APNG comes as a modification of the well-known PNG format, but with additional support for animation. It supports 24-bit images and 8-bit transparency, having a much better quality then the classic GIF format.
An APNG file contains ordinary PNG frames, with two additional data chunks: aDAT (animation data chunks) and fCTL(the frame control chunk). Any PNG decoder should be able to decode the first frame of the APNG file as an ordinary PNG image. Any APNG data file must be subjected to certain rules:
The size of the entire APNG
"APNG is designed to allow incremental display of frames before the entire image has been read. This implies that some errors may not be detected until partway through the animation. It is strongly recommended that when any error is encountered decoders should discard all subsequent frames, stop the animation, and revert to displaying the default image. A decoder which detects an error before the animation has started should display the default image. An error message may be displayed to the user if appropriate.
Structure
An APNG stream is a normal
"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
This page is intended to provide an explanation of some of the features of the PNG format for non-technical users. As such, it doesn't emphasize PNG features like freedom from patents; those are more of concern to developers. Where programmer information is given, it is principally to explain to the user why various applications may not perform as well as expected. Where performance claims are made--especially compression comparisons with other image formats--we assume that the PNG implementation is at least as good as the best freeware encoders. Note
This page is intended to provide an explanation of some of the features of the PNG format for non-technical users. As such, it doesn't emphasize PNG features like freedom from patents; those are more of concern to developers. Where programmer information is given, it is principally to explain to the user why various applications may not perform as well as expected. Where performance claims are made--especially compression comparisons with other image formats--we assume that the PNG implementation is at least as good as the best freeware encoders. Note
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
This page is an attempt to provide an easily digested PNG status board--basically a place to come and see how PNG currently fares for those who haven't been keeping up with the news page or mailing lists. It grew out of an article submitted to Slashdot in February 1999 (with a followup in June 2000), but it is intended to be more dynamic and has been redesigned accordingly.
Stability: excellent * * * * *
The PNG specification has proven to be exceptionally solid. There have been two minor updates since the 1.0 release--to clarify gamma handling and to
Status of this Document
This is a revision of the PNG 1.0 specification, which has been published as RFC-2083 and as a W3C Recommendation. The revision has been released by the PNG Development Group but has not been approved by any standards body.
The PNG specification is on a standards track under the purview of ISO/IEC JTC 1 SC 24 and is expected to be released eventually as ISO/IEC International Standard 15948. It is the intent of the standards bodies to maintain backward compatibility with this specification. Implementors should periodically
# Introduction
The png-16 image format stores imagery in 16-bit pixels. It is being developed to offer several unique benefits:
* losslessly compressed true-color imagery in smaller files then 24-bit color
* provide a display space for color imagery indistinguishable from 24-bit color
* provide an analytical and display space for grey imagery up to 12 bits per pixel
* allow deep grey and true color to co-exist in less than 48 bits per pixel
* add extra image features such as:
o positive and negative transparency
o extremely flexible color
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