Description Description
...and many other places all over the Web!
Normal polygon-based image mapping programs (like mapper that comes with NCSA HTTPD or the imagemapping capability built into Apache) are awkward when dealing with organic shapes. It's difficult to outline a complex shape with straight lines and then manage these polygons with many points. It's also pretty annoying to work with discontiguous shapes. With normal imagemap programs, you'd need to define a new region for each part of the shape, or overlap shapes in a specific order. That's why I created glorglox.
Now, individual pixels can be mapped to a specific URL!
glorglox actually uses two images. As usual, one image is displayed as an in-line image in your HTML document. The second (auxiliary) image is used to map coordinates on this picture to URLs. When the user clicks on the displayed image, glorglox finds the colour value at that position in the auxiliary image. The auxiliary image is a paletted GIF file, so this value can be from 0-255. Maps can have up to 256 different URLs per imagemap. glorglox reads the specified map file to find the corresponding URL, and returns a pointer to it. (just like NCSA's mapper.)
If you specify "NOWHERE" as the URL in your map file, clicking on a pixel of the specified colour will return the user to the page they came from using the HTTP_REFERER environment variable. If HTTP_REFERER isn't set, they are sent a message telling them to go back.
I dreamed this feature. Yes, that's right, this feature actually came to me in a dream, sometime in the morning of March 15, 1995. Really.
Incidentally, you can get the same functionality in NCSA's mapper simply by using my sendmesg() function instead of theirs.
Error messages include a customizable e-mail address in a mailto: URL so that users with appropriate browsers can report errors immediately. Errors that are probably caused by the user's browser are distinguished as client errors.
glorglox-generated HTML replies include
<HTML>,<HEAD> and <BODY> tags. This was a
new thing when glorglox was originally written!
The program code itself is based directly on NCSA's mapper program version 1.2. If you are currently using NCSA HTTPD and its imagemap program, you can have a (simple) working glorglox image map up and running in under an hour.
glorglox's auxiliary images are now standard GIF files! You'll need to get gd to compile glorglox.
Portions developed at the National Centre for Supercomputing Applications at the University of Illinois at Urbana-Champaign.
GIF support from gd by Thomas Boutell.
J. Eric Mason told me about the nasty strcat errors I inherited from NCSA.
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