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I've been a web developer for quite some time, and I am used to transforming all my designs into the png file format in order to build my webpages. Despite the fact that png, contrary to jpg, allows transparency in the images, is it a better solution?
The question regards page loading time and best webdesign practices, as well as file size versus quality of the images.
What do you think is the best solution to use?
It depends.
PNG is better for crisp images with a low number of colours,
JPG is better for a low-bandwidth image - however it is not as crisp and therefore not very good for GUI.
Generally, JPG is for photos and pictures, whereas PNG (or GIF) is for layout.
You may find this page interesting, as it goes over the basics of PNG vs GIF.
Google has written about it very well. From Selecting the right image format, you can find a flow-chart to make the decision:
Given the ever-rising speed of the average net connection I don't tend to think that page loading time is much of a concern any more [ducks!]; It's really far more useful to think about what you are trying to achieve with the resources you have at your end: For example is bandwidth limited? Then tending towards heavier compression is a no-brainer. Is the graphic content of the site going to expand, ensuring that the cost of server space will increase over time? Then tending towards heavier compression will delay that cost. Is it an art portfolio site? Then -- aha! -- compression artefacts in the sampler work may actually be desirable! Are you trying to flog a game? Then the screenshots should probably be ultra-crisp.
Generally, then, I would repeat what has been said, although perhaps in slightly different language: For site furnishings, which tend to be computer-generated and will be cached for re-use between pages, tend towards png; For site content, which will often be page-specific and likely large and complex enough to mask lossy compression, tend towards jpg.
With specific reference to switching to png where you decide it is appropriate, run everything through PNGCrush as a matter of course -- otherwise they won't get displayed with the colours you expect in every browser and the overall quality of your design will be diminished.
"Given the ever-rising speed of the average net connection I don't tend to think that page loading time is much of a concern any more "
According to the website SEO optimisation, Google rank your website worse if page load time is above 2 seconds, so compression is necessary, especially on new website designs heavy on graphics.
jpg is usually preferred for photographic images that have a lot of subtly different colors. png works well with computer generated graphics.
That's my rule of thumb.
I am a starter and mostly what I do is if the image is too big I make small unless it's a background image. And if it is for layout I choose PNG and JPG for pictures.
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I am having a little issue here. I am a web development major and I am currently building this site for a project I am required to do. I wanted to make it look pretty with a background image. I created the image in Photoshop and saved it to web as a .jpg and it ended up being 58.8k in size.
I am all for websites that load quick for the user, but I am wondering if less than 60k is okay? I checked it on the yslow firefox extension and it loads for me in 96 ms (slightly poor test subject - http://www.speedtest.net/result/1146275377.png)
Is 60k too much, is it a best practice to have images only 10-20k? I HATE it when I see an image loading... it just.. isn't even worth the graphic at that point. Is there quicker ways to load a image of that size? CSS or tag? Or should I not even be worrying about it?
Most browsers load the background image last by default, so you shouldn't have a problem.
How large is too large depends on your hosting set up, the amount of traffic your site gets, and the typical transfer rate of your visitors.
60k seems reasonable to me for an average site with not too many simultaneous visitors. However, bandwidth costs money and this is the reason that you rarely see background images of that size on big sites. On the other hand, youtube regularly streams videos that are thousands of times larger than the background image that you propose. It's impossible to give you precise advice without knowing much more about your site, its hosting solution and it's usage statistics.
Chances are, if you're asking this question, 60k is perfectly fine.
If you want to guarantee that your background image loads first or last you can do:
<script type="text/javascript">
bgimage = new Image();
bgimage.src = "http://www.olhovsky.com/img/cdf97/256fwt1_eg.png";
</script>
Place that code above the body tag to preload the background image. Place it lower in your html document to load it later (e.g. after the </body> tag to load the background last).
And then in the body tag:
<body onload="document.body.background=bgimage.src;">
I don't think 60k is too large although you probably want to look at your likely users and think about what their connection speeds will be like. If you wanted to try and squeeze the file size down as much as possible, try smushing it as well and you might see it drop a little further.
I'm starting to venture out from using jpeg and gif files to png, I was wondering if there were any standards for using png beside IE's lack of support for it. I also want to know if there was any current articles about setting I should be using when optimizing for web? Right now I'm using photoshop to do this, should I be using firework instead?
