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Week 7 Homework

Compuserve and GIFs

In 1984 Unisys (at that time Sperry Corporation) won a patent for a type of lossless data compression known as LZW. The successful patent was licensed to many software developers. In 1987 Compuserve introduced GIFs which used the LZW compression technique. However, the company did not obtain a licence.

In 1994 Unisys discovered Compuserve's unauthorized use of LZW and subsequently attempted to levy licensing fees on large commercial online information providers. It was an extremely unpopular move in the online community, and eventually led to the development of the PNG format (Portable Network Graphics). PNG offers better compression and true-color imaging, as well as transparency capability.

Image Optimization for the Web

When creating content for websites, it is critical to consider both the resolution and file size of assets. Users want a page which loads quickly and looks good in a variety of screen sizes. It's important to balance both these considerations to optimize images and foster a good user experience.

Image optimization can include such techniques as minimizing the file size by cropping excess white space, using a minimal number of colors in the image, and choosing the appropriate file format (eg GIF, JPEG, PNG). Photoshop makes it easy with the "Save for Web and Devices" command which previews the image and shows the relevant file size for different file types. In Dreamweaver, the "Edit Image Settings" button in the Property Inspector allows previewing of file formats, color and quality options, and scaling/exporting of an image.

Screen Resolution and Websites

Screen area, or resolution, is measured in pixels, but a pixel is not a fixed measurement. If a screen has an area of 640 x 320 pixels, an image measuring 320 x 160 pixels will display over one quarter of the screen. But if the screen resolution is 1024 x 768, the image will take up only a small fraction of the screen.

As it would be impossible to accommodate all the various screen sizes currently in the marketplace, a good solution is to write code using fluid % sizing, or other relative sizing such as ems, which will adjust in any window. This is called adaptive sizing. Find out the most common screen size of the website's target audience and optimize to this size. Then test to ensure the page works well in both smaller and larger screen sizes. Test it also in browser windows which are not maximized to their full size.

Section 508 Compliancy

Section 508 is the name of the federal code which states that all electronic and information technology developed, procured, maintained, or used by the federal government be accessible to people with disabilities. Technology is deemed to be "accessible" if it can be used as effectively by people with disabilities as by those without.