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They call it MrSID, but it’s not a character from an old TV show; the name stands for Multi-resolution Seamless Image Database, an image-compression technology from LizardTech. The first Mac implementation is MrSID Publishing Edition, primarily for pre-press applications, which offers higher-quality image compression than the reigning JPEG standard.
MrSID uses wavelet scalar quantization compression, an improvement on JPEG’s discrete cosine-transform technology. Both are lossy compression schemes – meaning that they sacrifice image data as the compression ratio increases. However, MrSID can compress pictures at higher ratios than JPEG, without adding the artefacts often found in highly compressed JPEG images.
At the program’s core, is an Adobe Photoshop plug-in, accessed through Photoshop’s Save As menu option. You choose a compression ratio by entering a number, moving a slider, or specifying a target file-size.
To see how MrSID compares with JPEG, we compressed a series of images, at various ratios, using both technologies. We also compressed the images using Altamira Group’s Genuine Fractals Print Pro, which offers a compression ratio of about 5:1.
The differences between JPEG and MrSID are dramatic. At a 30:1 ratio – enough to squeeze a 12MB image down to 400K – the MrSID image displayed only minor artefacts. The smallest JPEG file – about 20:1 – showed extensive artefacts, even though it was larger than the MrSID image. At a 10:1-compression ratio – equivalent to JPEG’s medium compression – MrSID really hit the sweet spot, exhibiting no discernible artefacts at all. Indeed, picture quality was comparable to that of the Genuine Fractals image, which was about twice as big. However, unlike Genuine Fractals, MrSID does not let you scale an image up beyond its original size.
The MrSID package includes a Photoshop plug-in for distribution to users who need to view your images, plus a browser plug-in for viewing images online. A Quark XTension lets you import MrSID images into QuarkXPress, where you can view and print them. All three modules are available as free downloads from the company’s Web site.
At £299, MrSID is pricey. However, it offers much better image-quality and higher compression-ratios than JPEG. If you frequently transmit high-resolution images, and you don’t want to compromise on quality, give this package a look.