Which optimizations you use depends on the type of image. If your image contains only few colors, you might use png-8, otherwise you may need png-24. Same goes for the use of transparency/alpha blending.
The Photoshop save for web-feature does a fine job, but when your website has a lot of visitors, you may benefit from using PNGCrush for further compressing your images. You can use the YSlow plugin for FireFox to test how much bandwidth you can save by crushing your images.
Also, you can make use of CSS-sprites if your design allows it. This can result in less (but larger) images and therefore less requests and sometimes less bandwidth. But this doen't depend on the type of images you use.
Png is supported by IE, by the way. Only the alpha-transparency is not supported by IE 6, but there are CSS/Javascript trics to work around that, although they do not work for background images.
I wouldn't quit using jpg. Jpg is very useful when it comes to pictures. Png files are convenient for small images like buttons, graphical elements, and for images with large plain areas, like screenshots.
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I heard from more than a single source that SVG is dying, it is abandoned by Adobe.
How sad! What's will be next alternative to SVG?
SVG is an open standard, developed by W3C. I really don't see it dying any time soon. Just because certain companies decide to drop its use for their commercial products (usually because they need, or feel they need, something more customised), it does not at all mean SVG will disappear on a more global scale.
At the moment, it's undoubtedly the most widely used vector graphics format on the web. Just take for example the images on Wikipedia - for almost all diagrams SVG is either used or there is a notice stating that it should be used. Many other open source projects endorse it in a similar way.
Now, the XAML markup language (part of WPF/Silverligtht) has been seen as a competitor to SVG by some, but truly they only overlap in functionality to a certain degree. (XAML supports lots of other things such as data binding, events, triggers, etc.) Indeed, the general use of XML is much restricted in that browsers don't natively support it (and can't properly, because of the fact that it's tightly bound to MS technologies). I would not even believe that it's strictly a direct competitor to SVG, nor that Microsoft have intended so.
To conclude, I don't think one can envisage SVG dying out until something clearly improved (and open-standard) comes along to replace it. As far as I know, there is nothing like that at the moment.
Check your sources.
A lot of people want SVG "dead". A common way of getting something to happend is by spreading rumours that it has already happend. It's called a self-fullfilling prophecy (wikipedia). Don't buy into it, and please don't actually help those wanting it dead by spreading the rumor further yourself.
Is SVG dead?
No, it has just begun.
What's next?
HTML5, Canvas and SVG in one long glorious love-affair. Get your first-row tickets now!
(Actually here's a youtube video of html5, canvas and svg showing off the infinite resolution inherent in vector graphics. Somewhat lame but real, unlike rumors.)
SVG (Viewer) was abandoned by Adobe ages ago since most browsers support it natively.
Only IE is holding back the technology by not having native support.
Update: IE9 will have both native SVG support and native Canvas support! (Vista and above only though)
If you'd like to show your support for getting IE to support it natively add your vote and comments to these bugs.
https://connect.microsoft.com/IE/feedback/SearchResults.aspx?SearchQuery=SVG
Bring back VML! Just kidding ;) I don't think SVG is dying, but <canvas>'s adoption for HTML5 seems like the way things are going on the web.
I'd like to add my support for SVG. First, I believe that it is widely used in mobile technology though this is through conversations about 2 years ago rather than seeing code. It was one for the first languages developed by W3C to be used over-the-web and has been consistently supported for the last 10 years. I initially thought it would be a killer-app in 1998 and said so, especially since Adobe then had enthusiastic support.
Because SVG is a full XML dialect it can be easily mixed with other XML applications such as XHTML and MathML. It's possible to include XML information in SVG elements so that documents can be fully semantic (i.e. carry a data-meaning as well as a graphical one).
SVG is effectively feature-complete for a 2-D graphics language. There is no technical reason to invent anything else. It does high-quality rendering, animation and can support interaction through its own elements or through Javascript. It is therefore unlikely that major web software manufacturers will NEED to invent anything else.
The main problem is not that SVG is "dying" - it is not - but that it takes a long time for the various companies to converge. When they do I would expect SVG to emerge as a consensus.
Part of the problem is that graphics are not yet seen as a semantic problem - it's often "easier" to inflict a dumb animation on a client than to set up the infrastructure to send semantics over the web and repurpose at the client. But as the semantic web develops then standards such as SVG will be increasingly important. If, for example, you wish to mash-up geographical information then either you use a properietary solution such as GoogleMaps, or you look for a shared standard approach. You can never count on free proprietary solutions in the long run.
