The ubiquitous Zip file compression format has been a staple of PC users since it first made its debut as PKZIP in the early 90s. Back then, the size limitations of floppy disk media and the painfully low-bandwidth dial-up connections made file compression a complete necessity. The Zip format today, while still popular, has largely been eclipsed by RAR compression, which has offered slightly better compression at the cost of archiving speed. That’s why we were so surprised to hear that WinZip 12, which launched yesterday, boasted an unbelievable 25% compression ratio for JPEG images – without sacrificing image quality. Ever the skeptics, we put the new software to the test, and grilled WinZip’s VP of Development about how this new algorithm works.

We decided to test WinZip 12 on a large folder of high-resolution JPEG photos, each ranging from three to four MB, and totaling 1.13GB (or 1,217,671,445 bytes). This photo gallery (taken at this year’s PAX), was made up of 301 photos, each at 3888x2592 resolution, and taken straight from our Canon 40D camera.

Dragging the files into the WinZip program window, we were shown a pop-up with typical configuration settings, including the target destination and encryption options. The one notable difference was the presence of a “Change Compression” button. This opened a new window with two distinct compression options: “Legacy Compression” and “Best method for each file type”. We decided to give both a try.

With Legacy Compression, our newly compressed file ended up as 1.13GB, or 1,214,464,603 bytes. The total space savings displayed was 3.10Mb over 300 images, or about 1%. Looking at each individual file in the archive, we saw an average of 10KB reduction for each photo. Not particularly impressive, though at least the zipped file wasn’t larger than the original folder (which we’ve seen occur with poor compression algorithms).

“Best Method Compression” faired much better. Changing the compression setting to the new optimized algorithm churned out a 927MB file (972,699,916 bytes), or an approximate 20% size reduction. Color us surprised. We unpacked the new Zip file to examine the JPEGs and couldn’t find any difference between those and the originals – no new compression artifacts.

But here’s the catch (and there always is one). Compressing with the new algorithm took almost four times as long on a dual-core Pentium D machine than with Legacy Compression. Also, the new Zip file was only compatible with WinZip 12 – it wouldn’t open with Windows XP or Vista’s native archive browser, let alone on OS X’s built-in Zip app. That means that these files are useless unless you pay for WinZip 12. We contacted WinZip to find out exactly how the algorithm works, and how they expect to get the internet community adopt it.

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Software, interview, JPEG, archive, features, zip, compression, winzip, winzip 12

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