# GIMP plugins¶

If you use The GIMP there are two plugins available for you to use Kotyle:

• a plugin to measure capacity and save a vector path as GeoJSON data
• a plugin to rotate an image based on a straight line

It is very easy to install and use these plugins. The README with installation instructions is here together with the plugins.

The GIMP is a is a freely distributed piece of software for image retouching and manipulation, available for all operating systems.

## Before you start: check image resolution¶

It is very important that you check the image resolution is the correct one, e.g. if you scanned a drawing at 300 dpi the image file must be set at the same resolution, otherwise all measurements will be wrong.

You can set the image resolution from the Image ‣ Print size... menu item.

## Vector paths in GIMP¶

Both plugins work with Paths in GIMP. Paths are separate from the raster layers and can be drawn on top of the existing layers.

There is a specific panel for Paths where they can be removed and renamed. Renaming is important here because we will need to be able to pick one or more paths and use them with Kotyle.

You can find the most recent documentation about paths in the GIMP Manual.

## Drawing a vector path for a vessel profile¶

The Path tool allows you to create vector paths. You should either start from the vessel bottom (foot, base) or the top (rim) taking care to draw along the inner profile (assuming you want to calculate the volume of the vessel content).

Make sure you draw only one path for the profile. When you’re done, go the Paths panel in the main toolbox (close to the Layers panel) and rename your path to something useful, like Bowl Type 23.

## Measuring vessel capacity¶

Go to the Plugins ‣ Kotyle menu (it should be close to the bottom of the menu) and click the Measure vessel capacity item.

A dialog will open, where you need to choose a few parameters:

• the path (directory) where you want to save the file
• the name of the file (default is profile.json but you want to choose a more sensible name if you have more than one profile) where to save the GeoJSON data of the vessel profile
• the vector path you want to export – you will see that the drop-down list shows you the names of paths – you can choose only one path
• title, description and author of the drawing, optional but useful

The result will be shown in the Console panel. You may need to enable it.

## What to do with the GeoJSON?¶

In short, you are going to have one .json file for each profile you want to measure. These files are nothing special, you can open them with any text editor and look at their contents.

More details about the GeoJSON format are found in Describing the profile of a vessel in a digital format.

The Measure vessel capacity plugin will save your vessel profile in a file (e.g. named profile.json).

Kotyle has a separate tool to calculate vessel volume from that file, called Μετρω, the Kotyle measurement tool. In the future the plugin will be capable of showing the vessel volume directly in the GIMP window.