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Graphics and Images Tutorial
One
of the biggest complaints with the Internet is that web pages
load too slowly. People don't want to wait while graphics with
large file sizes load. To overcome this problem graphics need to
be compressed.
Graphics for the web are usually in 72dpi resolution this is a
much lower resolution than used in the print industry.
The most common graphic formats supported by web browsers for
compressing graphics are JPEG and GIF.
JPEG - This format is
usually used for photos where there are lots of subtle colour
changes and detail. The JPEG format is a lossy, 24-bit colour,
compression format that generally gives a smaller file size and
better quality for photos.
GIF (Graphic Interchange
Format) - This compression format is usually best suited for
graphic's that have mainly flat colours. The GIF file format is
a loss-less compression format that allows you to select a
palate of up to 256 colours.
When choosing colours for your graphics it is best to use 'Web
Safe Colours' of which there are 216. These are colours that
have been specially selected, as they will look the same on
different systems.
Larger graphics take longer to download, so try to make your
graphics as small as possible. If necessary use thumbnails,
these are smaller images that link to larger versions of
themselves. This way if the user has the choice of waiting the
extra time if they want to see the image in more detail.
Use the 'ALT' tag when you use graphics on your web site. The
'ALT' tag will display a text alternative for the visually
impaired or users that have a text only web browser. |