Image compression and decompression using SVD

Installation

Install CLI using pipx:

pipx install git+https://github.com/toadharvard/svdi-cli.git

Or

pipx install svdi

Usage example

svdi compress --in-file=images/rafiq.bmp --out-file=images/liquidated.svdi --compression=3 --method=numpy

svdi decompress --in-file=images/liquidated.svdi --out-file=images/rafiq2.bmp

ls -l ./images

Available SVD functions

1. rsvd — N Halko, P. G Martinsson, and J. A Tropp. Finding structure with randomness: Probabilistic algorithms for constructing approximate matrix decompositions. Siam Review, 53(2):217-288, 2011.
2. numpy — NumPy's np.linalg.svd function.
3. pcafast — H. Li, G. C. Linderman, A. Szlam, K. P. Stanton, Y. Kluger, and M. Tygert. Algorithm 971: An implementation of a randomized algorithm for principal component analysis. Acm Transactions on Mathematical Software, 43(3):1-14, 2017.
4. pi — Power iterations method. URL: http://www.cs.yale.edu/homes/el327/datamining2013aFiles/07_singular_value_decomposition.pdf

Available commands

svdi --help
svdi compress --help
svdi decompress --help

SVDI Format

The CLI uses a simple binary format for storing SVD results in .svdi files.

Each .svdi file consists of a header followed by the SVD results for each channel:

1. Header
   1. Signature: A fixed 4-byte sequence b'SVDI' to identify the file format.
   2. Dimensions: Three 4-byte unsigned integers representing the shape of the matrices: m, n, and k.
      • m: The number of rows in each U matrix.
      • n: The number of columns in each Vh matrix.
      • k: The size of each S vector, and the number of columns in U and rows in Vh.
2. Channel Data Repeated for each channel (NUMBER_OF_CHANNELS):
   • U Matrix: A matrix of size m * k, with elements stored as 32-bit floats in row-major order.
   • S Vector: A vector of length k, with elements stored as 32-bit floats.
   • Vh Matrix: A matrix of size k * n, with elements stored as 32-bit floats in row-major order.

Licence

See the details of the license in the LICENCE file.