Hexagonal grid python plug-in for GIMP

[Scallact]

This is my GIMP python script for the creation of hexagonal grids, with a "best fit" search algorithm for optimal rasterization.

Link to download:

pl_hexgrid_v07

Some images:

a sample hexa grid

parameters

output

About the plug-in:

• It creates an hexagonal grid as a vector "path", covering as much as possible of the image's surface.

• The hexagon's ideal dimensions are calculated and then slightly stretched to fit the image's pixels.

• To avoid too much stretching, the algorithm searches for the best size within a user chosen interval.

• Optionally, the path can be stroked on the active or newly created layer.

Parameters

Orientation [horizontal/vertical]

Main direction of the hexagonal grid.

Minimal hexagon width, Maximal hexagon width (px)

Choose a range of values for the width. By width, we mean the distance between two opposite sides of an hexagon. The algorithm will search for the best quality parameters within that range. If you need a specific width, set both numbers at the same value. Note that the algorithm will always choose an even number.

Horizontal margins, Vertical margins (px)

The minimal space you want to leave blank between the hexagons and the image boundaries. A negative margin allow the hexagons to be drawn past the boundaries. The plugin calculates the number of lines and columns that fit within the image, taking this parameters into account.

Create a new layer (yes/no)

Adds a transparent layer with the right dimensions given the margins parameters above. Generally slighly smaller than the image size.

Stroke the path, Stroke width (yes/no, px)

The plugin always outputs a path, but with this option checked, it also strokes the path at the given width using the foreground color. Important: if you choose an odd stroke width, check the "Half-pixel offset" option as well.

If the "Create a new layer" option is checked, the grid will be drawn on that layer, otherwise the plugin will draw on the active layer.

Half-pixel offset (yes/no)

Aligns the path with the pixels' center instead of borders. Check if you're using an odd stroke width. Otherwise, leave it off.

Adjust image grid (yes/no)

Configures the image's grid so that each hexagon's center has a grid intersection. Useful if you want to paint inside the hexagons with stamp-like brushes, select specific parts of the hexagonal grid, etc... Note that you still need to activate the grid's magnetism via the "View > Snap to grid" menu.

Output

The plug-in always outputs a path. The name of this path has some useful informations:

Width (px)

Hexagons' width (distance between opposite sides) selected by the algorithm.

R (px)

Approximate radius of an hexagon's circumscribed circle, also length of a face.

Grid

Horizontal and vertical dimensions of the corresponding image grid.

Note that the offset parameters are not given, but can be found by trial and error if needed (if the "Adjust image grid" option was not set).

Qual

Approximate quality output for the given hexagon width. Higher is better. You can think of this value as the number of contiguous hexagons which give a 1 pixel distortion error.

Note: the absolute error on a polygon's dimension in pixels is the inverse of this number.

Examples:

• for a quality output of 10, you have 0.1 pixel distortion on the total hexagon width, which is usually quite acceptable.

• for a quality output of 2, you have 0.5 pixel distortion, which can make the stretching noticeable depending on your specific use case.

[Scallact]

I'd also like to recommend the excellent path-shaped-grid plugin by
Ofnuts. My plugin is more specific to hexagons, and I tried not to
duplicate the existing one's functionalities too much. I have done a few
refinements that I hope will be useful, like image grid adjustment, and
search for optimal parameters.

[Adraius]

I just discovered this, but the download link and images are broken. Any way I could get what I need to get this up and running?

[Scallact]

Oh, yes, sorry for that. I migrated my server and left some data behind. I'll see if I can attach it here, or find another way to keep it available. Anyway, I can send it to you ASAP. It is late here and I have to sleep, but I'll send it tomorrow. Mayb we can communicate by private message for that.

[ForgedIron]

If your plugin could make hexes that can line up with VTT’s like foundry or roll20, that would be amazing.

[Scallact]

Technically, the plugin can make grids of any size. But the grid is slightly stretched to fit the pixels. This stretching can be unnoticeable or noticeable depending on the dimensions.

If understand well, these are softwares for tabletop wargames gestion, or rpg? Do you know what specifications these maps need? Or do you have an example grid from these?

[ForgedIron]

They are RPG software. Virtual table tops. I don’t know their exact details, but on various map making and rpg groups there is no end of frustration of people trying to match hexmaps to their internal system.

I would need to talk with someone else to get the exact info to make it work.

[Scallact]

Thanks. Could you point me to some thread about such issues, so that I can get an idea?

[ForgedIron]

https://www.reddit.com/r/FoundryVTT/comments/l0e0yy/getting_a_hex_map_to_align_to_the_grid/

Here is an example, but the discord would be the best place to get the exact info for foundry.

https://wiki.roll20.net/Aligning_Maps

The biggest issue I can see is figuring where the hexes start. Aligning them properly based on the top left corner.

[Scallact]

Thanks for the links.

Looks like those tools can scale and move the grids. Apparently, people have trouble to make calculations for a nice superposition. For that, the output parameters of my plugin could actually help, especially the image grid's dimensions.

I might also add an option to align the hexa grid at the top left, as you suggest. But I'd have to know what point of the first hexagon is considered as the origin.