Note also that in many areas which receive public funding there is an increasing drive towards Open standards and this is another reason why SVG is well positioned.
Then there's this article posted Friday on Network World, titled EC decision expected to force IE to better support standards. In it, Håkon Wium Lie, Opera's CTO, states
Second, due to the increased competition stemming from the ballot box, browsers will improve their support for standards. This will result in a richer, faster web. For example, I believe that Microsoft's IE will add support for SVG, a standard that all browsers but IE support.
Of course, it's in his best interest to see IE falling in line, but behind, his browser. He gets to be cutting edge, but part of a larger 'standards' crowd.
While this is an question was asked before high res/ retina displays came to be the normal for mobile devices. SVG is having a big come back as vector graphics solves DPI issues on the web. You will be seeing more SVG on the web than before.
Even apple.com menu is svg now days!
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I want to protect only certain numbers that are displayed after each request. There are about 30 such numbers. I was planning to have images generated in the place of those numerbers, but if the image is not warped as with captcha, wont scripts be able to decipher the number anyway? Also, how much of a performance hit would loading images be vs text?
The only way to make sure bad-guys don't get your data is not to share it with anyone. Any other solution is essentially entering an arms race with the screen-scrapers. At one point or another, one of you will find the arms-race too costly to continue. If the data you are sharing has any perceptible value, then probably the screen-scrapers will be very determined.
It's not possible.
You use javascript and encrypt the page, using document.write() calls after decrypting. I either scrape from the browser's display or feed the page through a JS engine to get the output.
You use Flash. I can poke into the flash file and get the values. You encrypt them in the flash and I can just run it then grab the output from the interpreter's display as a sequence of images.
You use images and I can just feed them through an OCR.
You're in an arms race. What you need to do is make your information so useful and your pages so easy to use that you become the authority source. It's also handy to change your output formats regularly to keep up, but screen scrapers can handle that unless you make fairly radical changes. Radical changes drive users away because the page is continually unfamiliar to them.
Your image solution wont' help much, and images are far less efficient. A number is usually only a few bytes long in HTML encoding. Images start at a few hundred bytes and expand to a 1k or more depending on how large you want. Images also will not render in the font the user has selected for their browser window, and are useless to people who use assisted computing devices (visually impaired people).
Apart from the images, you could display the numbers using JavaScript or flash.
You could also use CSS to position individual digits using various combinations of absolute or relative positions.
You could also use JavaScript to help you create these DIV.
The point is just to obfuscate enough that it becomes really hard.
One more solution is to use images of segments or single dots and re-construct the images of the digits using CSS, a bit like a dot-matrix display.
You could litter the source of the page with these absolutely positioned DIVs and again make it more difficult to reconstruct by creating them dynamically.
At any rate, you can't stop a determined scraper from getting to the data: it doesn't take a lot to automate a web browser and take screenshots that can be fed to an OCR.
There is nothing anyone from paying someone pennies to get the data manually anyway.
The point is: how determined are your opponents (user?).
It's a bit like the software protection business: making things hard enough that you would deter casual 'pirates' is not too hard, and it's a fairly good approach in general.
However, if there is much value in the data you present, there is nothing you can really do to protect it.
All you can do it make it hard enough so that casual 'thieves' will prefer to continue paying for your services rather than circumvent it.
Javascript would probably be the easiest to implement, but you could get really creative and have large blocks of numbers with certain ones being viewable by placing layers on top of the invalid numbers, blending the wrong numbers into the background, or making them invisible via css and semi-randomly generated class names.
I can't believe I'm promoting a common malware scripting tactic, but...
You could encode the numbers as encoded Javascript that gets rendered at runtime.
Generate an image containing those numbers and display the image. :-)
I think you guys are being too reactive with these solutions. Javascript, Capcha, even litigation and the DMCA process don't address the complex adaptive nature of web scraping and data theft. Don't you think the "ideal" solution to prevent malicious bots and website scraping would be something working in a real-time proactive mitigation strategy? Very similar to a Content Protection Network. Just say'n.
Examples:
IBM - IBM ISS Data Security Services
DISTIL - www.distil.it
Can you provide a little more detail on what it is you're doing? Certainly there's a performance hit to create an image instead of dumping out the text of a number, but how often would you be doing this per day?
Using JavaScript is the same as using text. It's trivial to reverse engineer.
