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An Investigation
into the PNG Format

April 6, 1998

This article is not intended for the techies. It is aimed at the non-techies like myself who would like to know the basics of PNG, why it may be a useful alternative to other standard formats and will highlight only the issues and features of immediate interest. First, what is PNG? It's an image format designed to replace the standard GIF format (pronounced with a soft G like giraffe). PNG is an acronym for Portable Network Graphics. PNG is pronounced "ping," not "ping" or "pee en gee." This new format has two major uses: The World Wide Web and image-editing. It's compression engine can compress better or faster. PNG requires NO patent fees.

World Wide Web Use
In almost every case, PNG compresses better than GIF at around 10% to 30% difference. This isn't enough to warrant switching to PNG, but variable transparency, cross-platform control of image brightness, and two-dimensional interlacing WOULD be reason enough to change over from GIF to PNG. Unlike JPEG, PNG does not lose anything in compression and supports up to 48-bit truecolor or 16-bit grayscale in saving, restoring and re-saving PNG formats does not result in quality loss. However, JPEG losses can be minimized and the file size savings even at high quality levels is still better than a lossless PNG.

Image Editing
Comparing JPEG, GIF and PNG for supporting image types: PNG supports images in truecolor, grayscale and palette. JPEG supports only truecolor and grayscale and GIF supports only palette. By using the gray palette, GIF can imitate grayscale. Then there are the advantages of alpha channels, gamma correction, and file integrity checks which are too technical for this simple review of PNG. Detailed Information can be found using this hyperlink.

Advantages of PNG Images

Can have trillions of colors in a single image
10-30% smaller file size than GIF files
Many levels of transparency - GIFs can have only one
Can contain searchable information about content, history, and authorship
Can be combined with JavaScript and HTML Layers and dynamically tinting images
Royalty-free format for the Web
Sizes can use WIDTH=X% and HEIGHT=Y% to scale images automatically to fit the browser window.
Netscape Communicator users can download a plug-in created by Siegel & Gale to allow them to view Web sites with PNG images

Tools to Convert Existing Images to PNG
Most of the graphics programs we already use will convert images to PNG. SmartSaver by Ulead is my choice. It can be used as a stand-alone program or if you already own PhotoImpact 3.x, SmartSaver is a simple upgrade and will plug in to PhotoImpact. There's also a trial version you can download. Ulead's WebRazor includes SmartSaver as part of the package. The newest version of SmartSaver has three options for exporting, compressing and saving images. This image is the three selections available from the Export screen:

Now What?
Though PNG is not yet a standard replacement for GIF, JPEG, or TIFF, the advantages are obvious for any webmaster or programmer. It would be fun to at least set up one page on a set of Web pages for testing everything from loading time to the enhanced colors and providing surfers with a place to test their plug-ins for Netscape Communicator. Two good resources available:

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An Investigation into the PNG Format

An Investigation
into the PNG Format