Home > PNG Tools Overview

PNG Tools Overview

AdvanceCOMP

See Website - Version tested: 1.15 - Type: Compressor

This project is no longer updated since 2002. AdvPNG is a pure compressor that uses LZMA (7-zip), and it operates some optimizations on the PNG characteristics (it removes unnecessary chunks, compacts iDAT, and tries 8 bits/pixels test when image contains 16 colors or less).

AdvPNG saved 50597 Bytes (5,36 %). To use to its advantage, you should run AdvDef (not AdvPNG) after another PNG optimizer utility, capable of performing tests on ColorType, filters, etc. Used alone, it is less efficient because it allows only a few images reductions, and it does not support GrayScale formats.

CryoPNG

See Website - Version tested: 0.6.4 - Type: RGB+Alpha optimizer

This project is credited OptiPNG, but it is actually a modification of OptiPNG, called CryoPNG. This utility can be used on TrueColor + Alpha PNG, and lets you change the RGB space of a PNG file in order to optimize the filtering. It can convert black pixels using existing filters.

CryoPNG saved 244701 Bytes (25,90 %). Although it can not process all files, CryoPNG can significantly reduce the weight, because it destroys (or changes) RGB values ​​that will not be returned in a Web browser. You can use it only on TrueColor + Alpha PNG, and can be supplemented by a compressor.

OptiPNG

See Website - Version tested: 0.6.5 - Type: Optimizer

This project is based on PNGCrush. According to the author, it's running faster because all trials are performed in memory. It also includes parts of PNGRewrite code for some images reductions. OptiPNG is used by a lot of optimizers, including onlines services as SmushIt.

OptiPNG saved 385335 Bytes (40,78 %). OptiPNG is a moderate 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 images reductions which can be very useful and efficient for Web.

PNGCrush

See Website - Version tested: 1.7.15 - Type: Optimizer

Pngcrush is one of the first optimization utilities for PNG, published in 1998. The author also wrote the specifications of PNG. PNGCrush has a lot of options, and most of tools are based on it (OptiPNG, TruePNG, and indirectly all optimizers based on OptiPNG as SmushIt).

PNGCrush saved 408652 Bytes (43,25 %). To correctly use pngcrush, you must know the PNG specification, and control options of the utility, because without them, it is unlikely to get a properly optimized PNG. Others optimizers have the advantage to do that automatically.

PNGOptimizer

See Website - Version tested: 2.0 - Type: Optimizer

PngOptimizer is a very simple tool to use: there is no option for images reductions, it does it itself automatically (clean RGB space, palette optimizer, bitdepth reduction, etc.), and also does an average compression. Another good point, it's generally fast.

PNGOptimizer saved 517229 Bytes (54,74 %). It reduces all PNG Test Corpus files by more than 50%. This tool includes most of the critical images reductions, but there is still more improvement to do to get even better results. It can be completed by a good compressor.

PNGOUT

See Website - Version tested: 07/02/2011 - Type: Compressor / Manual Optimizer

PNGOUT is undoubtedly the best PNG compressor, based on a modified algorithm of Deflate, called KFlate. It can also achieve images reductions, mainly manually. That's mean you've to know about PNG specifications to use it efficiently.

PNGOUT saved 410831 Bytes (43,48 %). The best usage of PNGOUT is to run it after a good PNG optimizer, as TruePNG. You can use it as a pure compressor, because PNGOUT does not operate some images reductions for Web, as the cleaning of RGB space.

PNGRewrite

See Website - Version tested: 1.4.0 - Type: Paletted/GrayScale Optimizer

PNGRewrite is command-line utility that reduces the unnecessarily large palettes that some programs write into PNG files. It also optimizes transparency data, and reduces the bits-per-pixel if possible. It only runs on Paletted or GrayScale images.

PNGRewrite saved 35838 Bytes (3,79 %), without any comparison to others utility: it only works on Paletted images. Most of PNGRewrite tricks are included into others tools, as OptiPNG, which is using its code. This tool is today partially obsolete.

PNGWolf

See Website - Version tested: March 2011 - Type: Optimizer

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 saved 524907 Bytes (55,56 %). It 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

See Website - Version tested: 0.4.0.3 - Type: Optimizer

If you have to choose one, TruePNG is the must have tool, because it operates the most of images reductions (i've returned a lot of suggestions to its author, based on PNG Test Corpus files). Completed with PNGOUT, it gives excellent results — this combinaison is used by ScriptPNG.

TruePNG saved 568193 Bytes (60,14 %). It does RGB space cleaning, palette optimization, ColorType best choice, BitDepth reduction, etc. Thanks to that, it also achieves the best compression results. You can use PNGOUT to compress files further, using -ks -f6 options.

Others Tools

DeflOpt

See Website - Type: Deflate Structure Optimizer

It removes garbage from PNG files, cleans huffman symbols and does others tricks to optimize the Deflate structure. A quick cleaner which can be efficient after a PNG optimizer, and a PNG compressor.

defluff

See Website - Type: Deflate Structure Optimizer

This tool is very closed to DeflOpt, and does the same things with different strategies. To get bests results, you can combine both of them, always after a PNG optimizer and when compression is achieved.

Huffmix

See Website - Type: Block code Optimizer for PNGOUT

Huffmix gets the best blocks results from two trials files created by PNGOUT, and creates a new output file with best results. It can let you to optimize trials results of PNGOUT.

PrePNG

See Website - Type: PNG Reset Tool

Prepng rewrite input PNG without compression, but with filtering step (delta, average, and Paeth). Setting no compression to a file can help to improve new trial compression.

pngquant

See Website - Type: Quantizer, converter to PNG Paletted

pngquant is a PNG quantizer. It reduces the number of colors to 256 or less. It always create PNG-8 files (Paletted), which can contains alpha values if necessary. See also pngnq.

pngnq

See Website - Type: Quantizer, converter to PNG Paletted

pngnq is based on pngquant, but it uses a different quantization algorithm which is more efficient, and give better quality / size ratio. Only produces PNG-8 (Palette images) with alpha values if necessary.

Color Quantizer

See Website - Type: Quantizer, Optimizer

Color Quantizer is a GUI which contains other programs, like PNGOUT, TruePNG, DeflOpt, jpegtran and Intel library for JPG. It can reduce the number of colors with an advanced quantizer.

PNGKT

See Website - Type: RGB Space Cleaner

PNGKT is a RGB Filter. It can optimize PNG files by turning to (0,0,0) all RGB pixels which are not displayed (because Alpha Channel corresponding pixels is also 0).