Shrink Ray

Whether in an electronic library or an electronic file folder, PDF documents are ubiquitous. These digital documents can quickly eat up your disk space or fill up your cloud storage. Minuimus [1], a Perl script, helps you reduce PDF file sizes to free up space while preserving file quality.

Installation

You can download the current version, Minuimus v3.7.1, from the project page [2]. First unpack the ZIP file and then run the following commands one after the other:

sudo make deps
sudo make all
sudo make install

The first call checks the dependencies and installs any missing programs. The second command creates the required Minuimus files, and the third command copies them to the /usr/bin/ directory. Upon completion, Minuimus will be available for all system users.

If you don't get the results you want with Minuimus's default settings, you can try one of the Minuimus options for potentially better results. Enter

minuimus.pl --help

to see a list of all the available options.

Operating Principle

The principle behind Minuimus is simple: Minuimus first decompresses a PDF file and then recompresses it more efficiently. Minuimus draws on its own capabilities as well as a number of other programs, including AdvanceCOMP [3] for compressing specific file types, OptiPNG [4] for compressing PNG images, Jpegoptim [5] for compressing JPEG files, Gifsicle [6] and flexiGIF [7] for compressing GIF files, and Qpdf Tools [8] for converting PDFs.

It is difficult to predict how much Minuimus will shrink your PDFs. It depends on several factors, including primarily how effective the original program was at creating the PDF file in question and how much reduction potential is left for Minuimus. If the PDF file only consists of text, there is little potential for file size reduction. The situation is different if the PDF contains many graphics and images, because they usually offer plenty of downsizing potential.

Another program similar to Minuimus is Leanify [9]. If Leanify exists on your computer, Minuimus will also use it as a helper; the two programs complement each other with their capabilities. This combination gives you even better results.

By default, Minuimus is lossless: It does not reduce the quality of images in the PDF file, but simply optimizes the compression. However, a slight loss of quality is sometimes acceptable if it results in smaller files. The following command

minuimus.pl --jpg-webp FILE.pdf

converts the JPEGs in the document to the leaner WebP format, reducing the quality of the images to 90 percent.

Minuimus in Use

After installation, call Minuimus with the command:

minuimus.pl FILE.pdf

I first tested Minuimus on the December 2022 community edition of LinuxUser (a German magazine) [10]. As shown in Figure 1, the file size was reduced from 12.7 to 11.2MB (about 88 percent of the original size). A loss of quality was not noticeable, especially with the images. The original metadata were also preserved.

Figure 1: How much Minuimus can shrink a file varies: These two files were reduced to 88 and 99 percent of their original sizes, respectively.

When I compressed the e-paper with the full version of the December 2022 issue of LinuxUser, the results were similar. Minuimus reduced the size of the PDF from 32.8 to 28.7MB (87.5 percent of the original size). I also tried out Minuimus on a scan from the Internet Archive of Arthur Conan Doyle's famous 1902 Sherlock Holmes novel The Hound of the Baskervilles [11]. In this instance, Minuimus only managed to reduce the file size to just under 99 percent of the original (12.3 to 12.1MB). Compared to this, Minuimus shrank a book I had scanned myself from 82.7 to 66.9MB (about 81 percent of the original size). Figure 2 shows the results for all four tests.

Figure 2: Minuimus' results depend on various factors and turn out differently every time. Here you can see the file sizes before and after processing for the four tests.