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.