How They Work
Here are some techniques that image search engines use to find appropriate
(or sometimes inappropriate) images:
Look for graphics files:
- Search for two HTML tags: IMG SRC and HREF. Both of these may
lead to an image file.
- If the IMG SRC tag is found, the file being referred to is
always an image. If the HREF tags is found, the link that it refers to is
an image if it has an apprpriate file extension, such as *.gif or
*.jpg.
- AltaVista, HotBot, Image Surfer, Lycos
Look for a caption:
- ALT tag in HTML can be used as a caption. It follows the IMG SRC
tag.
- Used to describe an image for users who do not have
graphics-enabled browsers, or those who have turned their enabled feature
off.
- ALT tag is visible when an image is loading and in the source
code for that web page.
Look for web pages that indicate the presence of pictures on that
site:
- Could be stated so in the title of a page.
- Not a very good heuristic.
- Image Surfer
Human intervention:
- Seek out and catalog images.
- Most accurate, but labor-intensive.
- Amazing Picture Machine