node-jpeg-mosher

Pure JS CLI that mildly corrupts JPEGs for a moshing-like effect; e.g. introduces creative distortions into the image data.

All Credit goes to knobs-dials, who wrote the original in python (https://github.com/knobs-dials/jpeg-mosh/), and did a lot of interesting research. It's available live at https://mosh.scarfboy.com/.

The test.jpg is from https://commons.wikimedia.org/wiki/File:Jpeg_thumb_artifacts_test.jpg

Requirements

• Node.js v14+ (uses native ES modules and promises)
• The ability to tolerate bad software

Installation

1. Clone this repository or download the script.
2. Run npm install to install the necessary dependencies.

Usage

Options

• --output, -o: Path to save the moshed JPEG file. (Default: moshed_image.jpg)
• --number, -n: Number of files to mosh. (Default: 1)
• --iterations, -i: Number of iterations to run the moshing process. (Default: 3)

Example

Mosh multiple JPEG files:

node index.js input.jpg -n 3 -o moshed_output.jpg

This command applies the mosh effect to the input.jpg file, saves the output as moshed_output.jpg, and processes the image three times (moshed_output-1.jpg, ...). The original file is not modified.

Notes

Some interesting reading:
- https://helpful.knobs-dials.com/index.php/Image_file_format_notes#Notes_on_JPEG_file_structure
- http://www.opennet.ru/docs/formats/jpeg.txt
- http://www.tex.ac.uk/ctan/support/jpeg2ps/readjpeg.c
- https://svn.xiph.org/experimental/giles/jpegdump.c
- http://fotoforensics.com/tutorial-estq.php  'estimating quality based on quantization tables"
- http://en.wikibooks.org/wiki/JPEG_-_Idea_and_Practice/The_header_part
- http://www.digitalpreservation.gov/formats/fdd/fdd000017.shtml
- https://web.archive.org/web/20240406182506/https://koushtav.me/jpeg/tutorial/2017/11/25/lets-write-a-simple-jpeg-library-part-1/