What Is The Future of PNG?

miladus writes "The GIF patent (held by Unisys) will expire on June 20. C|Net wonders whether that will also mean that PNG "will lose its original reason for being". Remember Burn All GIFs? " My hope would be that at this point PNG can stand on its own technical merits, rather then on ideological merits.

PNGs

Unfortunately even half my coworkers don't know what a PNG is. I try to send them a UML diagram made from DIA and they demand a readable format :(

Re:PNGs

Out of interest, what the hell sort of software are your idiot coworkers using if they can't load a simple PNG? I can't understand this; every time someone mentions PNG, people always complain that they nobody has heard of it and no application can handle it. What? I use PNG for everything I do. I've never had a problem saving or loading it, unless for some bizare reason I'm using ancient Windows applications that can only handle BMP, TIFF and PCX of all things. I really don't get it!

Re:PNGs

Reasonably modern?! If I recall correctly, IE4 already has PNG support (minus alpha transparency). IE3 won't fit in the "reasonably modern" category anytime soon.

Re:PNGs

Yeah, and IE6 has the exact same support. PNG, no alpha transparency. The single most-used browser in the world is the only one lacking the most attractive feature of PNG files. Even IE5 on the MAC has alpha support.

If PNG fails, I think that the blame for that falls squarely in Microsoft's lap.

Re:PNGs

Yeah, and IE6 has the exact same support. PNG, no alpha transparency. The single most-used browser in the world is the only one lacking the most attractive feature of PNG files.

Since there seems to be a lot of coding pages for IE anyway, one can help IE out [mongus.net] where they can't (or won't) do it themselves.

not yet...

until GIF gives us more than Alpha channel with more than 1 bit :)...

ought to be enough

One bit, that ought to be enough for anybody... :-)

Re:not yet...

That's only sort of correct. A gif can ONLY do transparency. A PNG allows up to 254 levels of partial transparency per channel, and can have multiple channels.

You want to know what REALLY held PNG back? It was Internet Explorer that STILL doesn't do the transparency right. More eople would start using the format right now if the implementation could do what the spec specifies. You see people all the time finding clever ways to make an image look like it blends into the background - which can be a pain in the ass to line up correctly. Imagine if the images could actually do partial transparency... that would make things easier woudn't it? Oh well, it's still a good lossless algorithm to cart images around with - I use it all the time for personal use and on my website.

Re:not yet...

IE 6, at least on NT-based systems, even screws up the palettes on PNGs.

I can save a graphic using RGB 102,0,0 and I would have to change it to RGB 115,0,0 or something similar to match the background color attribute of the HTML page.

IE is horrendous on PNG graphics, still to this day.

Two solutions for IE 6 PNG color mismatch

What you're seeing is probably gamma correction. Try saving the PNG image without a gamma chunk (GIMP's Save As... dialog can do this), and your image's #660000 will match your page's #660000.

If it's not gamma, then it's probably differences in dithering. In high-color mode, some web browsers use different dithering algorithms on flat rectangles (e.g. backgrounds) vs. images. If this is your problem, the problem should show up with GIF images as well. Here, the best policy is to use a binary-transparent PNG, masking out what touches the edges and matches the background. (IE supports binary transparency in indexed images, just not alpha.)

here's hoping.

I am dying for full PNG support in all major browsers... the 256 levels of transparency alone make it worth while!

Re:here's hoping.

Same here, and it's pretty close. Most browsers support it in some fashion, and it IS technically superior to GIF format images.

It's a little like MP3 vs OGG, except PNG is far closer to acceptance in general applications than OGG is for music.

Curiously, does IE support more than one alpha channel with PNG? last I looked it didn't, but that was a long long time ago; most everything else did at the time

Re:here's hoping.

I was wondering about this just two or three weeks ago, and tested with Mozilla and IE 6. Both of them can display PNG files, but it's only Mozilla that could render the 256-level alpha channel properly. Made for some very neat effects. IE didn't manage the transparency at all. :-(

Re:here's hoping.

I was wondering about this just two or three weeks ago, and tested with Mozilla and IE 6. Both of them can display PNG files, but it's only Mozilla that could render the 256-level alpha channel properly. Made for some very neat effects. IE didn't manage the transparency at all. :-(

You can easily test your browser here [entropymine.com].

Re:here's hoping.

Results on the browsers I have handy (without reboot)

Opera 7.11 -- perfect
Mozilla 1.3.1 -- perfect
Netscape 7.02 -- perfect
IE6 SP1 -- totally broken

No surprises here.

Re:here's hoping.

This is such a sore point for me. To me the main raison d'etre for PNG's is that alpha transparency instead of the single-bit transparency that GIF's offer.

However, IE for Windows supports it *horribly*. If you want to use the alpha transparency feature of PNG's, you've got to jump through a lot of crappy, nonsensical IE-only hoops.

Here is a rather funny page [homelinux.net] (since the author's disbelief and anger at IE's horrible behavior is palpable) which does a good job of explaining the issue, and supplying a few workarounds.

