8.21. Alien Map
| 8. The “Colors” Menu |

### 8.21. Alien Map

#### 8.21.1. Overview

Figure 15.154. Alien Map filter example

Original image

Filter applied

This filter renders very modified colors by applying trigonometric functions. Alien Map can work on images having RGB and HSV color models.

#### 8.21.2. Activate the filter

You can find this filter in the image window menu under Colors → Map → Alien Map.

#### 8.21.3. Options

Figure 15.155. Options for the “Alien Map” filter

Preview

  This preview displays results of filter application interactively.

Mode

  Radio buttons RGB Color Channel and HSV Color Channel let you select the color space you want to use.

  Check boxes Modify ... Channel let you select RGB/HSV Channel you want to work with.

Sliders

  For each channel, you can set Frequency (0-5) and Phaseshift (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 more “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.

8.20. Set Colormap |  | 8.22. Color Exchange