Photo Optimization is necessary to allow a web page to load in the shortest amount of time possible. Fast loading time require small files. This article discusses the methods used for photo optimization. In an ideal world, a
ca web design could use the highest quality photos and have the webpage download lightening fast. Fast loading requires small file sizes for pictures. Unfortunately, there is a trade off between picture quality and file size. Web surfers are a notoriously impatient bunch. If a website takes too long to load, they will just click away and never come back.
Computer monitors can only display images at 72dpi (dots per inch). So the first step in photo optimization is to reduce the resolution to 72 dpi. Large picture can be sliced up into smaller ones and the put back together on the web page. Each piece will be a very small file and together will load in a fraction of the time a single image file would load.
Most graphic files contain information about the color palette of the image. This information is usually unnecessary for displaying on the web. Many graphic programs included the ability to “Save for the web”. This option discards all of the unnecessary information in the file without any loss of picture quality.
Another method that appears to speed up load time is to use either the GIF or PNG interlaced or the JPEG progressive property. Both of these properties allow the picture to load gradually as first a blurry image that becomes sharper and clearer. In reality the picture actually loads a fraction of a second slower than the regular formats do but it appears to load faster the site visitor.
The HTML <IMG> tag tells the web browser to create a specific sized box to hold the graphic. That way the browser can continue loading the rest of the web page while the graphic file is downloading. If you don’t put the width and height attributes, the web browser must pause until the images are downloaded before it can load the rest of the page.
04-20-2009, 09:01 AM
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