It's a shame that IE is so crappy in this regard (and plenty of others, but that's another discussion)... there's no good reason for it. Apparently IE for Mac supports them just fine, btw... so it's not like Microsoft has some official PNG-hating policy, they just simply got sloppy with IE/Win. Another good example why too much share in a given market (in this case, web browsers for Windows) is a bad thing for competition. Why should they bother improving or fixing IE/Win? What's in it for them?

PNG is an in-use MS Office format

PNG is used as part of MS Office Documents for their binary picture data, so one suspects that making it work in IE will make more things break elsewhere.

Sure

Because everyone wants 256 color GIFs.

PNG does everything GIF does, only a million times better.

Except, of course...

MNG files, which are animated PNGs.

Re:Except, of course...

I don't know about other browsers, but MNG support has been dropped from Mozilla in recent builds. Apparently the MNG library was quite large (apparently just a few hundred k, though...), and rarely-used, so it was dropped as part of a bloat-reduction effort. Can't say I agree with them. More discussion can be found over at the mozillazine.org forums.

Re:Except, of course...

Much as I feel the same, I don't think that's quite true. Surely there are some cases where it's appropriate to use a light-weight animation and something like .mpg would be overkill.

Agreed. Animated GIFs can be very useful - it's just that 99% of sites seem to use them purely for advertising and obnoxious eye candy.

The best use of an animated GIF I've seen is at : http://www.ibanez.co.jp/world/guitar/uv_jem/pages/ uv777p.html [ibanez.co.jp] - the little animation of the selector switch and pickups at the bottom is a fantastic way of conveying a large amount of information in a very small space.

Re:Sure

Well, then you just use MNG [libpng.org] if you need animation. And if you read the linked page, MNG is superior to animated GIFs in a number of ways, one of which is better compression. Another advantage to MNG is it's not necessarily tied to one image format. The individual images can be stored in either PNG or JPEG format.

Personally, I think it's a good thing to have several image formats available with wide support in all browsers. The reason for this is it allows developers to choose which format provides the best results for what they're doing. This means which ones look better and compress better for a certain image. It's definitely a good thing that the patent on GIF is expiring, but it's also a good thing to make sure that PNG doesn't go away, either.

i've burned all my gifs

to cd

Let's face it

You can't get rid of a graphics file format once it's out there.

Re:Let's face it

I know. I even see ANSI graphics now and then. ;)

GIF and PNG are completely different!

GIFs are limited to 8-bit colour depth, no alpha layer etc. etc. PNG is a standardised, open format with support for lossless encoding of full colour graphics with transparencies.

Saying that GIF becoming patent unencumbered is going to reduce use of PNG is like implying that when the original patents ran out on horses & carriages people gave up their cars and reverted. Ain't gonna happen :)

Re:GIF and PNG are completely different!

Slashdot uses gifs. In fact, it seems more likely for the janitors to spell-check than it does for them to convert to png.

Re:GIF and PNG are completely different!

The mistaken belief that GIF has a limit of 256 colors probably comes from the way GIF was first used when it came out. In the late 1980's, PC video cards generally supported no more than 256 colors. Image exchanges were becoming popular among BBS systems and the Internet and viewer programs were quickly produced. No one tried or needed to generate images with more than 256 colors since they could not be viewed on anything less than high priced graphics workstations. Programs that converted images to GIF worked up a number of methods to reduce the number of colors to 256 or fewer. Some actually did a very good job. GIF files were constructed with just a single image block, even though the GIF standard placed no limit on the number of blocks. Since there was no use for more than 256 colors, there was no use for more than one image block. This practice became effectively ingrained into the computer culture and eventually everyone "knew" that GIF supported no more than 256 colors. The fact is, the programs that generated GIF files supported no more than one image block, and thus didn't have a means to deal with more than 256 colors. The top image shows that a GIF file really can have more than 256 colors.

this info and more (including full color GIF) from here [ipal.org].

Re:GIF and PNG are completely different!

The mistaken belief that GIF has a limit of 256 colors probably comes from the way GIF was first used when it came out.

Err, I would say this belief comes from someplace else, like... the GIF specification. GIF has been designed for 256 colors, as the Global Color Table and Local Color Table (which are made a of power-of-two number of entries limited to 256) clearly show.

The site you mention is the homepage for a hack. Yes, a clever dude can create GIFs that look like they have more than 256 colors... but the fact is, such a GIF is made of many 256-colors images. Totally inefficient, compared to PNG, as the author of the hack admits, at the bottom of his page.

That said, there's another well-known GIF hack, which also uses several images per GIF: animated GIF. Let's not forget that, as the spec says, The Graphics Interchange Format is not intended as a platform for animation, even though it can be done in a limited way.

So, let's hope the nightmare doesn't come true, and that horrible multi-image true-color true-Bad GIFs begin to be popular.

PNG is better than GIF in every technical aspect.

