Dockable Dialogues - then click Layers and Undo History).
Now, from the Layers Palette, create a New Transparent Layer by clicking the following Create a new layer tab.
Then from the subsequent New Layer dialogue box, enter a suitable name for the New Layer, and then click OK.
Click open each colour swatch, one at a time. And set the Foreground Colour Swatch to Light Blue and set the Background Colour Swatch to Solid White. (Alternatively, set sky colours of your choice).
Then from the left-side Toolbox, activate the Blend Tool.
And set the following Foreground to Background - FG to BG (RGB) Gradient settings into the Options Bar.
Now, still working on the Sky Layer: press down the Ctrl Key and simultaneously left-click and stretch vertical “Gradient Line” in the direction illustrated below.
As soon as you release the mouse button, a Foreground to Background Gradient will be applied over your image.
It’s important to experiment with the “Gradient” Line’s Direction and find a look you are happy with. By this I mean the Gradient Line does not have to be stretched over the full depth of the image; - perhaps stop half up, or a quarter way up or down, and create a gradient you prefer.
Gradient Shape Note
For personal results, experiment with GIMPs Gradient Shapes.
From the Layers Palette; change the Sky Layer’s Blend Mode from Normal to Darken Only.
Images will always react uniquely. The Darken Only Blend Mode is perfect for my Cannon Image. However, when utilising your own images, it’s important to play with different Blend Modes. In addition, if the blend is too dark, you can lighten it by reducing the Sky Image’s Opacity.
Eraser Tool Tip
If necessary, you can remove unwanted Gradient Pixels with the Eraser Tool.
When you happy with your work: from the top menu, choose Image and then choose Flatten Image.
To create extra impact, apply a Sharpening Filter of your choice - Filters then Enhance.
Congratulations, your work is complete, and it is ready to save - top menu, then File then Save As.
Now you are familiar with this technique, you can have lots of fun replacing dull skies with a Gradient of your choice.
Wendi E. M. Scarth. Top of Page.