There are many types of different image formats and some of those most commonly found on the Internet are JPEG, GIF, BMP, TIFF and PNG. Each image format has its own purpose such as GIF is used for animated images, JPEG for high quality photos which automatically gets degraded after each save or even a resize, while our favorite PNG is best used on small and transparent pictures. Another huge advantage in PNG files is they're lossless meaning you can compress PNG's without losing quality.
You can easily find many tools on the Internet to compress PNG files but most, if not all of them produce different file sizes due to the algorithm unless they are using the same library/technology. Reducing the image file size to the maximum helps to save bandwidth cost, time to download and even achieving a higher Google PageSpeed score because 'optimize images' is one of the priorities. In this article we've put 13 free PNG compressor tools (online, command line, desktop) to the test to find the one that produces the smallest file size.
Two 8-bit and 24-bit PNG files are compressed using the 13 free image compression tools listed below. The list consists of command line tools, desktop programs and online services. Command line tools are more flexible for automation in batch files but require you to type in the full command including option switches and path. A desktop tool is an easier to use program with a graphical user interface that normally requires a few mouse clicks to work. Finally online services are applications hosted on remote servers where the processing is done on the server and the user doesn't need to install any third party software.To view the compression test results and summary, they can be found on page 2.
Easy, repeating the same optimization process in Photoshop is tedious and time-wasting. Now, you can make use of 'Actions' feature in Adobe Photoshop and batch save for web. Batch save for web step by step. Step 1: Get all of your images ready in a folder. Create a new folder with a name like 'image-compressed'. Caesium is a free, open source, advanced compression tool for photos and images (JPG, PNG, GIF), supporting batch, preview and many more. Caesium saves space and makes uploads faster. Download Image Optimizer for Windows to prepare JPEG, GIF & PNG image files for the web. Crop, Sharpen, E- Mail and Scanner & Digital camera interface and a Batch Wizard for compressing. Returns the current weights of the optimizer. The weights of an optimizer are its state (ie, variables). This function returns the weight values associated with this optimizer as a list of Numpy arrays. The first value is always the iterations count of the optimizer, followed by the optimizer's state variables in the order they were created. Comfortable batch processing Since Ashampoo Photo Optimizer 8 does so much fully automatically, we've included batch processing to save you time and nerves while the program processes your entire photo library in one go. Select individual images from various sources or entire folders and have Photo Optimizer work its magic.
Command Line Tools
1. advpng
advpng is part of AdvanceCOMP that contains multiple free utilities to recompress PNG, ZIP, MNG and GZ files. advpng hasn't been updated since 2005 but the compression speed and results will surprise you. Older machines with slower hardware specifications takes slightly longer to process while the newer multi-core CPU takes only a second to produce amazing results.
advpng maximum compression command:
advpng.exe -z4 file.png
Download AdvanceCOMP
2. OptiPNG
OptiPNG is another open source command line PNG compressor that supports Windows and Linux operating system. Both stable and development versions are available to download. Do take note that the maximum command line compression for the stable and development versions are slightly different. The highest level of compression for the OptiPNG stable is -o7 while the development is only -o6. If you try to force -o7 on the development build, you will still get the same file size as -o6.
OptiPNG stable maximum compression command:
optipng.exe -o7 file.png
OptiPNG development maximum compression command:
optipng-hg-latest-win32 -o6 file.png
Download OptiPNG
3. Pngcrush
Pngcrush is also a commandline application that attempts to optimize PNG images by trying out different compression levels and PNG filter methods. If you use the -brute switch, Pngcrush will test the image with 148 methods to find the one that gives the best compression.
Pngcrush maximum compression command:
Pngcrush.exe -brute file.png output.png
Download Pngcrush
4. PngOptimizerCL
PngOptimizer comes with a simple graphical user interface program and all you need to do is drag the images that you want to compress to the program's window, and also a command line application that runs in command prompt. Other than cleaning up wrong/useless information on PNG to reduce the file size, it can also support animated PNG format (apng) which is still uncommon today. You can either specify the exact file name to optimize or can even use the asterisk character as a wildcard.
