- From: Anthony Grasso <anthony.grasso@cisra.canon.com.au>
- Date: Mon, 20 Sep 2010 09:10:24 +1000
- To: David Woolley <forums@david-woolley.me.uk>
- CC: ddailey <ddailey@zoominternet.net>, www-svg@w3.org
On 20/09/2010 4:22 AM, David Woolley wrote: > ddailey wrote: > >> 1. The spec says "Conforming SVG viewers need to support at least PNG, JPEG >> and SVG format files." Why not GIF? I recall a profound nervousness > > I think the basic reason is that PNG can exactly represent any image that GIF > can represent, except for animations, and usually does so more compactly for > equal quality, but also has the option of better quality. > In saying that, there is nothing stopping an SVG viewer/editor (to my knowledge) from supporting GIF in addition to JPEG and PNG. :) >> that spread like squid ink through the open source community [1] 10 or 12 >> years ago as the holders of the GIF patent threatened to go after those who >> used it without license. I believe, however, that the patent has since >> expired. [2] A search of gif in Google images shows about a billion files with >> close to half that number for PNG. In many cases GIF > > Image formats are often chosen without any real understanding. There are an > awful lot JPEG images (or PDF images using DCT) that are totally unsuitable for > JPEG, either because people believe it produces the best compression for > everything (and only make one dimensional decisions), or because they don't know > PNG and paintbrush produces very poor GIFs. > >> files are smaller than PNG files, I think, and lots of the older public > > Although it is possible, and may be more common for very small images, the > compression scheme used in PNG is generally better than that used in GIF (the > LZW used in GIF, and the actual subject of the patent, is designed as a > compromise between compression speed and and compression ratio - it was really > intended for real time compression of streamed data. That in PNG is designed to > give good compression, at the expense of slow compression speeds. > > Apart from the possibility that PNG may have a higher overhead, the other reason > that you may observe this is that PNG has more possible formats, and, for > example, paintbrush uses 24 bit unpalletised for PNG and uses a non-optimised > palette for GIF. > >> domain imagery sites on the web used gif because, well, PNG wasn't available >> then. All the browsers I know of go ahead and support GIF anyhow, but it is >> one thing we can be certain of that no longer has patent entanglements. PNG?? >> Who can ever be completely sure until the 20 years pass? >> > It's very likely that any such patent would also affect GIF. >
Received on Sunday, 19 September 2010 23:10:59 UTC