Preparing images for use on the Web

This paper describes what I would like you to do to prepare your images for display on the club web site.

First your image has to be reduced in size. This is required to reduce the time it takes for a file to be down loaded from the web server, The smaller the file the faster the down load. The downside of small files is that image quality is compromised. By size I mean "file size" which is directly related to the number of pixels stored in the image file and is measured in Bytes (normally Mbyte or Kbyte).

Later I will add some screen shots of how some software performs this reduction but please note that it has nothing to do with the dpi setting that you may enter. Please use the option to set the longest edge to a number of pixels. You should enter a value of between
1000 and 1920 pixels. The file should be saved as a jpeg with a quality of 60-70%.

How you name your file is important. Desktop computers attempt to protect you the end user from many complexities of computer science and the use of characters in file names is one such complexity. Certain characters should never be or may not be used in file names. The list of illegal characters varies from OS to OS so my list only includes a subset:


A to Z, a to z, 0 to 9


spaces; use an underscore if you must e.g. Fred_Bloggs
punctuation such as ? / \ | . , ; :
Maths type characters e.g. \ / < > % $ £ @ ( ) [ ] { } + - * =


Lets have a look at the humble space character. Now you are probably going to tell me that you have hundreds of files on your computer that have spaces in their names. Yes ? Well I'm afraid that you do not. When you name a file and hit the "enter key" your friendly OS looks at the entry and substitutes %20 for every space. This altered name is the one stored but when, at some later date, the filename is displayed the reverse occurs and a space is substituted for every %20 in the true name.

Why %20 ? All characters on your keyboard have a numeric value. An uppercase "A" has a value of 65 and a "space" has a value of 32. Both these numbers are normal base ten numbers. Computers use binary and a shorthand for binary is base sixteen or hexadecimal. Convert number 32d to base sixteen and the result is 20 (hex). Here is an example of the same file name:

What you see : IS_4V6A3247a Head of Striped Basilisk.jpg

What is stored : IS_4V6A3247a%20Head%20of%20Striped%20Basilisk.jpg

This is the reason that the % character should not be used: all computers read this as an introduction to a numeric code that should be processed.

I think thats enough detail, just use a-Z , 0-9 , _ and all will be fine.

Lastly, it is a help if you add your initials as a prefix to the file name e.g. IS_ in the names displayed above.