Everything about Windows Metafile totally explained
Windows Metafile (
WMF) is a
graphics file format on
Microsoft Windows systems, originally designed in the early 1990s and not commonly used after the rise of the
World Wide Web and the widely used graphics formats such as
GIF and
JPEG. It is a
vector graphics format which also allows the inclusion of
raster graphics. Essentially, a WMF file stores a list of function calls that have to be issued to the Windows graphics layer
GDI in order to restore the
image. Since some GDI functions accept
pointers to
callback functions for
error handling, a WMF file may include executable code. It is somewhat similar in purpose and design to the
PostScript format used in the
Unix world.
WMF is a
16-bit format introduced in
Windows 3.0; a newer
32-bit version with additional commands is called
Enhanced Metafile (
EMF).
EMF is also used as a graphics language for printer drivers.
There are also compressed versions of Windows Metafiles known as
Compressed Windows Metafile (WMZ) &
Compressed Windows Enhanced Metafile (EMZ).
(External Link
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SetAbortProc exploit
Exploits using the "SetAbortProc" GDI function were discovered in December 2005. The function, which registers an error handler normally intended for use when a print job is cancelled during
spooling, allows
arbitrary code added to a WMF image to be executed without the permission of the user.
Alternative implementations
The WMF format was designed to be executed by the Windows graphics layer
GDI in order to restore the
image, but as the WMF binary files contain the definition of the
GDI graphic primitives that constitute this
image, it's possible to design alternative libraries that render WMF binary files, or convert them in other graphic formats.
For example, the
Batik library is able to render WMF files and convert them to their
SVG equivalent.
The Vector Graphics package of the
FreeHEP Java library allows to save
Java2D drawings as EMF files.
EMZ is
gzipped EMF.
One program that directly unpacks EMZ and WMZ files into EMF and WMF files is
SpeedCommander 12.
Further Information
Get more info on 'Windows Metafile'.
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