Realmac, the developer behind web design software RapidWeaver, has just launched Squash, an image-compression app for Mac. Normally $20, the company is making it available for a special launch price of just $8 between now and Monday.

While image-compression isn’t exactly the most exciting of fields, it can be very handy to be able to compress photos to more manageable sizes to email to family and friends or to use on the web. You can drag single images, multiple photos and entire folders onto the app, and choose between overwriting the originals or – by default – appending a suffix to the compressed versions …

I’ve been testing Squash, and it does an extremely impressive job, both in terms of ease of use and end result. Not only does it appear to meet its promise of reducing filesizes without visible loss of quality, but you can also feed in RAW, TIFF and PSD images as well as JPGs.

You can tweak the image-compression in the settings, but I honestly haven’t found any need to – and I’m very fussy about photo quality.

In my tests, the detail looked just as good in the compressed images as in the original. There are no visible compression artefacts. I do see some tiny colour differences, perhaps from simplifying the colour data, but I really had to pixel-peep to see this. Sharpening is applied, but this is very subtle.

Below you can see an example of a photo I compressed using Squash. Here’s the photo as a whole:

citypoint-london-skyline-3

The full-size image is 4256×2832 pixels, and the original was 7.5Mb. After compression by Squash, the resolution remains unchanged, but the compressed version is 2.3Mb – or less than a third of the original size.

Here’s a 100% crop of a small part of the original, unsharpened image:

orig-100

And here’s the compressed version:

You can see Squash in action in the video below, and buy it from the Mac App Store .

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