3.4 Images and Graphics

GIF has a palette of 256 colors and can compress images at a ratio of 2:1 or 3:1 (Lecture Notes, Session 4). When GIF images are compressed, no data is lost. However, because the compressed files are only 1/2 or 1/3 the size of the original, embedding this image format in a website may result in webpages that load slowly.

JPEG has a palette of more than 16 million colors. This format compresses images at a ratio of up to 20:1 (Lecture Notes, Session 4). While this compression rate offers benefits for website design (images load quickly), the disadvantage of this format is that image quality may suffer as some data is lost during compression.

PNG boasts the best of JPEG and GIF. This format has a palette of over 16 million colors. PNG images cannot be compressed as small as a JPEG file, but the added benefit of a lossless compression makes this a useful tool when storing master copies of important images and documents. At present, this format is not supported by all browsers, but the trend indicates that with time, PNG will be a more common graphic format on the WWW (Lecture Notes, Session 4).

During the lab I chose to incorporate JPEG graphics into my website because of the previously mentioned benefits of using the format on webpages. I placed a local JPEG image in my public unix folder and embedded this image on my webpage using the <img src="imageOrig.jpg"> tag. I also embedded two remote images I found on other websites using the <img src=”http://URL”> tag.

In order to determine how libraries are making use of graphics, I visited a number of library websites. I started by running a City University Catalogue Search. The results page incorporated textual data (name of book, author, etc) as well as graphics (image of book cover). This is one of the most basic ways libraries use graphics on their websites. Another use of graphics by a library website is as an embedded image that links to another service (ex. OWWL graphic on the Wood Library homepage). The Boston Public Library uses images on its homepage to highlight current exhibits and upcoming events, thereby creating an interesting and engaging site.