MagicDraw UML offers a wide range of diagram export formats via the menu File>Save as Image.
The W3C's Scalable Vector Graphics (SVG) format is supported, however for online presentation this may exclude some of your audience. From http://en.wikipedia.org/wiki/Scalable_Vector_Graphics:
Support for SVG in web browsers
The use of SVG on the web is in its infancy; there is a great deal
of inertia due to the long-time use of pure raster formats and other
formats like Adobe Flash or Java applets, and browser support for SVG is still uneven. Web sites which serve SVG images, for example Wikipedia, typically also provide the images in a raster format, either automatically by HTTP content negotiation or allowing the user to directly choose the file.
This is also why this eSchool also serves most images as JPEG or PNG.
We compare here file sizes and behavior under scaling of an exported test diagram in MagicDraw UML.
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