JPEGs optimization

[lena]

Hi all.

I have found these two papers:

• http://ieeexplore.ieee.org/iel5/83/4711346/04682736.pdf?arnumber=4682736
• http://ieeexplore.ieee.org/iel5/4378863/4379219/04379276.pdf?arnumber=4379276
  

which present a compression method fully compatible with existing JPEG decoders, that achieve a 30% reduction on file size without noticeable degradation and the method is quick (0.2 seconds for typical images).

It is also claimed that this algorithm achives the maximum compression that JPEG encoders fully compatible with existing JPEG decoders can achieve.

As photoshop does not have it, do you know if there is a software that implements this algorithm?

[pmeenan]

You couldn't have asked at a better time - this just rolled across TechCrunch: http://techcrunch.com/2011/09/06/new-sta...r-quality/

[lena]

(09-07-2011 02:21 AM)pmeenan Wrote:  You couldn't have asked at a better time - this just rolled across TechCrunch: http://techcrunch.com/2011/09/06/new-sta...r-quality/

I'm not sure that jpegmini is using those kind of "free" (i.e. encoding) optimizations (joint optimization of quantization table + run-length encoding + Huffman table). Last time I tried it, it seemed to me that it was optimizing the image, but not the encoding (+30% size reduction). I'll give it another try and see.

[pmeenan]

Yeah, I haven't seen any of the advanced optimizations applied to libjpeg (which is what just about everything except for Photoshop is based on). jpegtran can do some basic huffman table optimizations to squeeze a little space from images but not on the order of what the researchers were seeing.

[lena]

I believe that jpegmini is not using any optimization of quantization tables + run-length encoding + Huffman encoding, because by using optimized quantization tables alone I get images without visible artifacts and significantly smaller. At best, I believe that jpegmini is only using some smoothing.

To reach this conclusion, I used the following quantization table optimizer: http://pages.cs.wisc.edu/~ratnakar/rdopt.tar.gz

Which is described on this paper: Extending RD-OPT with Global Thresholding for JPEG Optimization

Curiously, the authors of the two papers I mentioned before have published another one where they get a 40-45% file size reduction by using optimization of quantization tables + run-length encoding + arithmetic encoding:

http://ieeexplore.ieee.org/ielx5/5075165/5090078/05090215.pdf?arnumber=5090215

Given that the respective patents are 8 and 6 years old:

• http://www.google.com/patents?id=rKrRAAA...&q&f=false
• http://www.google.com/patents?id=7JKaAAA...&q&f=false
  

I start to wonder if the aforementioned research, funded by public money, will ever be translated on a JPEG compressor for sale on the market using those algorithms.

[Aaron Kulick]

Of the open source tools, I am still a big fan of jpegoptim and jpegtran.

Aaron

[jarrod1937]

Sorry if i am hijacking this thread, but it's a very closely related question. But what is the best image resizing and compressing library that has been exposed via php? Currently we're using imagick, any better ones out there?

p.s. Yes i know you can make calls to any on system executable via php, but i have that ability disabled for security sake, so it has to be exposed through php.