GIF Spec: here [msg.net]

Wrong!

If you're getting larger file sizes with PNG, then you're using a program that creates PNG poorly.

When I converted all the graphics on my site over from GIF to PNG, I saved bandwidth. If I did my comic in GIF instead of PNG, the graphics would be much larger than they are now.

use pngcrush or some other kind of tool to optimize them if your stuck using an older version of Photoshop (some versions of photoshop have lousy PNG support) or get some shareware or free software program that supports PNG properly.

JPEGS will still be better for 24 bit color images, but with the right program PNGs will beat out GIFs.

Re:Wrong!

All 3 of the graphics programs I use routinely creat PNG's that are larger than gif's, now this may not be a problem with the format persee, but it is a problem with the real world implementations that are out there and are being used. It doesn't matter for a hill of beans how cool a format is on paper if the implementations suck, if the graphics programs are creating bloated PNG's and the large leader in the web browser space renders them incorrectly it is unlikely that there will be a rush to adopt the format. Like I said I understand that it is a superior format for some things but for most people there just isn't much incentive to switch.

Re:Wrong!

What colour depth are you saving PNGs as? If you're saving them as anything more than 8-bit, it's very likely that they'll be larger than GIFs.

As for IE not working, that's IE's fault and if we pussyfoot around a sucky implementation, we'll be stuck with substandard images. If we use enough PNGs on web sites and tell people that any rendering problem is IE's fault we'll hopefully either (a) encourage the use of non-IE browsers (e.g. Opera or Mozilla) or (b) force MS to fix IE.

Re:Wrong!

Oh come on now. "As a web designer". You can replace your GIFs with PNGs lacking alpha any time you want. They look FINE on IE.

Try out http://www.hazardmaps.gov. No GIFs in sight/site (well, maybe some in the legend area).

You're just lazy if you use GIFs.

PNGs will always be larger than GIFs...

... if saved as truecolour images. What really killed PNG, imnsho, was that the first graphics programs that implemented it simply did not allow users to create indexed PNG files. An 8-bit PNG image is smaller than an 8-bit GIF.

What many people also seem to forget, is that there is no excuse not to safe your PNG image with maximum compression once you are done editing: there will be no image quality loss.

And of course anyone seriously creating PNG images cannot do without PNGCrush [sourceforge.net], which can shave off every single bit of bloat. A crushed PNG image will look just as good as the original, but will be only a fraction of its size, and will be a lot smaller than a GIF would (1).

1: But not smaller than the JPEG. Lossless compression cannot compete with JPEG's lossy compression, and JPEG is still the format of choice for photographic images. For everything else you can and should use PNG.

Re:PNGs will always be larger than GIFs...

What really killed PNG, imnsho, was that the first graphics programs that implemented it simply did not allow users to create indexed PNG files.

Ummm, where did you get your information from? I'm one of the PNG spec co-authors, although my involvement with the project tapered off years ago, and I wrote one of the first commercial implementations of PNG. You may have heard of a company called MasterSoft that used to produce document and graphic conversion utilities. When we were acquired by Frame, and then Frame was acquired by Adobe, our products got released for a while as "Adobe File Utilities by MasterSoft." Quite a mouthfull, but accurate.

My PNG writing code handled indexed (palette based) and truecolor images equally well, and preserved whatever format/color depth was suggested by the original image. As I understand it, my code made its way into several products later on, although it was probably changed.

One of the utilities that came out early on was a small freeware/open source program designed to take GIF files and convert them to PNG. One of the other spec authors cooked that one up, and it worked very well. It created indexed PNG images by default.

While it's true that the PNG spec doesn't exactly demand that you write an indexed color image when the source data is best represented with indexed color, my early survey of PNG-supporting applications seemed to suggest to me that most PNG writing code out there generated good indexed color PNG images. So I'm not sure where this notion came from that the first programs to implement PNG didn't write indexed color. That doesn't jive with my experience.

I have noticed that some applications will generate truecolor PNG images unless you force your application to use indexed color, or downconvert from 24-bit color to indexed color. That's a function of the application software (usually image editing software) not second-guessing the intent of the user. If you've got your application set to do all editing in a 24-bit RGB color space (and some applications will promote loaded images to 24-bit RGB regardless of the pixel format of the original image), don't be surprised when you go to save as PNG and the resulting file contains 24-bit RGB pixels. Downconvert to an indexed color palette before saving. Some application software supports downconversion to indexed color during the save process.

Re:Wrong!

All 3 of the graphics programs I use routinely creat PNG's that are larger than gif's, now this may not be a problem with the format persee, but it is a problem with the real world implementations that are out there and are being used.

You should consider another possibility: you don't know what you're doing.

