At Last, PNG An ISO Standard Under Publication

Jeex writes "After its first draft back in '95, the Portable Network Graphics (PNG) format is finally, as of 2003-04-25, an ISO standard under publication. Links: ISO technical programme: JTC 1/SC 24, PNG Homepage."

Comments

Re:GIF and JPEG . . .

[fredrikj]

PNG is lossless by definition. (GIF is also lossless, although only when the source image has 256 or less colors.)

The definition of lossless is that if you take an uncompressed bitmap, compress it with the compression method, and then decompress it, you'll get a file that is identical to the source bitmap, bit by bit. PNG is based on a general-purpose compression method, IIRC the same one that's used in .zip files, so you can (!) use PNG to compress executable files or audio files or whatever, if you just feed them into the encoder as raw images. PNG packs by patterns in the byte structure, and no data is lost.

This is not the case for JPEG. JPEG doesn't compress by the data bits, but reformats the image as an approximation of the source image, based on the redundancy of color values as they appear in the rendered image. A JPEG image cannot be decompressed to an image identical to the source it was generated from. Therefore, JPEG is lossy.

Re:GIF and JPEG . . .

[Webmonger]

GIF and PNG use lossless compression techniques. They are lossless. If you have a black-and-white image and you save it into GIF or PNG, you will get an identical image back when you load it.

You're confusing format with interface (because you refer to options used, and those are an interface thing). GIF is lossless, but it can only represent images with 256 colours or less. (Black-and-white images meet that test.) It's impossible to save an image with more than 256 colours as a GIF, so many programs will convert it for you. That doesn't mean GIF is lossy. Just means that it has limitations. Save any 256-colour image, load it up, and you'll get exactly what you had before.

IE cannot read MNG

[yerricde]

a flimsy one at best as MNG is "PNG+animation", in the same way GIF89a is "GIF87+animation".

There's a big difference: Out of the box, the most recent released version of Microsoft Internet Explorer can display GIF89a animations. Out of the box, the most recent released version of Microsoft Internet Explorer cannot display MNG animations.