Administration > Environment Variables > APTCOPYGRAPHICEXTS — Specifies Graphic Formats That Should Not Be Converted During Publishing
  
APTCOPYGRAPHICEXTS — Specifies Graphic Formats That Should Not Be Converted During Publishing
Specifies the extensions for each graphic type that should not be converted to another type when publishing. For example, unless specified by APTCOPYGRAPHICEXTS, graphics with .svg extensions will be converted to PNG images when publishing to HTML, the Web, HTML Help, Wireless, PDA, or using XSL. If APTCOPYGRAPHICEXTS includes the svg extension, SVG images will be passed through the publishing process unchanged, rendering as SVG images.
Extensions do not include the preceding period. (That is, use tif, not .tif.) Multiple extensions are separated with commas (and no spaces).
For example,
set APTCOPYGRAPHICEXTS=svg,tif,tiff