Use animated numbers using flash. It may not be fool proof but it would make it harder to crack.
What about posting a lot of dummy numbers and showing the right ones with external CSS? Just as long the scraper doesn't start to parse the external CSS.
Don't output the numbers, i.e. prefix
echo $secretNumber;
with //.
For all those that recommend using Javascript, or CSS to obfuscate the numbers, well there's probably a way around it. Firefox has a plugin called abduction. Basically what it does is saves the page to a file as an image. You could probably modify this plugin to save the image, and then analyze the image to find out the secret number that is trying to be hidden.
Basically, if there's enough incentive behind scraping these numbers from the page, then it will be done. Otherwise, just post a regular number, and make it easier on your users so they won't have to worry so much about not being able to copy and paste the number, or other such problems the result from this trickery.
just do something unexpected and weird (different every time) w/ CSS box model. Force them to actually use a browser backed screenscraper.
I don't think this is possible, you can make their job harder (use images as some suggested here) but this is all you can do, you can't stop a determined person from getting the data, if you don't want them to scrape your data, don't publish it, as simple as that ...
Assuming these numbers are updated often (if they aren't then protecting them is completely moot as a human can just transcribe them by hand) you can limit automated scraping via throttling. An automated script would have to hit your site often to check for updates, if you can limit these checks you win, without resorting to obfuscation.
For pointers on throttling see this question.
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Closed 9 years ago.
When doing small icons, header graphics and the like for websites, is it better to use GIFs or PNGs?
Obviously if transparency effects are required, then PNGs are definitely the way to go, and for larger, more photographic images I'd use JPEGs - but for normal web "furniture", which would you recommend and why? It may just be the tools I'm using, but GIF files usually seem to be a bit smaller than a comparible PNG, but using them just seems so 1987.
As a general rule, PNG is never worse, and often better than GIF because of superior compression. There might be some edge cases where GIF is slightly better (because the PNG format may have a slightly larger overhead from metadata) but it's really not worth the worry.
It may just be the tools I'm using, but GIF files usually seem to be a bit smaller than a comparible PNG
That may indeed be due to the encoding tool you use.
/EDIT: Wow, there seem to be a lot of misconceptions about PNG file size. To quote Matt:
There's nothing wrong with GIFs for images with few colours, and as you have noticed they tend to be smaller.
This is a typical encoding mistake and not inherent in the format. You can control the colour depth and make the PNG file as small. Please refer to the relevant section in the Wikipedia article.
Also, lacking support in MSIE6 is blown out of proportion by Chrono:
If you need transparency and can get by with GIFs, then I'd recommend them because IE6 supports them. IE6 doesn't do well with transparent PNGs.
That's wrong. MSIE6 does support PNG transparency. It doesn't support the alpha channel (without a few hacks), though but this is a different matter since GIFs don't have it at all.
The only technical reason to use GIFs instead of PNGs is when use need animation and don't want to rely on other formats.
The W3C mention 3 advantages of PNG over GIF.
• Alpha channels (variable
transparency),
• Cross-platform gamma correction
(control of image brightness) and
color correction
• Two-dimensional interlacing (a
method of progressive display).
Also, have a look at these resources for guidance:
PNG v's GIF (W3C Guidance)
PNG FAQ
Wow, I'm really suprised with all the wrong answers here. PNG-8 will always be smaller than GIF when properly optimized. Just run your PNG-8 files through PngCrush or any of the other PNG optimization routines.
The key things to understand:
PNG8 and GIF are lossless <= 256 colors
PNG8 can always be smaller than GIF
GIF should never be used unless you need animation
and of course,
Use JPG for black&white or full color photographic images
Use PNG for low color, line art, screenshot type images
The main reason to use PNG over GIF from a legal standpoint is covered here:
http://www.cloanto.com/users/mcb/19950127giflzw.html
The patents have apparently expired as of 2004, but the idea that you can use PNG as open-source over GIF is appealing to many people.
(png open source reference: http://www.linuxtoday.com/news_story.php3?ltsn=1999-09-09-021-04-PS)
Be careful of color shifts when using PNG. This link gives an example, and contains many more links with further explanation:
http://www.hanselman.com/blog/GammaCorrectionAndColorCorrectionPNGIsStillTooHard.aspx
GIF images are not subject to this problem.
I don't think it makes a lot of difference (customers don't care). Personally I would choose PNGs because they are a W3C standard.
