Can we use whole page design jpg file as css-sprite without slicing?
You can, but it generally requires a lot of planning and careful development. For example, if you need to add a new icon/image to a page and you suddenly find your sprite image is not big enough, you have to go through and change all images on the page to use whatever new layout you come up with.
No. Most designs includes one or more images which are:
Content images, which should be included with <img> and have suitable alt text.
and/or
Images which tile in 2 dimensions, which can't be sprited.
as mentioned by codeka, you can. but you'll end up with a really big .jpg with a lot of white space if you plan to use the whole page as a sprite without slicing
You also probably don't want to use jpg for everything. Some things are better with jpg, some with png (or gif).
Related
As a web developer, I have to cut a layout similar to this (example website by Ruben Bristian):
Should I bother with cutting multiple small images like a logo:
a label:
and so on? Or should I just make one big background image with all elements like this:
and make a positioned <a href> with display: block; for a linked logo?
A single image has smaller size than multiple elements altogether. What are the other pros and cons?
Use separate images.
Here are a few reasons why:
Maintenance:
It's going to be much easier to maintain in the future, if/when there comes a point when you want to build on what you already have. Furthermore (and subjectively), the background image is not critical to the design. It wouldn't look broken if parts of the background were clipped. It would look broken however, if the logo were distorted.
Bear in mind also that newer, sharper displays are being developed. It's much easier to display the standard resolution background (it's already blurry, so clarity is not essential), and maintain two versions of the logo. One for standard displays, one for HD.
Semantics: What if the user has images disabled? Sure, it's unlikely, but what about Google? You should have some proper markup with real content. Your site needs real textual content in order for Google's crawlers to gather information about it. Use CSS image-replacement techniques to build the interface.
Another note on HD displays:
It's convention to serve larger images to HD (retina) displays, and use CSS to downsize them, effectively increasing their dots-per-inch. If you use just one image, the user will have to download a considerably large image. More bandwidth used by you, and slower experience for your users.
Furthermore, the text will look horrible on HD displays. It makes much more sense to allow the browser to render razor-sharp text to the user.
Accessibility: For a start, screen readers won't have a clue what your site is about. That might not be so relevant in this case, but it's best practice to build and accessible website. If you want to include some smaller text on the site, some users may be unable to read it. Normally they would increase the font-size, but if you use images, they're powerless.
I may have over-dramatised this answer, but the advice is well-intentioned.
I would honestly try a little bit of a different approach. The "photo" part of the image would be one image, the logo another, and maybe the double bar on either side of the heading another (but might not be necessary.
I would use the photo part as a bg image on a div, and within code the rest.
I wouldn't make the text part of the image at all. Try using a service like Google Web Fonts to get a good font.
The approach will save you lots of maintenance time, and also help with performance.
PROS:
Total bytes loaded is lower.
You do not have to worry about how little images are put together to become the total image.
if you just use 1 image you will find that it will be much easier to maintain the fluidity of the layout. You will not have padding/alignment issues, rendering issues, etc. Realistically the load time should be the same either way, maybe a tad longer for multiple images as the browser would have to render more css, but i imagine it would not be very noticable. In the end it really comes down to what is better for the job. I pretty biased towards 1 clean image :)
I guess you have to think about how you are going to use each element individually, and how they are going to change in the future.
You might want to change the logo, animate it, or want to re-use it elsewhere. The background image might change, or become multiple images in some sort of transitional gallery.
If this its never going to change (unlikely), then, yes, flatten it in a single image.
I personally would have as a separate background image. Then perhaps have the logo and the label on another transparent png and utilise css sprites to re-use them throughout the site. This will halve the number of requests required to download the logo/label, and allow you to optimise each image separately ie the complex background photo, and the more simple logo/label.
i want to know about sprite technology used in css regarding fast accessing of the web pages.
They are cool because you can minimize http requests with them and make your page's performance improve. They are considered good in terms of SEO as well. Check out this for more info:
CSS Sprites: What They Are, Why They’re Cool, and How To Use Them
This page gives a pretty good overview.
Essentially it puts all of the page's images into one large image file and then uses CSS to display only parts of that file (to give the effect of multiple images). This has the advantage of only requiring the browser to make one request for all the images rather than a bunch of individual requests (each of which has an overhead).