PngOptimizerCL maximum compression command:
PngOptimizerCL.exe -file:'file.png'
Download PngOptimizerCL
5. PNGOUT
Unlike most of the command line PNG optimizers, PNGOUT is not open source because the compression algorithm is incorporated into their commercial GUI version called PNGOUTWin that has batch processing and multi-core CPU support. Although it is not open source, you can find pre-compiled binaries for Windows, Linux, BSD and Mac OS X. PNGOUT is one of the easiest to use because by default it uses the highest Xtreme compression algorithm for optimization without specifying an additional command line switch. Melody plugin vst.
PNGOUT maximum compression command:
Watchtower library twi. pngout.exe file.png
Download PNGOUT
6. ScriptPNG
ScriptPNG is actually a batch file that is capable of running up to 10 PNG compressors to optimize an image file. Selecting the ultra brute option number 9 will use the maximum compression options to produce the smallest file size but taking more time to complete the optimization process. All you need to do is drag and drop your PNG files to the program from Explorer and followed by selecting one of the 9 available options.
Download ScriptPNG
7. TruePNG
TruePNG only supports PNG files unlike some of the PNG compressors above that can attempt to convert other image formats such as JPEG and GIF into PNG if it is able to achieve a smaller file size.
TruePNG maximum compression command:
TruePNG.exe input.png /o max
Download TruePNG
Desktop Software
8. PNGGauntlet
PNGGauntlet is actually a front-end tool that uses 3 different PNG optimizers (PNGOUT, OptiPNG, and DeflOpt) to further compress PNG files instead of normally using just 1. The usage of 3 compressors does increase the time taken to compress the PNG files but definitely yields a smaller file size. A nice feature found in PNGGauntlet is the ability to automatically queue multiple files for batch processing. The default options from the Tools menu are already best (maximum) settings unless you want to preserve the PNG metadata, use grayscale color type and etc. Microsoft .NET Framework 4 is required to run.
Download PNGGauntlet
12Next › View AllBatch Image Optimizer
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I originally used PngGauntlet for everything, but recently that program bricked itself on my Windows 10 laptop [read: within the past week]; any attempt to launch it leads to absolutely nothing happening, not even an error message. Reinstalling the program, updating and reinstalling .NET, and even reinstalling Windows system components did not help. Running as Administrator, running in compatibility mode, double clicking the executable itself and double checking the shortcuts did not help either.
I really wish the creator of the software would actually update the stupid thing. In the meantime, if anybody has a backup download/installation link for ScriptPNG, I would really appreciate it.
ReplyI've updated the ScriptPNG link with the latest download I could find from 2016.
PNGGauntlet works fine here on the latest Win 10 32-bit and 64-bit. Could be an issue specific to you. The developer hasn't updated the program since 2012 so I doubt if anything new will be released now. Sadly it's not open source so nobody else can carry on the project.
ReplyThis is Quant – >>> pngquant.org/
And this is Gaundlet ->>> pnggauntlet.com/
The bad thing is that Gaundlet takes a lot of time 20m+
From my tests the best format is quant – > gaundlet – > quant with the follwing results:
stage0 – original ~ 15.455mb
stage1 – quantonly ~ 5.456mb
stage2 – quantgaundlet ~ 5.246mb
stage3 – quantgaundletquant ~ 4.797mb – From my point of view this is the best variant conv. time/quality
stage3.1 – quantgaundletquantgaundlet ~ 4.630mb
stage3.2 – quantgaundletquantgaundletquant ~ 4.427mb
stage3.3 – quantgaundletquantgaundletquantgaundlet ~ 4.268mb
stage3.4 – quantgaundletquantgaundletquantgaundletquant ~ 4.180mb
stage3.5 – quantgaundletquantgaundletquantgaundletquantgaundlet ~ 4.028
The other way around with gaundlet first is WORST, a lot of TIME is lost for nothing for example stage 2 is equal with stage 6 and stage 6 takes 40 minutes
stage4 – gaundletonly ~ 12.703mb
stage5 – gaundletquant ~ 5.456mb
stage6 – gaundletquantgandlet ~ 5246mb
CompressPNG.com, when it is online, compresses up to 20 images at a time, and allows you to the compression (colour count) if the file is sill too large.
