9. Optimising graphics

Image files can be fairly large and take up a lot of storage space and memory. This is fine when you are working offline because you can open up the files quickly.

However, you can run into problems with large images when you are online.

How many times have you gone to a web page and seen the text appear quickly but you are left with blank boxes where the pictures should be while they load slowly?

This is because the file size of the image was large and it took time to download.

When you are designing a website, you need to think about the size of your image files. If they are too big, people might get fed up while waiting for them to appear.

You can overcome this problem by trading file size for quality. If you reduce the quality of an image then the file size is smaller and it is much faster to download. This is called 'optimising graphics'.

The problem with optimising graphics is that although you get a smaller file size, you do lose quality and this can spoil the image.

The images on the right show the same image at different quality levels and file sizes. The first one is superb quality but a much larger file. The last one is very poor quality and although the file size is much smaller, the image has been spoilt.

So, the trick is to find a balance between file size and quality - probably the middle image.