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Compress Seg

Library for compressing and decompressing image segmentation (adapted from neuroglancer)

import compressed_segmentation as cseg

sx, sy, sz = (128,128,128)
dtype = np.uint64
order = 'C'

labels = np.arange(0, sx*sy*sz, dtype=dtype).reshape((sx,sy,sz), order=order)
compressed = cseg.compress(labels, order=order)
recovered = cseg.decompress(
    compressed, (sx,sy,sz) dtype=dtype, order=order
)

arr = CompressedSegmentationArray(
    compressed, shape=(sx,sy,sz), dtype=dtype
)
label = arr[54,32,103] # random access to single voxels w/o decompressing
uniq_labels = arr.labels() # get all distinct values w/o decompressing
binary2 = arr.remap({ 1: 2 }, preserve_missing_labels=False) # remap labels in segmentation w/o decompressing
recovered = arr.numpy() # decompress to a numpy array, same as decompress
124213 in arr # test if a value is in the array

cseg compress connectomics.npy
cseg decompress connectomics.npy.cseg --volume-size 512,512,512 --bytes 4

NOTE: This repository is the PyPI distribution repo but is based on work done by Jeremy Maitin-Shepard (Google), Stephen Plaza (Janelia Research Campus), and William Silversmith (Princeton) here: https://github.com/janelia-flyem/compressedseg

This library contains routined to decompress and compress segmentation and to manipulate compressed segmentation data defined by the neuroglancer project. compressed_segmentation essentially renumbers large bit width labels to smaller ones in chunks. This provides for large reductions in memory usage and higher compression.

Note that limitations in the compressed_segmentation format restrict the size of the chunk that can be compressed. As this limitation is data dependent, for example a random array with 1024 labels passes testing at 256x256x128, but 256x256x256 often does not.

Features

• Compression and decompression
• Random access to voxels without decompression
• Read out unique values without decompression
• Remap labels without decompression
• Command line interface for numpy files
• (TBD) Interface to relabel and manipulate segmentation from the compressed data
• C++, Python, and Go interface (see original repo for Golang)

C++ Compilation

Compiling as a shared library. Feel free to subsititute e.g. clang for the C++ compiler.

g++ -std=c++11 -O3 -fPIC -shared -I./include src/compress_segmentation.cc src/decompress_segmentation.cc -o compress_segmentation.so

Python Installation

pip Binary Installation

$ pip install compressed-segmentation

$ python
>>> import compressed_segmentation as cseg
>>> help(cseg)

If there are pre-built binaries available for your architecture this should just work.

pip Source Installation

If you need to build from source, you will need to have a C++ compiler installed:

$ sudo apt-get install g++ python3-dev 
$ pip install numpy
$ pip install compressed-segmentation

$ python
>>> import compressed_segmentation as cseg
>>> help(cseg)

Direct Installation

Requires a C++ compiler such as g++ or clang.

Works with both Python 2 and 3. Encodes from / decodes to 3D or 4D numpy ndarrays.

$ sudo apt-get install g++ python3-dev 
$ pip install -r requirements.txt
$ python setup.py install

$ python
>>> import compressed_segmentation as cseg
>>> help(cseg)

License

Please see the licenses in this repo.