on Michael Vorburger's Personal Homepage


ALTifier Web Accessibility Enhancement Tool


October 1998 to February 1999


Download the ALTifier paper in one of the following formats:

ALTifier Paper in MS Word format, 43 pages (234 KB)
ALTifier Paper in PDF format, 43 pages (519 KB)
ALTifier Paper in zipped PostScript format, 43 pages (214 KB)

The ALTifier Paper in HTML format (less nicely formated) is available. You can download the two Win32 Console sample applications, see chapter §2 in the paper for usage instructions:

[DOWNLOAD] alt_filter.exe (76 KB)
[DOWNLOAD] alt_report.exe (82 KB)


The goal of this project was to research and implement tools to generate textual alternatives such as the ALT attribute in IMG and other graphical HTML elements.

Often images and some other HTML tags lack a textual alternative. This makes them inaccessible to screen readers, non-visual/text-only browsers and Braille readers. Adding alternate descriptions for these tags is one important aspect of making pages more accessible.

On one hand, the project focuses on HTML authors with a tool to set ALT texts on a site-wide per-image basis, instead per each occurrence in HTML documents. The idea of this tool is motivate HTML authors to provide ALT text for all images by facilitating this job. A graphical (GUI) and command-line (CLI) version of such an application are presented.

On the other hand, for users surfing on existing sites with lack of ALT text, a filter tool tries to guess ALT text by heuristics. This tool can be used in a proxy server or CGI which filters/transforms HTML and reads pages from the original Web server, inserts missing ALT text by attempting to "guess" it, and sends them on to the Web client.

The heuristics used to guess alternate text range from looking at an image's height & width to identify simple cases such as bullets and rulers, to analyzing hypertext links for extraction of usefull document link titles. The project report gives a detailed description of the implementation and explains design choices.

Keywords: ALT, IMG, HTML, C++, Filtering, W3C, WAI, Web, Accessibility, Braille, Screen Reader, Proxy, CGI, HTML Tool, Blind or Visually Impaired People, User Interface Transformation


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