README.md

sqlite-phhammdist

PHash Hamming distance calcuation in SQLite

sqlite-phhammdist - Hamming distance between two UINT64 TEXT string in SQLite returned as an INT

Synopsis

This SQLite extension adds a function phhammdist() to SQLite. phhammdist() takes two unsigned 64bit integer in TEXT string as arguments and returns the Hamming distance as an integer, as per the pHash cpp implementation.

Usage

To load the extension into an open SQLite database, run the following queries:

  SELECT load_extension('/path/to/sqlite-phhammdist.so', 'sqlite3_phhammdist_init');

You can then use the function in SQL queries, for example to find photos which have a perceptual hash that is close in Hamming distance:

  SELECT photo_id, phhammdist(photo_hash, ?) AS ph_dist FROM photos WHERE ph_dist <= 9;

When loading extensions from python, the python binary needs to be built with the --enable-loadable-sqlite-extensions configure argument. You then need to enable the loading of extensions using:

  dbconn.enable_load_extension(True)

After that, you can issue the above SELECT statement to load the extension.

Inspiration

Inspiration for this comes from:

https://github.com/droe/sqlite-hexhammdist
Hamming Distance calcation in SQL Lite using hex representations from Daniel Roethlisberger

https://gist.github.com/kylelk/39fed416b0125dbbe62e
Population bit count calcuation in SQL Lite from kyle kersey

https://gitlab.com/opennota/findimagedupes
Find image duplicates written in golang from opennota