Guillot

A naive and greedy but occasionally clever algorithm for placing a collection of differently-sized images on the smallest possible number of same-sized pages, ensuring that the images can be separated by making only guillotine cuts, that is, all the way across the paper.

I found a lot of academic papers on the topic, but not very much working code. The closest I got was opcut, but it ran for over 400 hours and never terminated on my sample input.

So, I wrote my own, and it runs in much less time, giving great results. It worked great for my use case (576 images with 430 distinct sizes) so I stopped, but cleaned it up for you. If I do any more, it will be to resolve the TODO items in the code, which are points of tuning and finessing. Pull requests welcome!

License

Copyright 2020 by Tom Rathborne [email protected]. Licensed under GNU GENERAL PUBLIC LICENSE Version 3, 29 June 2007. See file LICENSE for a copy of the license.

Requirements

• Ruby ... not sure of the minimum version, since this is my first Ruby program! I used ruby 2.7.0p0 (2019-12-25 revision 647ee6f091) [x86_64-linux-gnu] as found in Ubuntu 20.04.
• Ruby's yaml and optparse modules which seem to be part of libruby.
• GraphicsMagick, in particular the gm program GraphicsMagick 1.3.35 2020-02-23 Q16 as found in Ubuntu 20.04.
• (optional) GNU parallel, in case you want to parallelize the gm work.

Caveats

• All dimensions are in pixels.
• If you use rotation, the image directory must be writable, and slashes in your filenames will break the temporary-rotated-image mechanism.
• It might break if you have spaces or quotes in your filenames. Don't do that.
• The drawing process might break if the command lines get too long, but the gm draw commands can be put into a text file, so it would be an easy fix.

Usage

There are 3 basic steps:

1. Generate a YAML description of the dimensions of each input file. This is a simple shell wrapper around gm identify. The input files are structured just like input to opcut, but guillot-calc only pays attention to the items section.

    $ guillot-prep.sh *.png > input.yaml

2. Fit these images into some fixed page size. Could take a very long time. The verbose output is mostly useful for knowing that it is still working and making a guess as to when it will finish.

    $ guillot-calc.rb --help
    Usage: guillot-calc.rb [options]
        -i, --input FILE                 [Mandatory] YAML input filename
        -g, --geometry WxH               [Mandatory] Page geometry in pixels
        -v, --[no-]verbose               [default: false] Verbose output
        -r, --[no-]rotate                [default: false] Also try rotating each image 90'
        -s, --spacing PIXELS             [default: 0] Space between images
        -m, --margin PIXELS              [default: 0] Page margin
        -e, --enough FRACTION            [default: 1.0] (0.5 to 1.0) Stop searching whenever this fraction of target area is covered

    $ guillot-calc.rb -i input.yaml -g 8000x6000 -v > layout.yaml

3. Render the images on top of a template page. guillot-draw outputs command lines which you can run with e.g. GNU parallel.

    $ guillot-draw.rb --help
    Usage: guillot-draw.rb [options] | parallel -j <CORES>
        -l, --layout FILE                [Mandatory] YAML layout filename
        -t, --template TEMPLATE          [Mandatory] Page template image or gm expression
        -i, --[no-]image                 [default: true] Draw image
        -b, --border PIXELS              [default: 0] Width of black border around images
        -n, --[no-]filename              [default: false] Draw filename over each image
        -f, --fontsize PIXELS            [default: 120] Font size; implies -n

    $ guillot-draw.rb -l layout.yaml -t base_8000x6000.png | parallel -j 4

That's it! The output will be in page_*.png

Instead of a template filename, you could theoretically use a GraphicsMagick xc: input, e.g. -t '-size 8000x6000 -type Grayscale xc:white', but my GraphicsMagick doesn't seem to support xc:.