Mini-article – Graphics formats Part 2

By | April 5, 2006
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April 2006 Newsletter

Hello – hope you didn’t get too buried in the snow last month!
This month you’ll find out about bitmap graphics in the second part of the article started last time. You’ll also read about downloading sheet music, your PC’s clock and Summer Time and find out what a cache is.
So without further ado, let’s get stuck in…

Mini-article – Graphics formats Part 2
Last month I talked about the two different types of file format – vector images and bitmap images and then went on to tell you a bit more about vector images. This month I’ll give you more detail about bitmap images… you might want to nip back and re-read last month’s article first to refresh your mind. If you haven’t got it, you can find it online at

A bitmap image is a grid of dots and the computer remembers which colour each one is. It also usually stores what size it should be viewed at – if you make it too big you can see the individual dots and it’ll look grainy.
Bitmap formats are often compressed. There are clever ways for the computer to store the graphic without taking up much space. For example if there’s a big area of purple it could just store a big area of purple instead of remembering each dot separately. A lot of the methods of compressing the file do affect the quality but you can compress it quite a bit without the difference being noticeable unless you look closely.

There are lots of formats for bitmap graphics – here are the main ones and what they’re mainly used for:
You can usually tell which format a file is by how its name ends. For example photo.bmp is (wait for it) a bmp file…

bmp – this was originally the main bitmap format in Windows. It gives great quality but big files that take up lots of space so it isn’t used much any more. It is still used for desktop backgrounds and the flying objects screensaver.

Jpeg or jpg – It stands for Joint Photographic Experts Group. They created a format that can compress pictures by different amounts depending on how small you want the file to be vs how good the quality should be. It’s a great format for things like photographs and is probably the most used bitmap graphics format. I would recommend it for your digital photos, especially if you want them to be small files so you can email them.
If you want to email photos you can even open them in your photo editing software and save them with extra compression so they’re nice and small for emailing.

Tif or tiff – Tagged Image File (Format). This is an older format that compressed the picture but didn’t do it as much as jpeg. Some digital cameras and photo editing programs use it. If you’ve got the choice of this or jpeg I’d recommend going for jpeg but if you don’t have the choice tiff will be OK.

Gif – Graphics Interchange Format. This is a file format that’s mainly used for graphics on web pages. When you see a photo or a company logo on a web page, chances are it’s a gif file. Gif files take up a tiny amount of space (so they download very quickly) but don’t really have the quality for your holiday snaps – they tend to restrict the range of colours. You’re unlikely to need to use them unless you’re creating a web page.

So that’s the different formats and what they’re for. The main thing to remember is that whenever you see jpeg, tif, bmp or gif, it’s a graphic like a photo. And if you’re not sure which to use, you can come back to this and have a read to remind yourself!

Download of the month:
I quite often get asked if you can find sheet music on the web. You can but most sites have a specific, limited selection. So there’s a site specifically for classical piano music, another specifically for jazz group music and so on. But here’s a site that lists lots of different sites. It’s particularly handy because it has a list of sites by category and there’s a search facility which (if you set to just search the site, not the whole of the web) you can type Scott Joplin or whoever into and get links to music by them. Nifty!

Reader’s Question
My clock used to set itself to summer time automatically but this time it didn’t. What’s gone wrong?
I’ve heard this from a few people. It’s usually because the PC is set to Internet time. Internet time makes the PC check the actual time on the web and correct its own clock. Which is great since your clock is always right. However, the Internet clocks usually are set to GMT so don’t change to summer time. The solution is either to manually change it to GMT + 1 hour in the internet time settings or to turn internet time off. Then your PC will change to summer time automatically.
You can access the time settings by double-clicking on the clock in the bottom right hand corner of the screen.

NEW feature – Word to the wise
“Cache” (pronounced “cash”)
A cache is a chunk of fast access memory kept closer than the main memory. For example a processor (the brain of the PC) has a cache on it for things it needs to access soon so it doesn’t need to use the main memory, which is a bit slower. This makes things run a LOT faster. Most modern PCs have at least 1MB of cache memory – more is better.
Internet Cache is also used to mean parts of a website downloaded by your PC and stored on the hard drive so you can open that site more quickly again next time.

Have a good Easter and I hope you get to enjoy some proper Spring weather!

Tim Wakeling

All the above © Tim Wakeling 2006

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