The PNG Guide is an eBook based on Greg Roelofs' book, originally published by O'Reilly.

Image Viewers

Unlike, say, image converters or editors, there is generally not a great deal to say about a PNG-supporting image viewer other than that it does, in fact, display PNG images. Gamma correction is the primary ``special'' feature one would like; color correction and the ability to view text annotations would be nice as well, but the reality is that most image viewers concentrate more on speed and breadth of support for different image formats and display depths than on features specific to any one format.

The list of viewers presented here is likewise long on breadth and short on specifics, simply because testing every viewer for every platform--or even a reasonable fraction of them--is impractical. Gamma and text support are noted wherever known, as is the ability to convert to or from other formats, but this is primarily a laundry list of viewers, sorted by platform. The current version of each, as of this writing, is listed wherever possible.

It is even less practical to test every one in 2003 than it was in 1999; the PNG web site now lists more than 90 additional viewers that either did not support or were not known to support PNG when the first edition went to press:

The web page is updated regularly, but even so, it is guaranteed to be incomplete; PNG support is no longer remarkable, and new viewers are released all the time, usually without any mention of specific image formats. These days almost every image viewer (with the exception of some--but not all--viewers for embedded devices) can be assumed to support PNG.

In addition to the viewing applications listed in the following discussion, two demo viewers are described in Chapter 13, "Reading PNG Images", and Chapter 14, "Reading PNG Images Progressively". They currently run under 32-bit Windows and Unix/X, and full source code is freely available. One other viewing application is also worth mentioning: Aladdin's Ghostscript, currently at version 5.50, which is (or has in the past been) available for every platform listed here. Ghostscript is a viewer for PostScript and Acrobat (PDF) files, but it can write PNG images and is therefore a special case.

Last Update: 2010-Nov-26