Do you know the difference between a 24-bit true color and an 8-bit palette image? (This is not an insult or rhetorical question, it's a real question-- you may.) Many image processors and paint programs work naturally in 24-bits. If you save to PNG, they will then naturally save those images in 24-bit format. To save to GIF, though, they must first be converted to 8-bit palette format. With (for example) the Gimp, you have to do this explicitly, so you'll know you're doing it. However, it's possible that some paint programs may do it automatically, without telling you it's been done. This will make for smaller files, but information has been lost. When you read it back in, you will only have 246 different colors in the image, regardless of how many where there originally. If you read the PNG back in, the image will be exactly as you saved it. (Unless you had all sorts of complicated layers, in which case you need an even heavier file format.)

PNG can save images in 8-bit format, in which case a good implementation will give you an image about the same size or a bit smaller than a GIF image. But they don't have to. GIF images have to be saved that way. Naturally, saving an image in 24-bit format will create a larger file than saving one in 8-bit format. (And, it may be different by more than a factor of 3, for reasons having to do with the compression algorithm.)

Before comparing the merits of image formats looking just at the file sizes saved, you have to make sure you understand what is being saved.

JPG is a whole 'nuther ball of wax. That's a 24-bit image format, but it's lossy. That's why they can be so small. But, again, if you read the image back in, it won't be exactly the same; some colors will have been modified slightly. (How much depends on the quality setting you used when saving the JPEG image.) If you're expecting to read and write an image repeatedly, JPEG is a bad format to use, as each time you read and write it, more information gets lost. In that case, you're much better off using PNG images.

-Rob

Re:problems with PNG

large file size versus GIF or JPEG? Hardly. Take a 24 bit RGB image as your source, and find the format that provides the best reproduction of the original image in the least amount of space. PNG wins hands down. GIF can't reproduce the colour depth, JPEG can't reproduce the original pixels reliably without balloning the file size way beyond the PNG.

PNG is actually about the best lossless image format out there - better compression than TIFF LZW, and just as flexible.

BMF kicks PNG's sorry arse

Hahaha no. PNG is nowhere near the best lossless image format. Have you ever heard of BMF? PNG is routinely 40% larger than BMF. You can read an informed, scientific comparison of many formats at The Art of Lossless Image Compression [virtualave.net] (warning: there's an annoying pop-up. Oh well)

Re:problems with PNG

large file size- much larger than gif or jpg

Not really. Some encoders are pretty poor, but an 8 bit PNG can easily rival, if not beat it's gif counterpart.

Let's pick a quick example:

-rw-r--r-- 1 freaky None 27382 Jun 9 10:12 states_imgmap.gif
-rw-r--r-- 1 freaky None 23176 Jun 9 13:28 states_imgmap.png
-rw-r--r-- 1 freaky None 22619 Jun 9 13:29 states_imgmap_pngcrush.png
-rw-r--r-- 1 freaky None 21404 Jun 9 13:31 states_imgmap_pngout.png

The .png is saved from Paint Shop Pro 7, _pngcrush.png using bog-standard pngcrush [sourceforge.net] (which was, btw, identical to pngcrush -brute), , and _pngout.png using pngout [advsys.net].

If you think this is too simple an image, let's try a screengrab of my desktop, reduced to 256 colours. Feeling lucky?

-rw-r--r-- 1 freaky None 342508 May 31 02:22 grab_orig.png
-rw-r--r-- 1 freaky None 136461 Jun 9 13:41 grab.gif
-rw-r--r-- 1 freaky None 97538 Jun 9 13:40 grab.png
-rw-r--r-- 1 freaky None 95336 Jun 9 13:42 grab_pngcrush.png
-rw-r--r-- 1 freaky None 87168 Jun 9 13:44 grab_pngout.png

Same deal as above. The original [aagh.net] is a 24bit pngcrushed file. None were saved as interlaced/progressive, nor with any transparency.

I dunno about you, but PNG looks pretty good to me.

Remember that most PNG's are likely to be 24 bits, as opposed to GIF's maximum of 8, and can even include an extra 8 bits of alpha transparency.

poor standardization

What? There's at least one free high quality reference implementation [libpng.org] anyone's welcome to use (even Microsoft), the full specification [libpng.org]'s there for anyone to read, there's a W3C recommendation [w3.org] that's actively maintained [w3.org]. What more standardization do you need?

Yes, IE doesn't support alpha transparency (something GIF doesn't even have the potential to do; PNG's 8 bit alpha channel is as big as GIF's entire range!), but for general use PNG's a perfect replacement for GIF.

JPEG can beat both, but only if you don't mind it dropping image quality to do so; not something you want to do generally.

little exposure

So what? Most users can just double click on the image file (who's file extension Windows helpfully hides by default) and won't notice the difference. And if some so called "web developer" hasn't heard of it, well, sucks to be him and his clients.

PNG is good

I don't know why more people don't use PNG. It's a great format. For photorealistic images JPG is best, but for logos or other types of graphics and drawings, PNG is great. I hope that we start seeing widespread use of vector-based graphics in the near future, though.

Beta was better than VHS

Just because PNG is 'better' than GIF, doesn't mean it'll win.

GIF has such a huge head start...

