PNG Tools Overview

You can find a lot of PNG Tools on the net. This article list them, and show competitors running with right settings for maximize the compression. To see why results are Good, Correct, Bad, or to see images tested, read this article : PNG Compression Tools Comparison.

AdvanceCOMP

advancecomp v1.15 by Andrea Mazzoleni
Usage: advpng [options] [FILES...]

Options:
  -0, --shrink-store    Don't compress
  -1, --shrink-fast     Compress fast
  -2, --shrink-normal   Compress normal
  -3, --shrink-extra    Compress extra
  -4, --shrink-insane   Compress extreme

Version : 1.15 | See Website | Download AdvanceCOMP (Win32)

This project is not updated since 2002. Despite that, it can give some interesting results. It contains two seperate programs, advdef and advpng. First one recompress the deflate stream, second can do some image structure modifications before compression (remove unnecessary chunks, compact iDAT, 8 bits/pixels test).

advpng is a compressor tool, which can do a 7-zip re-compression in a very fast process. It does not support GrayScale files, image reduction, or others optimization tricks. It has no option for better results. For an efficient usage of advpng, you should optimize your PNG files before, and compress them next with it.

CryoPNG

OptiPNG 0.6.4 (Dirty Filters Ugly Hack): Advanced PNG optimizer.
Copyright (C) 2001-2010 Cosmin Truta.

Synopsis:
    optipng [options] files ...
Files:
    Image files of type: PNG, BMP, GIF, PNM or TIFF
Optimization details:
        -o7  =  -zc1-9 -zm8-9 -zs0-3 -f0-5    (240 trials)

Version : 0.6.4 | See Website | Download CryoPNG (Win32)

This project is credited OptiPNG, it's true name is CryoPNG, and it's created by Frederic Kayser. His idea was to apply filters to RGB data which are not displayed by browser, instead of using always the 0 (None) Filter. CryoPNG is only applicable on RGB+Alpha files (ColorType 6), and is a modification of OptiPNG.

CryoPNG is a must have tool for a best filtering of RGB+Alpha PNG. It does not support all others ColorType, but it's very efficient in this category. For an efficient usage of cryopng, you should optimize your PNG32 files with it, but you have to complement it with another png optimizer.

OptiPNG

OptiPNG 0.6.5: Advanced PNG optimizer.
Copyright (C) 2001-2011 Cosmin Truta.

Synopsis:
    optipng [options] files ...
Files:
    Image files of type: PNG, BMP, GIF, PNM or TIFF
Optimization details:
        -o7  =  -zc1-9 -zm8-9 -zs0-3 -f0-5    (240 trials)

Version : 0.6.5 | See Website | Download OptiPNG (Win32)

This project is based on PNGCrush. According to the author, it's running faster because all trials are performed in memory. It also include part of PNGRewrite code for doing some images reduction. OptiPNG is used by a lot of optimizers, including online service as SmushIt.

OptiPNG is an soft optimizer, and run a good compression routine, but it should be more efficient if it runs others optimization tricks. It does not support RGB filtering, or other image reduction which can be very useful and efficient for Web.

PNGCrush

 | pngcrush 1.7.15
 |    Copyright (C) 1998-2002,2006-2011 Glenn Randers-Pehrson
 |    Portions copyright (C) 2005       Greg Roelofs

options:
    -bit_depth depth (bit_depth to use in output file)
        -brute (use brute-force: try 126 different methods [11-136])
            -c color_type of output file [0, 2, 4, or 6]
            -f user_filter [0-5]
      -huffman (use only zlib strategy 2, Huffman-only)
     -plte_len n (truncate unused entries from the top of PLTE)
       -reduce (do lossless color-type or bit-depth reduction)
            -z zlib_strategy [0, 1, 2, or 3]
         -zmem zlib_compression_mem_level [1-9, default 9]

Version : 1.7.15 | See Website | Download PNGCrush (Win32)

PNGCrush is one of the first PNG optimizer which have been publied, back in 1998. The author has also written the PNG specification and others cool projects on MNG. PNGCrush as a lot of options, and most of utils are based on it (OptiPNG, TruePNG, and indirectly all optimizers based on OptiPNG as SmushIt).

PNGCrush is probably the most know PNG opitimizer. As you can see, there is yet improvement to do to get better results and as PNGOUT, you have to know PNG basics knoweldge to use correctly. Others optimizers based on it have the advantage to search PNG settings automatically.

PNGOptimizer

PngOptimizerCL 2.0 (x86) (C) 2002/2011 by Hadrien Nilsson - psydk.org
Converts GIF, BMP and TGA files to optimized PNG files.
Optimizes and cleans PNG files.

Usage:  PngOptimizerCL -file:"yourfile.png"
  [-BackupOldPngFiles]
  [-KeepInterlacing]
  [-AvoidGreyWithSimpleTransparency]
  [-IgnoreAnimatedGifs]
  [-KeepFileDate]
  [-KeepBackgroundColor][:R|K|F] [-ForcedBackgroundColor:RRGGBB]
  [-KeepTextualData][:R|K|F]  [-ForcedTextKeyword:Foo] [-ForcedTextData:Bar]

Version : 2.0 | See Website | Download PNGOptimizer (Win32)

PNGOptimizer is the faster tool tested here. It runs a good optimization step before doing an average compression, supports some image reduction and can do RGB Filtering (only with None filter). It gives a good ratio speed performance / output result.