I don't work for them, but have compressed 1000's with them.
The optimizers are often impractically slow when dealing with large images that aren't expected to be viewed that many times. 24-bit truecolor screenshots with sharp edges, especially where fonts don't have anti-aliasing, can typically be reduced in size by switching off PNG prediction (none, sub, paeth). If your imageset is a guide/review with most images of this kind, then you can batch convert all of them in FastStone Image Viewer and improve their size and decoding speed. Sometimes scans without any transparency get saved as a layer with alpha by some software. They can be made smaller by flattening the image to background beforehand.
ReplyWell this was not good at all! I just wasted 15 hours of compressing PNG files with PNGAUNTLET and FileOptimizer, only to see Googles Page Speed still complaining about compression. So I checked a file, and either PNGAUNTLET or Fileoptimizer reduzed my 400kb PNG by a single byte! So I downloaded one of the other tools PNG Optimizer, same there. This PNG doesnt seem to compress with windows compression tools.
I tried the compressor.io website and it compresses the image by 90% wooosh… Fuck!
I am beginning to think that none of the windows apps are updated and are running old compression algorythms. I will download and check out one of the dos tools you have here since I post this, but if I do not come with an update after this post consider the windows tools useless by todays standards.
Kim Steinhaug
Replythanks!
ReplyScriptPng worked best for my 20k photos. I tried them all.
CPUS will take a pounding at 100% for days if using 8 cores under. I switched to a super computer (4) e78860s a few hours it was done but not before I was sweating and my hearing went deaf from the turbo fans kicking in. If you use the above scriptPNG you should use
1) CPUID HWMonitor – MONITORS CPU TEMPS MUST HAVE
2) SpeedFan by almico.com/speedfan.php – configures temps of CPU/GPU etc
All in all watch those temps NOT the CPU at 100%. its the temps that will kill your comp.
Not for newbies! But works great under these conditions.
ReplyI'm pretty sure TinyPNG is using PNGoo with 128 colors, dithered based on the file size. I would have just used TinyPNG but I needed to work on ~1000 images.
With the simple images (charts) I was working with, I couldn't really see any difference in the quality from the original ~500k image, the ~400k lossless compressed image from PNGGauntlet, and the ~200k lossy image from PNGGoo. I was able to eek out a few more K (~6%) by running first through PNGoo (128 colors, no dithering) and then through PNGGauntlet. Real numbers example: 581k -> 168k -> 157k (72% total decrease!)
ReplyGreat list! You may check out resizeimage.net too, it can resize and optimize images in one step.
ReplyHi Reymond,
I love your comparison articles – please keep them up!
I have done my own image compression comparison, and would love if you could have a peak in it.
myblog.chaiware.org/2013/09/best-lossless-image-size-reduction.html
I have signed up to your RSS.
ReplyThanks for sharing, Raymond
I'll try pngout for Mac OS X, it seems interesting.
I currently use compresspng to optimize. It is a fantastic online tool.
Nyc i am using pngout it consume processor so much during compression
ReplyTwo other programs of interest:
* RIOT is useful to cut down on unnecessary extra colors ahead of additional compression. If the image looks the same to you with only 16 colors as with 256, that's a big size difference.
* FileOptimizer – although it's just a front end for some of the programs already discussed above
* Png Optimizer psydk.org/PngOptimizer.php probably not the same compression level, but will compress animated PNG files (APNG).
RIOT is a great plugin for irfanview
Replythanks Raymond for this info :)
ReplyThanks for the update!
Replythanks a lot Raymond! just what i was looking for. pngout is really good. only thing lags is transparent color. but it is awesome that how this can save lot of bandwidth. really helpful post. thanks again.
Replythanks!! it help me alot.
ReplyThanks mate!
Replythx ray~
ReplyPNG is the best image format in saving bandwidth :D Now you can crush it summore… Bluebeam ipad crash.
Image Optimizer Pc
ReplyBatch Image Optimizer App
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