Tag Archives: glossy

Google’s Guetzli vs. ShortPixel’s Glossy algorithm

Guetzli vs ShortPixel

Guetzli is the new JPEG encoder developed and released as open source by Google. It is designed to produce ~35% smaller files, without compromising  the picture quality. We, at ShortPixel, had recently our own update: ShortPixel Glossy optimization, the lossy new algorithm for photographers.

Testing Guetzli algorithm was mandatory for us. When you are in the image compression business, you need to get your hands on any brand new innovation and see what it can do.

How does Guetzli compare with ShortPixel’s new Glossy image optimization algorithm in terms of quality and performance? Can we use it alongside our algorithms? Does it have practical value for our users?


Testing conditions

Guetzli was tested on a quad-core Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz processor. We used Guetzli setup with two parameters: 84 and 95. 84 is the minimum quality allowed by Guetzli, and 95 is the default setting (in this case, a bigger number means better quality and larger files).

As we mentioned before, Glossy is our new image optimization algorithm for photographers. The images optimized this way look brilliant  while being considerably smaller than their Lossless version.  Glossy optimization algorithm runs on ShortPixel cloud servers, where your images are also optimized.

The images compressed in this test are from the amazing Unsplash website. You can find all files, both originals and processed, in the attached archive. At the end of this article, you can also see the complete image credits list.


Guetzli VS ShortPixel: test results

Image size improvement, compression speed and picture quality – these are the most important factors we gathered for this comparison.

File size improvement
ShortPixel Glossy produces smaller images than Guetzli at 95 setting for all tested images, and it has an overall improvement comparable with Guetzli 84.

 OriginalGuetzli 95Guetzli 84ShortPixel Glossy
Img-15 MB1.7 MB1.1 MB804.6 MB
Img-29.3 MB2.5 MB1.2 MB1.5 MB
Img-31.4 MB485.1 kB250.7 kB97.1 kB
Img-45.6 MB1.5 MB778 kB1.4 MB
Img-535.5 MB10 MB6.1 MB6.5 MB

Optimization speed
Speed performance is Guetzli’s weakest point. Google encoder needs several minutes to process the images, while ShortPixel takes seconds to optimize the same files.

 Guetzli-95Guetzli-84ShortPixel (Glossy)
Img-19m 01s9m 40s 8.7s
Img-29m 29s6m 30s 6.5s
Img-37m 56s4m 53s 3.2s
Img-47m 02s7m 45 6.4s
Img-531m 33s25m 47 26.8s

Picture Quality
Our users are not scientists, they don’t use image analyzing software, they simply look at images and decide for themselves if they look good or not.

Look at these 100% cropped images and see the differences between Guetzli processed files and the images optimized with ShortPixel Glossy. Remember that WordPress has its own compressing settings and the best way to compare the images optimized with different algorithms is by looking at the full sized pictures found in the attached archive.

Image comparison


image 2 - guetzli glossy optimization comparison



Please click here to download the archive containing the full sized images.


Google has a lot of talent resources, and it is not surprising that their algorithms are smart. Guetzli produces good results.

Picture quality is really good when the encoder is setup at 95, but files are pretty big. Changing the option to 84 brings a decrease of picture quality as you could see in the above examples.

Images optimized with ShortPixel Glossy algorithm have a picture quality close to Guetzli-95, but with a pretty good quality-compression ratio. Remember that we recommend ShortPixel Lossy optimization if you want Google PagesSpeed Insights improved results.

The biggest issue of Guetzli in our opinion is the incredible amount of time it takes to deliver the results. You need a computer with a lot of power to run it, and it is very slow. Developers could tweak its parameters, but we are not sure if Guetzli is a practical solution for regular users.

We are not so happy with this conclusion, because we considered useing Guetzli alongside our algorithms. Currently that is not feasible: it takes too much time and processing power to deliver results that are comparable (if not worse) that those delivered by ShortPixel’s Glossy.

Get your image optimization tool of choice!
Finally, you are the jury, and you decide which tool is the best choice for you.

Get ShortPixel from WordPress.org
(or install it directly from your WordPress dashboard, search for “shortpixel”).
Download Guetzli from the Google GitHub page.

Image Credits

Img-1: andrew-phillips-22066.jpg
Source: Andrew Phillips

Img-2: cloudvisual-208962.jpg
Source: CloudVisual

Img-3: miguel-mateo-212333.jpg
Source: Miguel Mateo

Img-4:  mitchell-hollander-205952.jpg
Source: Mitchell Hollander

Img-5: robert-zunikoff-53898.jpg
Source: Robert Zunikoff

Glossy, image optimization option for photographers

Glossy - optimization for photographers
Image source: Cameron Kirby

ShortPixel introduces a new image optimization option called Glossy. The new feature is a lossy optimization algorithm calibrated for the photographer’s needs. We still recommend Lossy for the most user cases, because it has the best balance between image optimization and picture quality.

Why we built Glossy?

We added the new optimization option because some professional photographers asked for it. For them,  image quality comes first,  before page speed .

Photographers are able to see details in images which most of us might miss. Many of these users always preferred lossless optimization to lossy.  But, web standards, mobile popularity and visitors expectations changed in the last years, and lossless optimized images became too big for the present market standards.

The images optimized with Glossy look identical to the human eye with the original images, but they comply with the present criteria regarding the web applications.


Lossy, Glossy or Lossless – which one is the best for me?

Lossy is the best option for the most users. The images processed with Lossy algorithms are the smallest optimized images you can get. So, if the speed of your site is paramount and you want the best balance between optimization and picture quality, we recommend you to continue to use Lossy optimization.

Glossy is the best choice if you still care about Google Insights but you believe that a slight loss of page speed is an acceptable compromise for a top notch image quality.

Lossless optimized images are pixel-by-pixel identical with the originals, but they offer a smaller size reduction compared to either Lossy or Glossy processed files. If you want your images remain untouched, then select this option.


Lossy, Glossy, Lossless – a comparison

The best way to choose the proper optimization for your images is to see how they look with your own eyes. Here is an example, but you could make your own tests using your own images.

Original image

Original image

Please compare the cropped images or click on them to open the full versions, and see how they suit your needs.

Original (cropped)

Original Image cropped.
Original image cropped. Full sized image has 2.32 MB.

Lossless (cropped)

Lossless image cropped
Lossless image cropped. Full sized image has 2.30 MB.

Glossy (cropped)

Glossy image cropped.
Glossy image cropped. Full sized image has 514,4 kB.

Lossy (cropped)

Lossy image cropped.
Lossy image cropped. Full sized image has 407,9 kB.

How to glossy-optimize your images?

Go to ShortPixel settings panel, General tab, and change the optimization method to Glossy:

How to choose Glossy image optimization.
How to choose image optimization type.

After you set your image optimization method, you could either process images one by one from the Media Library or you could go the ShortPixel Bulk page and re-optimize all your images.


Glossy integration, next steps.

We spent a lot of time tweaking the algorithms for Glossy, and we are confident that it will cover most of the photographers needs. Give it a try and install it from WordPress.org!

Next steps are to add the Glossy optimization to our online image compressor and to make the new feature known to the photography community.

We really need your help to grow! Let your friends know about ShortPixel WordPress plugin and the friendly team that built it 🙂