PNG File Format
SUMMARY: A beginner's guide to the PNG image file format, often used as an alternative to lossy-compressed .JPG images
The .PNG file extension refers to images formatted as PNGs (Portable Network Graphics). This format allows for images to be stored in a compressed manner so they take up less space than, for example, .BMP graphics.
However, unlike "lossy" compressed formats such as JPEGs, PNG images are lossless compressed, meaning that no information/image quality is lost between a source image and the resulting PNG. This usually results in a larger file than if the image was saved as a JPEG. However, since JPEGs are recompressed on each save, re-editing and re-saving JPEGs will introduce more artifacts in the image; this does not happen in a lossless format such as PNG.
PNG images may support a subset of colors, such as .GIF images, or they can represent up to true-color photographs. Other features supported including transparency, allowing one to place a PNG image over another image so that parts of the lower image are seen. Plus, PNGs may support partial transparency, allowing for more realistic effects when placing one image over another.
PNG images are becoming more and more frequently-used on web sites. However, older versions of browsers, especially Internet Explorer where version 6 is still being used, may have difficulty displaying such images. Or, they may not handle certain PNG features such as transparency and gamma correction.
Virtually any modern image / photo editor supports reading and writing .PNG images, though they may also not support every feature including alpha / partial transparency.
Windows users: NOTE that unless you have configured your computer with the file extension viewing tweak (Windows Vista instructions for the file extension viewing tweak) (Windows 7 instructions for the file extension viewing tweak), it is possible that a filename that looks like it ends with ".png", especially one attached to an e-mail message, actually has a hidden OTHER extension, meaning that if you double-click the file, it may actually run a computer virus!
Return to the File Extensions page.
blog comments powered by Disqus