Its already moribund

Until IE fully supports the format, it might as well be dead. Nobody who wants the Alpha Channel support can use it in IE6 so it pretty much just sits there, an unused option.

Since IE apparently won't be getting an update until the next version of Windows, I don't see much changing.

It also doesn't help that creating PNGs with Alpha Channels isn't as easy as it can be in some apps.

Re:Its already moribund

Apple's Quicktime can become the default plug in for PNGs and display them instead of IE within IE. Therefore full advantage can be made of Alpha channels. Obviously not everyone has QuickTime installed.

no animation support, but...

Only thing GIF has what PNG does not is animation support... PNG wins in everything else. And most of the GIF animations I have seen do nothing else than annoy so i'm not sure if the lack of it in PNG is a good or bad thing after all.

PNG has more features

PNG is not just an alternative to GIF. PNG has things like Alpha Blending, Gamma Correction and Huge color depth (up to 48 bits, I believe).

So you can really do a lot of cool things with PNG that you can't do with GIF's.

The problem is that without browser support this is like having a CD library in the 70s... Useless. And as long as browsers don't handle PNG's properly it's also chicken & egg problem.

I hate to say it, but we're pretty much at Microsoft's mercy with mainstream PNG usage.

Just removed all the GIF's from my project, rats!

At the weekend I removed all the GIF's from my project and replaced them with PNG's, because I'd had a submission (understadably) rejected to savannah.gnu.org because of this issue.

I'd only been using GIF's because my project outputs web pages and uses transparent images to render a nice customisable user interface (e.g. tabs) in a way that can only be achived with transparent images - and realistically most people use IE and it has problems with PNG transparency that would require me to use lots of VB scripting in IE just to get IE to behave in the manner I wanted.

Does this mean free GNU projects will be able to use GIF's, or are there still other parent related issues with GIF images?

Technical Merits...

My hope would be that at this point PNG can stand on its own technical merits, rather then on ideological merits.

It certainly does for me. PNG tends to display colors more accurately than GIF, has cleaner dithering, and has much better transparency than GIF. It also generates smaller files for complex/large images. But, Internet Explorer once again holds us back. IE doesn't do transparency AT ALL for PNG images. It doesn't even use the page color, or white, just a flat 50% gray. Once IE supports PNG properly, a lot more web developers will feel comfortable using it. Curse you and your "standards", Microsoft.

Jasin Natael

Re:Technical Merits...

That works great for "My First Homepage", but it falls flat on it's face for commercial sites. I can't imagine trying to explain to my business sponsors (who pay my wages) that the reason our site looks crappy to 99% of our clients is that we're using a better image format. I may as well just fire myself...

Whilst I agree with you completely in a technical sense (and in an ideal world), you can't lose site of the practicalities - people are not going to switch browser just to view our site - they'll just go somewhere else. It is essential that our site looks how it is supposed to look to the vast majority of clients, and that, alas, means IE5+.

PNG will stick

IIRC, GIF really specialized in 256-color paletted images, and any extensions to that along the lines of full 32-bit color were kind of a hack, and were never very popular. PNG, on the other hand, is a great compressed lossless format that seems to cleanly support 4 channels. I've used it plenty when storing graphics for programming purposes, and have never had any kind of problems.

It seems that the only reason GIF was around in the first place is because computers were slow, and then later (instead of lossy jpegs) for displaying little images with text in them in web pages. Since PNG does that now and does it better, I think there's no reason to ever go back to GIF.

Sure, the readers and writers might now be legally free or whatever, but anyone who really wanted to use GIFs has been able to do it anyway (it's not like all along Photoshop wasn't able to export, and Explorer and Netscape weren't able to view them), and there is support for better formats pretty much everywhere now, that I don't foresee any changes in the status quo regarding GIF use.

You mean the US patent expires

Unisys claim to have a whole host of patents around the world covering the LZW technology.

You may wish to look at this thread [google.com] on comp.compression

Just as we in Europe are often affected by US patents, even thought he patent itself isn't valid here, now might be your turn to be affected by patents outside your jurisdiction.

A minor 'hack' get's fuPNG to work in IE though...

I have an include file tricking the transparancy into working here [illnation.com] , but this geezer has done it a more elegant way [ntlworld.com]...

Until IE gets a major update it's the only way to ensure that your PNG stuff works cross-browser. And with PNG's superior colour depth and transpancy there really is no reason to NOT at least toy with using PNG's a little any more...

Part of why PNG hasn't been a big hit

GIF and JPG each do something quite well. GIF is well-suited for the rendering of static elements with a relatively small palette, like webpage design elements. It doesn't support photo-realistic images, but that's OK - a GIF can make a very small, efficient file that can load quickly. And it's been supported since the earliest days of the Internet.

JPG compliments GIF by providing a way to display high-quality photo images, and you can control the size of the rendered file by deciding how much you're willing to discard. Again, it's supported by every editor and browser, and it's been around since the beginnning.

