Pure Python library for PNG image encoding/decoding
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Latest commit f5c4c76 May 18, 2016
drj11 committed May 18, 2016 Fixing palette alpha forcing
Thanks to Scondo





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PNG module for Python. PyPNG is written entirely in Python.


import png
png.from_array([[255, 0, 0, 255],
                [0, 255, 255, 0]], 'L').save("small_smiley.png")

After that, try import png then help(png). Also, lickable HTML documentation appears in the html/ directory. If HTML is no good then you could try the ReST sources in the man/ directory.


PyPNG is pure Python and has no dependencies. It requires either Python 2.6 or Python 3.4 or any compatible higher version. The same code runs in both Python 2.x and Python 3.x.

PyPNG comes with a setup.py script to use with distutils. After unpacking the distribution, cd into the directory and execute the command:

python setup.py install

The png module will be installed; import png will allow you to use it from your Python programs.

Alternatively, you can copy code/png.py wherever you like. It's intended that you can copy png.py into your application and distribute it. The following curl command should copy the latest version into your current directory:

curl -LO https://raw.github.com/drj11/pypng/master/code/png.py


(For issues see https://github.com/drj11/pypng/issues?state=open )

Release (Not yet released)

Support for earlier versions of Python is dropped in order to simplify the code. From the 2.x series only Python 2.6 and 2.7 are supported. From the Python 3.x series all versions from 3.2 onward are supported.

Release 0.0.18

Thanks to github.com/sean-duffy, .from_array() can now take a 3D array.

Converting to PNMs was broken in Python 3; this is now fixed. Github issue 26: https://github.com/drj11/pypng/issues/26

Release 0.0.17

Various fixes when running on Python 3 and Windows. Merging pull requests from github.com/ironfroggy and github.com/techtonik, and merging by hand a commit from github.com/Scondo.

Release 0.0.16

Compatible with nose: nosetests png.py now works.

Allow any "file-like" object as an input.

Handle newlines in texttopng.

Release 0.0.15

Fixed various URLs to point at github.com instead of googlecode.

Release 0.0.14

When using png.py as a command line tool, it can now produce non-square test images.

PyPNG now installs "out of the box" on Python 3 on a plain install (previously distribute or pip was required).

PyPNG welcomes the following community contributions:

Joaquín Cuenca Abela speeds up PNG reading when Cython is available.

Josh Bleecher Snyder adds a lenient mode which has relaxed checksum checking.

nathan@dunfield.info fixed a problem writing files when using the command line tool on Windows (Issue 62).

The following issues have been fixed:

On github:

Issue 6: Palette processing is annoying

On googlecode:

Issue 62: Problem writing PNG files on Windows

Development has moved from googlecode to github. All issues below here, and the one immediately above, are from the googlecode issue tracker. All newer issue should be on github.

Release 0.0.13

PyPNG now installs "out of the box" on Python 3. Thanks to simon.sapin@kozea.fr and nathan@dunfield.info for the patch.

The following issues have been fixed:

Issue 63: setup.py does not use 2to3 Issue 64: Typo in documentation

Release 0.0.12

PyPNG now works on Python 3 if you use the 2to3 tool. Fix for converting grey images to RGBA.

The following issues have been fixed:

Issue 60: Greyscale images not properly being converted to RGBA Issue 61: Doesn't work on Python 3

Release 0.0.11

Added the "How Fast is PyPNG" section to the documentation. Changed it so that more PNG formats return their rows as Python array.array instances.

Release 0.0.10

Fix for read_flat method (broken for ages).

The following issues have been fixed:

Issue 56: read_flat broken

Release 0.0.9

Tentative fix for a deprecation warning on 64-bit Python 2.5 systems. Conversion tool for Plan 9 images.

Issue 54 (below) is tentative. The PyPNG developers have been unable to reproduce the error (as it seems to be on 64-bit Python 2.5 systems); any user reports would be most welcome.

The following issues have been fixed:

Issue 54: Deprecation warnings when using pypng. Issue 55: Cannot convert Plan 9 images.

Release 0.0.8

Mostly more robust to dodgy input PNGs, as a result of testing with brokensuite. One fixed bug was a critical: an infinite loop for a least one input (Issue 52 below).

The following issues have been fixed:

Issue 47: Leading blanks when using write_packed. Issue 48: pipdither fails when input has no gamma chunk. Issue 49: pipdither fail with 1-bit input. Issue 50: pipchunk adds second gamma chunk. Issue 51: piprgb and pipasgrey fail for color mapped images. Issue 52: Some inputs cause infinite loop.

Release 0.0.7

Better documentation (in html/ex.html mostly) for NumPy integration.

The following issues have been fixed:

Issue 46: Unclear how to get PNG pixel data into and out of NumPy.

Release 0.0.6

NumPy integer types now work.

The following issues have been fixed:

Issue 44: Cannot use numpy.uint16 for pixel values.

Release 0.0.5

sBIT chunks are now handled, meaning that PyPNG can handle any (single) bit depth from 1 to 16 from end to end.

The following issues have been fixed:

Issue 28: Does not add sBIT chunk. Issue 36: Ignores sBIT chunk when present.

Release 0.0.4

PyPNG now works on Python 2.2 (significant for Symbian users as PyS60 is based on Python 2.2). Not all features are supported on Python 2.2.

The following issues have been fixed:

Issue 16: Source and doc uses 'K' where it should use 'L'. Issue 32: Does not accept packed data. Issue 33: Cannot create greyscale PNG with transparency. Issue 35: Does not work on Python 2.2.

Release 0.0.3

Handling PAM files allows end to end handling of alpha channels in workflows that involve both Netpbm formats and PNG. PyPNG now works in Python 2.3.

The following issues have been fixed:

Issue 14: Does not read PAM files. Issue 15: Does not write PAM files. Issue 25: Incorrect handling of tRNS chunk. Issue 26: asRGBA8 method crashes out for color type 2 images. Issue 27: Fails on Python 2.3.

Release 0.0.2

Lickable HTML documentation is now provided (see the html/ directory), generated by Sphinx.

The following issues have been fixed:

Issue 8: Documentation is not lickable. Issue 9: Advantage over PIL is not clear. Issue 19: Bogus message for PNM inputs with unsupported maxval Issue 20: Cannot write large PNG files

Release 0.0.1

Stuff happened.


  • .../ - top-level crud (like this README, and setup.py).
  • .../code/ - the Python code.
  • .../html/ - lickable manuals (generated).
  • .../man/ - manuals (in source/plain-text).
  • .../proc/ - documented procedures (release procedure).