If you have the group of icons for example , you are creating one jpg or png file and adding the images one after another. Then you just creating the backgrounds based on only one image and fixing it in percentage / pixels view. It makes your code organized and saves images loading time . For example , you have a window and it has close , unfold icon. You can create a png file named windowControlSprite.png that contains two icons one after another , then you can create properties in your css to this element. #somediv {background-position:0px -20px;}
Also, you can find CSS sprite X and Y easily with tools like http://www.getspritexy.com/
Otherwise you need to use image editors like Photoshop or use Firebug to find X and Y coordinates.
I noticed that Digg and Google are using a kind of CSS optimization in their GIF header image. For example digg uses this image:
Why are they using this technique and how to do it in my own site?
These are called CSS sprites. They are used to reduce the number of server requests.
Check out this nice article about them: http://www.alistapart.com/articles/sprites/
CSS Sprites: Image Slicing’s Kiss of Death:
A List Apart
Another article at Smashing
Magazine
A hack to support IE6
The purpose of this technique is to reduce HTTP-requests by combining all images.
It's called a css sprite
I believe these are called splices (or is it sprites); basically they load up the whole image one time and tell CSS to display only part of it, that way they avoid having to (pre)load lots and lots of images.
They add more responsiveness to the page, since consecutive images are loaded immediately.
As weichsel mentioned, check the article # A List Apart.
They use that technique so one image is downloaded rather than the browser potentially making many different connections to download multiple images.
You can then "crop" the image as a CSS background-image using a combination of CSS properties like "background-position" and "width".
The the links the others are posting while I write this probably have good techniques to crop the images.
I want to know when not to use CSS sprites. CSS sprites works great, but are there any occasions when they create a lot of headaches?
Like all things, there are times when it is useful, and there are times when it is harmful.
Many developers like to use CSS sprites because it saves on request time -- the browser makes one request, downloads the image, and all the various sprites are now automatically cached and blazing fast.
So how can it hurt?
Because download size != memory size.
That PNG or GIF that's only 10kb might actually be much, much greater in size once the browser loads it in memory. The issue is that while something like GIF will compress solid areas of color, the browser expands it out to a bitmap, where all images of equal dimensions use equal memory.
And it loads a new bitmap every time you use that image somewhere.
So everything in moderation.
See: http://blog.mozilla.com/webdev/2009/06/22/use-sprites-wisely/ for more info.
Maintainability of your site will suffer from using them. Only combine images that belong to the same logical unit and are unlikely to be updated separately. Keep images that are likely to change separate to begin with.
CSS sprites works bad for <input type="text"> where the user can enter more than fits in the box, as the background then scrolls in some versions of IE.
They also works bad if you want to repeat the pattern.
They can cause headache for your users if they want to download a particular image. First they won't get the "Save image as" option. If they figure out to use "View background image" they'll get a huge image with lots of other images on there too.
This is why sprites are best saved for "utility" (i.e. buttons) or design images.
We had a tough time when we wanted to position the image dynamically.
background-image: url(../images/a.gif);
background-repeat: no-repeat;
background-position: left bottom;
This is tricky (if not impossible) to do using a sprite.
Sprites should never be used when the size of images are very different.
Because in that case the size of sprite is quite huge.
Recently I converted 3.5MB pictures to a sprite, and size shooted up to 17MB!
Using larger pic might be a headache...
When pics are combined in smaller size, and neighbouring pics are just 1 or 2 px between each other, then CSS sprites can be a good solution.
In our case, http://www.nbhuntop.com, we just use it for menu components including: Home, About, Products. And all the pics are in gif format, and no one will download these pics at all.
Has anyone seen tooling, or even a process concept to generate css sprites from an existing website's images, and css during the build process?
I should think the steps would be:
walk an images directory
create a single sprite file from all the images in that directory
for each image
find any css classes using that image
update the css class to use the new sprite file
I'll using asp.net so something in msbuild would be awesome. However, I'm finding little out there even coming close.
You could use this http://spritegen.website-performance.org/ which is BSD licensed code. (see the download link on the right hand side.)
An automatic process like that only works well if you have a few simple images. There are several reasons to do the process manually:
Some image formats work better than others for sprites. If you try to make sprites out of JPEG images the compression will easily bleed from one image to another causing artifacts. Index color formats like GIF and 8-bit PNG has a limited number of colors, so if you put images with too varying color palettes together you will lose colors.
You may want to repeat an image horisontally or vertically, which makes it harder to combine the sprite image.
If the image is smaller than the element that you use it in, you would have to pad the image with transparent pixels. If the size of the element is dynamic in any way, the automatic process would not even know how much padding the image would need.