Be cautious with the PNG transparency effects: they don't work with IE6.
For images on the web, each format has its pros and cons. For photograph-type images (ie lots and lots of colours, no hard edges) use a JPEG.
For icons and the like, you have a choice between PNG and GIF. GIFs are limited to 256 colours. PNGs can be formatted like GIFs (ie 256 colours, with 1-bit transparency that will work in IE6), but for small images they're slightly larger than GIFs. 24-bit PNGs support both a large gamut, and alpha transparency (although it's troublesome in IE6).
PNGS are your only really sensible choice for things like screenshots (ie, both lots of colours and hard edges), and personally, that's what I stick with most of the time, unless I have something for which JPEG is more suitable (like a photo).
Indexed PNG (less than 256 colors) is actually always smaller than gif, so I use that most of the time.
For computer generated graphics (i.e. drawn by yourself in Photoshop, Gimp, etc.) JPG is out of the question, because it is lossy - i.e. you get random gray pixels. For static images, PNG is better in every way: more colors, scalable transparency (say, 10% transparent, .gif only supports 0% and 100%), but there is a problem that some versions of Internet Explorer don't do PNG transparency correctly, so you get flat non-transparent background that looks ugly. If you don't care about those IE users, go for PNG.
BTW, if you want animations, go for GIF.
PNG is a 100% replacement for GIF files and is supported by all web browsers you are likely to encounter.
There are very, very few situations where GIF would be preferable. The most important one is animation--the GIF89a standard supports animation, and virtually every browser supports it, but the plain old PNG format does not--you would need to use MNG for that, which has limited browser support.
Virtually all browsers support single-bit transparency in PNG files (the type of transparency offered by the GIF format). There is a lack of support in IE6 for PNG's full 8-bit transparency, but that can be rectified for most situations by a little CSS magic.
If your PNG files are coming out larger than equivalent GIF files, it is almost certainly because your source image has more than 256 colors. GIF files are indexed to a maximum palette of 256 colors, while PNG files in most graphics programs are saved by default in a 24-bit lossless format. If file size is more important than accurate colors, save the file as an 8-bit indexed PNG and it should be equivalent to GIF or better.
It is possible to "hack" a GIF file to have more than 256 colors using a combination of animation frames with do-not-replace flags and multiple palettes, but this approach has been virtually forgotten about since the advent of PNG.
A major problem with GIFs are that it is a patent-encumbered format (EDIT: This is apparently no longer true). If you don't care about that, feel free to use GIFs. PNGs have a lot more flexibility over GIFs, particularly in the area of colorspace, but that flexibility often means you'll want to "optimize" the PNGs before publishing them. A web search should uncover tools for your platform for this.
Of course, if you want animation, GIF is the only way to go, since MNG was basically a non-starter for some reason.
"It may just be the tools I'm using, but GIF files usually seem to be a bit smaller than a comparible PNG, but using them just seems so 1987."
It probably is your tools. From the PNG FAQ:
"There are two main reasons behind this phenomenon: comparing apples and oranges (that is, not comparing the same image types), and using bad tools." continued...
But you could always try saving as both (using the same colour depth) and see which comes out smaller.
Of course, if you want to standardise on one graphic format for your site, PNG is likely to be the best one to use.
Personally I use gif's quite a bit for my images, as they work everywhere, obviously your transparency limitation is one key element that would direct someone towards a specific format.
I don't see any downfalls to using gif's.
If they get smaller and you have nothing to gain from using the features PNG offers (which is alpha channel transparency and more than 256 colors) then I see no reason why you should use PNG.
gif files will tend to be a little smaller since they don't support a transparency alpha channel (and maybe for some other reasons). Personally, I don't feel the size difference is really worth worrying about nearly as much as it used to. Most people are using the web with some sort of broadband now, so I doubt they will notice a difference.
It's probably more important to use the type of images that your manipulation tools work best with.
Plus, I like the ability to put an image on any background and have a drop shadow work, which points me more towards the png format.
I usually use gif's because of the size, but there is also png-8 which is 256 colours as well.
If you need fancy semi-transparent stuff then use png-24.
I usually use the 'save for web' feature in photoshop, which lets you fiddle with filetype, number of colours etc and see the result before you save. Of course I would use the smallest possible which still looks good in my eyes.
I use jpg for all non-transparent images. You can control the compression, which I like. I found this web site that compares the two. jpg is smaller and looks better.