PNG is a superior format to GIF from a technical perspective, and it's not encumbered by the LZW patent. However, from the perspective of most mainstream users, it doesn't solve a problem that actually affects them (they don't know or care about the Unisys patent issue), it isn't perfectly supported by all mainstream browsers and servers in use today, and it's a johnnie-come-lately to the standards wars.

Like it or not (I think it kinda sucks), most web developers seem to do things one of three ways: if they need small static elements they use GIF, for photos they use JPG, and if they need fancy-schmancy stuff they use Flash. And nobody worries whether or not platforms other than Windows with the latest IE can render their site, anyway. So maybe PNG will slowly become more common - it is a better format for the most part than GIF is, and pretty much all current browsers and servers (going forward - not some of the older versions that are still in use) support it pretty well out of the box. Really, what matters most is the bottom line (especially once the LZW patent is dead) - can PNG produce a better browsing experience for a site's users? If it can, it'll get used. If not, then it's dead.

Choosy mothers choose GIF!

Not PNG.

~~~

It's all about consumers.

Back in the day, JPGs were known for better compression, but with graphical loss. GIFs were known for preserving appearance, but with less compression than JPG.

Then PNG comes in...
- Open Source/Open Standard: cool
- Lots of options of graphic artists: cool
- even less compression: suckage, but whatever, people who really care about their net experience these days have broadband

PNG may be superior, but it suffers from being obscure and being too technically oriented. I remember when Animated GIFs were tough to create without a "wizard". I seriously doubt your average consumer will care about the added layers and alpha "stuff" that's supported by the PNG format.

Kind of like how Firebird may be technically superior to, say, Internet Explorer, but very few people know of Firebird, and few among those who do know about it would know how to use all its features. IE just "works" for them.

PNG rocks, but until the likes of many Photo CD "developing" companies and other consumer-oriented image business start using the PNG format, people will still only know a world of GIFs, JPGs, and BMPs.

The unfortunate truth

is that PNG will never see large scale use until all of it's features are supported in IE. I would love to use PNG for everything, except that they look like hell in IE. And as much as I badger people about using Mozilla, they don't.

GIF does have full support in IE, and nobody seems to know that the patent even exists. Even those that do rarely care enough to even tell one person.

This is the truth and it sucks. PNG, better in every way, suffers for it.

Animated PNGs?

Does such a thing exist? Will it ever exist?

The way I see it, if I have an image and it's only 8 bit I'll use a GIF, otherwise I'll use a JPG, unless it contains text that needs to be readable in which case I'll use PNG.

Simple rule of thumb?

What is the future of PNG?

What is the future of PNG?

PONG

another release of xv?

The GIF patent (held by Unisys) will expire on June 20.

Does this mean we might actually see another release of xv [trilon.com]? John Bradley has been holding off on a new release for years because of the GIF patent issue. Ironically, perhaps the best feature that'll be in the new release will be built-in PNG support (as apposed to having to download a patch or a patched copy of xv to get this).

Are there animated PNGs yet?

As far as I can tell, GIF still has that one leg up on PNG. I haven't seen any version of PNG that can do animations and that is supported within a browser. Ideally, I'd still like to see an open source alternative to Flash that would allow one to create animations with synchronized sound. Oh well... I'm part way through my C++ book now. :)

Damn Microsoft anyway.

I wonder if Microsoft's halfhearted support of PNG is deliberate. To be honest, it probably is, in an attempt to undermine open standards.

Ahem. Anyway, PNG is a format which would be superior to GIF in every aspect. Just a few problems...

1) Photoshop's PNG support sucks. It is entirely due to Photoshop that we have this insipid misconception that PNG is larger than GIF; if Photoshop would only compress PNG's decently, people would realize that this is false. Because unfortunately, most people are too lazy to use an optimizer along the lines of pngcrush.

2) IE/Windows' PNG support is awful. As I said, I believe that this is deliberate on Microsoft's part, given that they already have good PNG-handling code (in their AlphaImageLoader filter) and they simply refuse to use it as their default. Now, it is possible to use JavaScript -the scourge of the Net normally, but this is one of those points where it can be genuinely useful- to make IE apply the AlphaImageLoader filter to PNG images, but no one's managed to make a complete drop-in replacement that will apply to all PNG images im a page yet. It can be done, but it hasn't been done yet.

3) MNG support is nonexistent. Even Mozilla, the only browser which ever supported MNG, has removed it. This is a great shame.

Now, in the meantime, there actually is one use for images which PNG is ideally suited for, and where the transparency problems of IE/Win are not an issue: screenshots. The compression is good enough that particularly when dealing with computer-generated images, the file size isn't that much greater than JPEG, but there is no loss in image quality, which is especially important when grabbing screenshots of games or video. Screenshots are not transparent, as a rule, so IE/Windows has no problems. Unfortunately, it seems that this use of PNG has yet to be discovered by the mainstream.

