Archive for January, 2008

Interlacing, Dithering, Transparency and Anti Aliasing

January 31, 2008

You need to be able to describe all of these techniques in the exam however to understand them I think is best to see them actually in use. So, read the descriptions and then look at the powerpoint.


This refers to images which when downloading do not download line by line but appear initially blurry and then become clearer. JPEG supports interlacing. GIF does not.


This is a technique designed to make an image with a low colour depth appear to have a higher colour depth. It mixes pixels from areas of flat colour, together, giving the impression of more colours than are available.


This is the extent to which a part of an image can be made “see through”. Very useful when images are being used together or on top of each other.


This is another technique to make a graphic appear to be of higher quality than it actually is. The jagged edges that can appear on the edge of a graphic are made to appear smoother by adding extra colours and pixels.

anti-aliasing-dithering.jpg compression-interlacing-transparency.jpg

Digital Cameras

January 27, 2008

You need to be able to describe (in a 3 or 4 mark way) the method by which a digital camera captures an image. Generally this should involve the use of the the terms CCD and A/D converter. I find it easiest to break down the process into steps:

1. Light enters the lens of the camera

2. CCD converts the light into voltage

3. The voltage (an analogue signal) is digitised by the Analogue to Digital converter

4. The picture can now be stored on a digital medium (e.g. solid state memory)


Bitmapped graphics

January 24, 2008

We are now looking specifically at Bitmapped graphics and I have shown you a variety of pictures trying to illustrate different things. Lets start with:


Compression means to reduce the file size of something (in this case an image file). There are two categories that compression falls into lossless and lossy.

    • Lossless – no quality is lost
    • Lossy – some quality is lost


This means to view an image while it is downloading. Non-interlaced graphics download a line at a time whereas interlaced images initially appear blurred and appear to come into focus.

All of these ideas are best understood when you see a visual example, so make sure you look at the powerpoint notes below:


Container files and Codecs

January 20, 2008

Lets start with container files. I think these are fairly easy to get your head around (codecs are a bit more complex in my opinion).

Container File

A container file is a single file that has more than one file type in it. Zip files (if you know about them) are a good way of remembering this; you can zip up a load of files into one single (zip) file, as shown below. This is a convenient way to send loads of files at once to someone else (it also allows compression but we are not interested in that at the mo).



Depending on where you look codec stands for Compress/Decompress or Code/Decode. (For the Higher Computing exam consider it to stand for both!). It does what it says on the tin, it encodes a multimedia file in some format (there are lots of different codecs) and then decodes it at the other end (when you play it).


While I remember I don’t think I put this on a blog post (even though I think you are all pretty clear on what streaming is!). Streaming is the viewing of (or listening to) multimedia data while it downloads. It is what we do all the time on video website such as youtube and increasingly on excellent multimedia applications such as the bbc’s iplayer (where you can stream tv from the last week).


Powerpoint Notes for Container Files / Codecs:


Authoring software v.s. Presentation software

January 11, 2008

You should have had a chance to look at some interactive websites created with authoring software (if not, look now here). The things to remember are as follows:

  • Presentation software is easy to learn to use
    • First years do a unit on Powerpoint because the learning curve is not particularly steep
  • Presentation software is limited in what it can create
    • Even if you know what you are doing with Powerpoint it is impossible to make something like this engine interactive diagram
  • Authoring software takes time to learn
    • Courses to learn Macromedia Director cost hundreds of pounds
  • Authoring software can create complex multimedia applications

Have a look at the Powerpoint slides below for more details.


WYSWIG v.s. Text Editors

January 8, 2008

I hope today you learned about the different between WYSIWYG (What You See Is What You Get) applications and text editors. Both can be used to created a multimedia application of some sort (say a webpage).

WYSIWYG lets you see what you are making (as the user will see it) while you are making it. Microsoft Word could be thought of as a WYSIWYG appliacation beacuse you see the document as if it was printed while you are creating it.

Text Editors require you to type in code of some sort that will be turned into the final product at a later stage. If you good at HTML web programming you may find it more precise to create a webpage using a text editor.

Here is an example from Wikipedia (the text is in Latin and often used for checking the layout of a publication):


Of course the one on the left is WYSIWYG and the right a text editor.

Multimedia Application development process

January 7, 2008

We are back. And we have started Multimedia, hooray!

So today, apart from talking about pub quiz machines millionaire-machine.jpgand supermarket fruit and veg counters, we discussed what a multimedia applciation was and the processes that development teams go through when creating them.

The stages are the same as the software development stages but the details within each stage are different:

  • Analysis – looking at who will use the multimedia appliaction, how (touch screen?) and where
  • Design – likely to be done using a more visual method e.g. a storyboardstoryboard.gif
  • Implementation – choose between authoring software (powerful but difficult to learn) and presentation software (easy to learn but not powerful)
  • Testing – checking that the navigation system of your multimedia software work e.g. do all the links work?
  • Documentation – considering the use of a help page inside your multimedia application
  • Evaluation -consider wether or not your multimedia application is succesful, easy to use, well designed.