Web Graphics

by Joe Gillespie — Apr 1, 2000

Then there are the pictures. You know the old saying that a picture is worth a thousand words? It's true, but in a different way from what you think. The data that makes up a Web page has to travel along telephone lines character by character, and that takes a certain amount of time. A page that just contains text will load relatively quickly, put a small picture of about two or three inches square, can easily require as much loading time as a thousand words. So, pictures slow down the process dramatically, the bigger the pictures, the slower the download.

Now, if you want to transport soup or orange juice in bulk, you can remove all the water, ship it, and put the water back before you drink it. You are 'dehydrating' the product to reduce its volume and weight. We use much the same idea for Web graphics except that instead of dehydrating pictures, we 'compress' them. They are squashed down, sent along the telephone line, and then decompressed by the browser into their original state, or pretty close to it anyway. What we are doing is making more efficient use of the telephone line time - or 'bandwidth' to give it its technical name. Good use of bandwidth is what Web page 'design' is all about - getting the most information into the smallest possible size. A thousand characters of text uses approximately one thousand bytes of computer data or one kilobyte. (1Kb is actually 1024 bytes, but we won't split hairs). There are, on average, six characters to a word in the English language, so 1Kb will give you approximately 166 words, or a photo about an inch square.

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