pngnq-s9 Icon


A modified pngnq: convert png images to 256 colours.

5.0 Stars (3)
25 Downloads (This Week)
Last Update:
Download pngnq-s9-2.0.2.tar.gz
Browse All Files
Windows BSD Linux


pngnq-s9 is a modified version of pngnq, the neural network colour quantizer for png images.

Like pngnq, pngnq-s9 takes a full 32 bit RGBA png image, selects a palette of up to 256 colours, and then redraws the image in 8 bit indexed mode. The resulting image can be up to 70% smaller than the original.

pngnq-s9 adds several new options to pngnq including the ability to augment a user-supplied palette, the ability to quantize in the YUV colour space, and the ability to give more or less weight to specific colour components when quantizing. The program also includes a few bug fixes relative to the most recent version of pngnq.

The .tar.gz files have been known to compile on Unix type systems, including Cygwin. The only external dependencies are libpng and zlib.

For Windows users, we have a 32 bit binary, in, that should run as is on most modern Windows machines.

pngnq-s9 Web Site


Graphics Conversion


  • Quantizes 32 bit RGBA png images down to 256 colours or fewer, just like pngnq.
  • selectable internal colour space (either RGBA or YUVA)
  • use different sensitivities for each colour component
  • supply your own fixed palette, and optionally select additional colours as well. Very useful if you need particular colours to remain stable.
  • better colour selection through longer learning and improved rejection of duplicate colours
  • various options to alter colour selection policy (see -x, -u)
  • options to stop alpha values of 0 and 255 being 'smudged' to nearby values
  • selectable level of Floyd-Steinberg style dithering
  • suppresses writing of png gAMA chunk by default
  • suppresses writing of png background colour chunk
  • bug fix for occasional remapping to the wrong colour (relative to pngnq 1.1)
  • bug fix for a relatively harmless flaw in implementation of Floyd-Steinberg dithering (relative to pngnq 1.1)


User Ratings

ease 1 of 5 2 of 5 3 of 5 4 of 5 5 of 5 0 / 5
features 1 of 5 2 of 5 3 of 5 4 of 5 5 of 5 0 / 5
design 1 of 5 2 of 5 3 of 5 4 of 5 5 of 5 0 / 5
support 1 of 5 2 of 5 3 of 5 4 of 5 5 of 5 0 / 5
Write a Review

User Reviews

There are no 2 star reviews.

Additional Project Details

Programming Language




Thanks for helping keep SourceForge clean.

Screenshot instructions:
Red Hat Linux   Ubuntu

Click URL instructions:
Right-click on ad, choose "Copy Link", then paste here →
(This may not be possible with some types of ads)

More information about our ad policies

Briefly describe the problem (required):

Upload screenshot of ad (required):
Select a file, or drag & drop file here.

Please provide the ad click URL, if possible:

Get latest updates about Open Source Projects, Conferences and News.

Sign up for the SourceForge newsletter:

No, thanks