PNGs - worth using?

[Spunkey]

Hi all,

I'm just in the middle of creating a site, and because of the background i have to use (feckless orders from on high) i'm looking to use transparency for a few graphics.

Its not often i use transparency as i hate GIFs with a passion, so PNGs seem the only alternative.

I've written the page so that it detects the browser and does all the shenanegans needed to display TGAs properly in all browsers. I'm just wondering if there is any other reason I've missed why TGAs aren't widely used.

I've googled but i cant find anything obvious.

TIA

[Stoo]

mainly because of all the messing about you have to do to get them to display in all browsers..

/me shoots Microsoft..

..and if you're using larger images JPEG's are smaller, and if you're using small images gif's are smaller..

[Zathras]

You can usually get PNGs smaller than GIFs, and if not the difference is of the order of 5% maximum. It's just people usually don't know how to make their PNGs correctly. Have a look at http://libpng.org/pub/png/pngfaq.html

IE has pathetic alpha-channel rendering. IE will display PNGs with simple transparency (gif style transparency) absolutely fine but messes up with anything more complicated - see http://www.youmustbejoking.demon.co.uk/pngtest/test/ and http://www.youmustbejoking.demon.co....est/tests.html for how they should be displayed. http://webfx.eae.net/dhtml/pngbehavior/pngbehavior.html has a hack to fix this in IE.

[yamangman]

GIF's aren't so bad. If you have an image with few colours use GIF, you won't get the noticeable compression noise that you get with a JPG, talking comparative sizes of course.

[TomWilko]

What is the advantage of this PNG lark over the old-school JPG's and GIF's?

[Zathras]

PNGs are lossless like GIFs, so you won't get any compression effects unlike JPEGs. PNGs and GIFs are typically used for icons, small images or images with continuous blocks of colour, whereas JPEGs are used for larger images and photos where a bit of alteration of the image won't be noticable.

Unlike GIFs, PNGs support more than 256 colours, and also have an alpha channel meaning the images can contain varying degrees of transparency. This lets the images seem smooth when set on a patterned background, something not possible with either JPGs or GIFs. GIFs also contain patented compression code and Compuserve IIRC have to be paid a license fee by software manufacturers when they make GIF-producing software, whereas PNG is an open Free standard.

[directhex]

(unisys lzw patent)

[Zathras]

Unisys own the patent, Compuserve get paid the royalty AFAICS as they 'own' the GIF format.

http://lpf.ai.mit.edu/Patents/Gif/origCompuServe.html

Interestingly the patent was set to expire last year. Not sure what's the current situation with it, but PNGs own GIFs, even after taking into account IE's broken rendering.

[directhex]

hmm, no, have to say, much as i love PNG, if you WANT visitors running spyware explorer 6, then PNG is more trouble than it's worth

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spyware explorer 6 classic but true