Enterprise Software

True image formats

Picking the right true image format depends on various factors. Find out how to decide which format is best for you.

By Paul Anderson

A true image format accurately stores an image for future editing. There are dozens—if not hundreds—of existing true image formats, and picking the right one depends on which editing tools you plan on using, as well as whether you need to share the files with others who might use a different set of tools.

Every major computer operating system has its own native image format. Applications written for a given operating system are almost guaranteed to support that format, so you can play it safe if someone needs the image and you know the platform the person uses. Windows and OS/2 use the BMP format, while Macintosh prefers the PICT format. Unix desktops based on X Windows, such as GNOME, favor XWD files. All of these formats support full 24-bit color but can also compress images with sufficiently few colors into 8-bit, 4-bit, or even 1-bit indexed color images.

Tagged Information File Format (TIFF) is a loss-free, 24-bit color format intended for cross-platform use, and it tends to be accepted by most image editors on most systems. The only drawback is that TIFF has evolved into several incompatible versions, so different image editors may not be able to read each other's TIFF files. But recent versions of popular applications such as Photoshop and CorelDraw should have no problem.

By far the most promising loss-free format is the Portable Network Graphic (PNG). It accurately compresses 24- or even 32-bit color images, the latter of which are 24-bit images with an added 8-bit alpha, or transparency, channel. It also indexes images with 256 or fewer colors for further compression and supports gamma correction. Best of all, it's intended to be a Web format. Most recent graphics applications can read or create PNGs, and modern browsers support the format, albeit inconsistently.

Paul Anderson is associate technical editor for CNET Builder.com. His responsibilities don't include handling graphics, so naturally, he handles them all the time.

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