GCSE Computing Revision – Compression

The gravestone of J.P.G.

Image via Wikipedia

What is compression?

  • Compression is the process of reducing the bits required to store a file
  • You usually compress things to put them on the internet
  • This is to save bandwidth and speed up the download
  • You normally need to compress pictures to send them in an email
  • Compressing┬áthe picture┬ámeans less information needs to be sent
  • There are two types of compression:

Lossy Compression

  • This type of compression reduces the file size by getting rid of bits and hoping you won’t notice
  • It is used for multimedia: Pictures, music and videos
  • Usually it doesn’t look (or sound) any different because your brain fills in the missing information
  • To compress a picture in this way, the computer looks at pixels next to each other and if they are similar colours, it says they are both the same
  • After doing this, it ends up storing less data
  • The .mp3 music format and .jpg picture format use lossy compression
  • Every time you save something as a .jpg the quality decreases
  • It’s completely evil if you ask me! .jpg isn’t my favourite picture format any more! I’m a .png person now, and this is why:

Lossless Compression

  • In lossless compression, the file size is reduced without losing any quality
  • The original file stays completely unchanged
  • It is used for text, programs and program data (like videogame save data) because they are all things you don’t want to lose small parts of
  • The .png picture format uses lossless compression, which is why it’s my new favourite!

Exam Question

  • I’ve seen two GCSE computing papers which have a question about compression (and that’s quite a lot given that at the time of writing only two GCSE computing papers have ever been published)
  • They both ask for two ways for a kid to reduce the file size of a picture to send it in an email
  • One way is to compress it
  • The other way is to reduce the dimensions of the image (make it less tall and wide)

I tried saving things as .jpg over and over again to create a lossy compression slideshow for you all to enjoy, but I just couldn’t notice any difference! (Stupid brain, filling in!)
Sorry about that.

Return 0; //The end.


About Matt

I like writing, filmmaking, programming and gaming, and prefer creating media to consuming it. On the topic of consumption, I'm also a big fan of eating.
This entry was posted in GCSE Computing Revision and tagged , , , , , , , , . Bookmark the permalink.

One Response to GCSE Computing Revision – Compression

  1. Pingback: SMART, Financial and Non-Financial Objectives – GCSE Business Studies Revision | Matt's blog

Enter comment:

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s