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Alien Map Filter 


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Apply A Colourful Alien Map Filter To A Photograph
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Apply GIMP's Alien Map Filter

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This GIMP (GNU) tutorial demonstrates how to bring a photograph to life by applying GIMP’s colourful Alien Map Filter. To work along, you are welcome to download the Start Image I am working with HereUnzip 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.

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 top menu, choose Colours then choose Map and then choose Alien Map. And from the subsequent Alien Map dialogue box, experiment with the settings, and then click OK.

Alien Map Filter Notes
This filter renders very modified colours by applying trigonometric functions. Alien Map can work on images having RGB and HSV colour models.

This preview displays results of filter application interactively.

Buttons RGB Colour Channel and HSV Colour Channel let you select the colour space you want to use.
Tick Boxes (Modify, Channel), let you select the RGB/HSV Channel you want to work with.

For each channel, you can set Frequency (0-5) and Phase shift (0-360) of
sine-cosine functions, using either sliders or input boxes and their arrowheads.

Frequency around 0.3 to 0.7 provides a curve that is similar to the linear function (original image), only darker or with more contrast. As you raise the frequency level you'll get an increasing variation in pixel transformation, meaning that the image will get more and alien.

Phase alters the value transformation. 0 and 360 degrees are the same as a sine function and 90 is the same as a cosine function. 180 inverts sine and 270 inverts cosine.

Sharpen Tip
Your image will benefit from a Sharpening Filter: Filters then Enhance

Sharpen Images Tutorial.

Congratulations, your Alien Map Conversion is complete,
and it is ready to save - top menu, then File then Save As. GIMP 2.8 - File then Export.

Apply GIMP's Alien Map Filter

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