PNG may also be good for certain types of wallpapeers, such as most computer-generated graphics or hand-drawn animation. Colors in these generally aren't as complex as they are in photographs, and the lossless compression of PNG works well under those conditions. Combine this with the fact that JPEG (the current de facto standard for wallpapers) has an inexplicable and yet undeniable hatred for the color red, and you have something which can better preserve these types of images. Worth considering, anyway.

Code to use PNGs in IE in a drop-in fashion

// The following is hereby placed in the public domain. The right to copy and modify is
// irrevokably granted to all.
// Copyright (c) Daniel Potter
//
// In your onLoad event, call "msiePngHack()" to watch all your PNG images
// be set to use transparency. (Note that your PNG files must end with
// a ".png" extension and is case sensetive - this is because the MIME type
// is not exposed to the JS code. If you have a file that does not end in
// ".png" then add something like "?f=.png" to the end to fake out this
// script - and certain versions of IE :) )

var isIE = navigator.appName == "Microsoft Internet Explorer";
// if really Opera, this is corrected later

// Sets a PNG image browser-independently (use for roll over effects etc)
function setPngImage(img, src) {
if (isIE && isPng(src)) {
// need to do PNG hack
img.width = img.offsetWidth;
img.height = img.offsetHeight;
// correct this to point to a blank GIF file
/* SLASHDOT ONLY: REMOVE THE SPACES IN THE STRINGS. These are intended to prevent "page widening" but screw up the code :) */
img.src = "http://www.microsoft.com/homepage/gif/1ptrans.gif ";
img.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoade r(sizingMethod='scale')";
img.filters(0).src = src;
} else
img.src = src;
}

// checks if the image is a PNG - ends in ".png"
function isPng(src) {
return src.length > 4 && src.substring(src.length - 4) == ".png"
}

function msiePngHack() {
// just go through the images collection, and "set" the PNGs using the PNG hack
// "setPngImage" method to make MSIE happy
for (i = 0; i < document.images.length; i++) {
var img = document.images[i];
try {
if (!(img.filters)) {
isIE = false;
return;
}
} catch (ex) {
isIE = false;
return;
}
setPngImage(img, img.src);
}
}

Slashdot

Maybe the answer to whether it will fail or not lies in possibly the largest geek site on the web?

wget http://www.slashdot.org
14:12:33 (30.08 KB/s) - `index.html' saved [39023]
grep -i "\.png" index.html | wc -l
0
grep -i "\.gif" index.html | wc -l
32

Food for thought.

PNG never really took off

I didn't discover what PNG was until I discovered OSS. Prior to that I found GIF format files everywhere. I still do.

PNG Is So Much Better Than PBM, PNM, etc.

PNG allows up to 16-bits per channel and has full alpha last time I checked. It can store just about anything, and it's non-lossy.

OTOH, you've got the tools that are supposed to allow you to have only 2n image converters, but the interchange formats for that (PPM, PBM, PNM, others?) seem to always have some shortcoming, and they always have to introduce yet another interchange format! PNG does it all in one neat little compressed format.

So forget about scrapping GIF in favor of PNG. Instead, scrap PPM, etc. in favor of PNG. If it doesn't support it already, PNG could be made to support arbitrary bit depth, and arbitrary channels (inverse hyperkinetic bump blending, or whatever you can imagine).

For the web, in most cases, PNG's capabilities don't add much--unless you are doing something really flashy with your website, in which case you probably use Flash, in which case you have nothing meaningful to say so I ignore you anyway. :)

At any rate, PNGs (at least the RGB channels) are properly supported by all the major browsers, so if something happens to compress better in PNG, or if you really need full color depth in a non-lossy image, why not use PNG?

That about sums it up: GIF--color depth not important, crisp lines important, compression important. JPEG--color depth important, crisp lines not important, compression important. PNG--color depth and crisp lines both important, compression not as important (or the image just happens to compress well with PNG).

In some ways, this is a variation on the "better, faster, cheaper" dilemma.

Now, the scenario that favors PNG may be less common, but it's nice to know we can reach for it when we need it.

Well I'll tell you something

PNG never got a grip on the animation thing.

If you wanted a moving image in a little loop, it was GIF everytime.

PNG could be better?

Even if PNG was a lousy format, it's gotten enough use
that it's here to stay. Fortunately, it's a pretty good
format.

What I wonder is if superior compression techniques, e.g.
LOCO/JPEG-LS will be incorporated into PNG? I was one of
the founders of PNG in 1995, but that was eight years of
technology development ago. Has someone tested PNG
against JPEG-LS in various real world applications?

Other Bad News for PNG

In other news, Mozilla dropped support for MNG/JNG (animated PNG/JPEG-like PNG) in its 1.5 branch. Mozilla 1.4 will support it, but unless someone steps up as a full time maintainer, 1.5 will not. Basically, the old maintainer felt that MNG/JNG support wasn't worthwhile, especially because its library took up as much space as the entire imglib -- roughly 240KB on Windows and 170KB on Linux. With some integration they were able to get it down to 135KB, but it stopped around there.

