PNG is a file format used especially for images. It is a free file format, meaning that it can be used by everyone in any way he wants it without paying any royalties to anyone. But this is not the main advantage of PNG, I would even call it a minor advantage, as the end-users do not quite feel it.
The PNG format was intended to be a replacement for the older PNG format and, in some ways, to the TIFF format. It's mainly used in two areas: World Wide Web and image-editing.
On the Web, PNG is much better that GIF. It has included
This material is intended to inform the simple users about the features of the PNG format. So, it will pass over some details like for example the freedom from patents, as this has no connection to the end-user, being more of a concern for the developers.
The PNG format was intended to be used like a substitute for the GIF and TIFF formats. So, it was created with two main ways of usage in view:
World Wide Web
Image editing
PNG can be widely used for the web, having several advantages over the GIF format: the possibility of
"For the Web, PNG really has three main advantages over GIF: alpha channels (variable transparency), gamma correction (cross-platform control of image brightness), and two-dimensional interlacing (a method of progressive display). PNG also compresses better than GIF in almost every case, but the difference is generally only around 5% to 25%, not a large enough factor to encourage folks to switch on that basis alone. One GIF feature that PNG does not try to reproduce is multiple-image support, especially animations; PNG was and is intended to be a
APNG is an extension of the PNG format, adding support for animated images. It is intended to be a replacement for simple animated images that have traditionally used the GIF format, while adding support for 24-bit images and 8-bit transparency. APNG is a simpler alternative to MNG, providing a spec suitable for the most common usage of animated images on the Internet.APNG is backwards-compatible with PNG; any PNG decoder should be able to decode the first frame of an APNG and treat it as a normal single-frame PNG.
PNG Structure
An APNG stream is a
For those of you who simply wish to buy a commercial application or download a zipfile full of executables and start looking at or making pictures, the pages below have pointers to a large number of applications that are known to support PNG in one form or other, or that are going to support PNG in the near future. Some of the programs (particularly those for Unix) are provided as source code and may require libpng and/or zlib (see PNG Source Code and Libraries), but often even these have pre-built binaries for popular systems somewhere nearby.
Also
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