The very fast process of those files is a good point, there are still others image reduction and tweaks which can done. PNGOptimizer reduces all PNG Test Corpus files by more than 50%. It can be used as an optimizer, then run another compression routine to achieve better results.

PNGOUT

PNGOUT [In:{PNG,JPG,GIF,TGA,PCX,BMP}] (Out:PNG) (options...)      Jul  2 2011
by Ken Silverman (http://advsys.net/ken)
PNGOUT optimizes PNG size losslessly using my own deflate algorithm (not Zlib)
With the right options, it can often beat other programs by 5-10%. Options:
   /c# PNG output color: 0=Gray, 2=RGB, 3=Pal, 4=Gray+Alpha, 6=RGB+Alpha
   /f# PNG output filter: 0=none, 1=x, 2=y, 3=x&y, 4=Paeth, 5=mixed, 6=reuse
   /d# Override default bitdepth: 0(min),1,2,4,8 (valid only in /c0,/c3 modes)
   /s# Select strategy. 0:Xtreme(default), 1:Intense, 2:Longest Match,
       3:Huffman Only, 4:Uncompressed

Version : 07/02/2011 | See Website | Download PNGOUT (Win32)

PNGOUT is probably the best PNG Compressor (but not the best PNG optimizer for a Web usage). Users have to select right settings to get best results, so you must have PNG basics knoweldge before using it. As you can see in PNG Compression Tools Comparison, PNGOUT should be used with its options.

PNGOUT is a great compressor once you get the right settings. But for a Web usage, it should be interesting to use RGB filtering or Palette Optimization. PNGOUT is a must have tool for the final compression. You should be use it after a good PNG pre-optimizer to achieve a best result.

PNGRewrite

pngrewrite v1.4.0: PNG image palette optimizer
Usage: pngrewrite infile.png outfile.png

Version : 1.4.0 | See Website | Download PNGRewrite (Win32)

PNGRewrite does image reduction, mainly working with Palette images but not only. It can sort the palette (to get a small tRNS chunk), remove duplicates entries, trunk the palette, or try to reduce pixel depth or modify ColorType if possible. All thoses operations are lossless for the image.

PNGRewrite is good for Palette images, or images which can be converted to Palette without loss of quality (image reduction). In others cases, it's recommanded to use another optimizer in complement, because PNGRewrite only supports this kind of images.

pngwolf

-----------------------------------------------------------------------------
Usage: pngwolf --in=file.png --out=file.png
-----------------------------------------------------------------------------
 --zlib-level=                  zlib estimator compression level (default: 5)
 --zlib-strategy=               zlib estimator strategy (default: 0)
 --zlib-window=                 zlib estimator window bits (default: 15)
 --zlib-memlevel=               zlib estimator memory level (default: 8)
 --7zip-mfb=                    7zip fast bytes 3..258 (default: 258)
 --7zip-mpass=                  7zip passes 0..15 (d: 2; > ~ slower, smaller)
 --7zip-mmc                     7zip match finder cycles (d: 258)
 --normalize-alpha              For RGBA, make fully transparent pixels black
-----------------------------------------------------------------------------
Uses http://zlib.net/ and http://lancet.mit.edu/ga/ and http://www.7-zip.org/
-----------------------------------------------------------------------------
http://bjoern.hoehrmann.de/pngwolf/ (c) 2008-2011 http://bjoern.hoehrmann.de/

Version : March 2011 | See Website | Download pngwolf (Win32)

pngwolf is a great PNG optimizer, which have the ability to test differents filtering methods. According to its author, it uses a genetic algorithm for finding the best scanline filter for each scanline in the image. It's very efficient on RGB (24-bit) or RGB+Alpha (32-bit).

PNGWolf is an excellent tool which can be useful for all filtered images (including Filtered Paletted images). It does not support yet any image reduction (except RGB Filtering with None Filter). Combined with PNGOUT and -ks -f6 option, you can get good results.

TruePNG

TruePNG 0.3.5.4 : PNG Optimizer
by x128 (c) 2010-2012
x128@ua.fm

TruePNG {options} file

optimization level:
/o4 or /o max  = /zc9 /zm1-9 /zs0-3 /fe /i0 /md remove all

Version : 0.3.5.4 | See Website | Download TruePNG (Win32)

TruePNG is one of the best PNG optimizer (but not the best PNG compressor), because it can determine with the most accurate way the ColorType / Delta filtering adapted to the file. It also include a strong palette optimizer, and RGB filtering with several filters.

TruePNG is an excellent PNG optimizer, and can also achieve a best compression than OptiPNG because of a better PNG optimization (ColorType choice / Filtering). It can be completed with strongest compressor, as advdef, or PNGOUT with -ks -kp settings (for filtered Paletted files).

pngXoptimizer

pngXoptimizer 1.1 - by Cedric Louvrier

Drag-and-Drop your PNG files on pngXoptimizer executable

Version : 1.1 | See Website | Download pngXoptimizer (Win32)

pngXoptimizer is my homemade tool, a PNG batch optimizer which is able to combine an optimizer and a solid compressor with up to 4 parallel process (multi-threading). Most of the time, pngXoptimizer can give smallest files than others tools, and in a faster batch process.

Thanks to the tools, pngXoptimizer can optimize and reduce file significantly. It also contains instructions to optimize some files faster or better.

Other optimizers and PNG Quantizers