To be honest, that *is* quite a lot of space for just one format decoder to take. The decoder's writers should get a pat on the back though, because this was still the first MNG/JNG decoder with full support for the spec. (For those who were wondering, JNG is a subformat of MNG and provides non-animated JPEG-compressed images with alpha transparency. Supporting it requires only a few KB extra if MNG is already supported)

MNG/JNG was never used very much on the web, but neither was PNG before a few browsers started supporting it. Clearly if Mozilla drops support MNG/JNG will be dead in the water. In particular, the format provides 8-bit transparency with *animation*, which you would be hard pressed to find in any other open, web-optimized format.

Many theme authors used MNG to produce animated icons that blended with the background (The Mozilla Firebird throbber used one, in fact.) Now they will have to jump through hoops to get this feature. Or they will have to emulate it using GIF's (blegh.)

So far there have been a lot of complaints from the community about the removal of MNG/JNG, but in comparison, very little action. One person submitted an XPI (installer) to allow 1.5/nightlies users to regain MNG/JNG support, but obviously this is suboptimal -- for the format to gain popularity it's going to at least need to be in the default install! Interested persons should check out these bugs on Bugzilla:
(#195280) Removal of MNG/JNG support [mozilla.org]
(#18574) restore support for MNG animation format and JNG image format [mozilla.org]
Adam

PNG is already widely used in multimedia

All rich media content developers have adopted PNG for may reasons.

One of the better ones is alpha transparency with small file sizes. This is a godsend for developers wanting a seamless anti-aliasing against any other background colour for multi-media and web (except of course for good old microsoft, who STILL don't support PNG transparencey - wonder why ? ;))

PNG is not going to go away any time soon as it is far more flexible than the GIF format.

Applications like Macromedia Fireworks use PNG as it's default file extension, anabling it to store layers, image slice data, guidelines etc.

Someone's intellectual property expiring??

You mean they didn't lobby congress to extend patent terms by fifty years retroactively? Jeez, don't they know how to do business in the modern world?!

Ade_
/

PNG-JPG

I use PNG as my local format for most images simply because I can then fiddle with layers/text/blending/whatever at some time in the future if need be.

I generally export them to JPG for web use though simply because a quality 80 JPG is STILL smaller than the original PNG by quite some way.

Also means people can't nick my stuff and change the text (not easily) without asking me (in which case I'll happily email them the original PNGs).

PNGs work just fine, thank you, even in IE

A lot of people have been saying stuff like:

• PNGs may be great, but nobody uses them
• PNGs never caught on because IE doesn't support them
• PNGs will never catch on until M$ supports all their features.
• I can't get PNGs to work

The fact of the matter is, PNGs work great as a drop-in replacement for GIFs. If you limit yourself to what GIFs can do, IE 4.x and Netscape 4.x can use them just fine. And those browsers have just about disappeared from old age.

Of course, if you create a 24-bit PNG to compete with an 8-bit GIF, the GIF will be smaller. Otherwise the PNG will be significantly smaller. If you use gamma correction in the PNG, weird things can happen when people have their gamma misconfigured.

In my own tests a year ago, IE 5.5 on Windows and Mac, as well as Netscape 7 and Mozilla (on Windows, Mac and Linux), all browsers did just fine with 8-bit images, 24-bit images, as well as alpha transparency. That last one is really, really cool looking and everyone should try it.

My theory is that few people use PNGs because most of the HTML books out there recommend GIFs because that's what the authors learned and nobody has bothered to correct them.

More info:

• Browser support [libpng.org]
• PNG test suite [libpng.org], to see if your browser works well for PNGs. If you're using IE, don't take my word that PNGs work
• PNG home page [libpng.org]

PNG for grayscale

One underappreciated feature of PNG that I really like is the support of 16b grayscale. While video hardware (at least the hardware I have) won't display more than 256 levels of gray, having the extra data is good for displacement mapping and such in 3D.

(Before anyone says that their 24b video card displays more than 256 grays, consider: grayscale is R = G = B. If you have 8 bits per channel and all three channels need to be equal to form grayscale, that's only 256.)

The problem is that GIF never went away

PNG never took off because GIF never went away.

Despite all the moaning and gnashing of teeth over the GIF patent, every graphics program produced over the past 15 years, including many shareware programs, has included GIF support. The end result was that people were able to continue creating, editing and using GIF files and the average person never even noticed a problem.

PNG alpha channel

PNG is probably the best format out there for full color images w/alpha channel. It's definitely the smallest in this mode.

You can import PNGs into Macromedia Flash and preserve the alpha channel.

What this means is, for instance, you could import an image sequence generated by a rendering package like Lightwave and when you output the Flash, you are left with the equivalent of a JPEG image sequence layer with a perfect alpha channel on the edges. Even though the JPEG introduces blocky artefacting as the compression is ramped up, it doesn't mess up the alpha blending.

There is nothing else I know of that can do something like that.

I really wish JPEG had a mode with an alpha channel but it doesn't.