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EMF
A metafile is an array of variable-length structures
called metafile records that store a picture in a
device-independent format. The first records in the metafile specify
general information like the resolution of the device on which the
picture was created, the dimensions of the picture, etc. The
remaining records, which make up the bulk of a metafile, correspond
to the graphics device interface (GDI) functions required to draw
the picture. These records are stored in the metafile after a
special metafile device context is created. This metafile device
context (DC) is then used for all drawing operations required to
create the picture. When a GDI function associated with a metafile
DC is processed, the system converts the function into the
appropriate data and stores this data in a record at the end of the
metafile.
After a picture
is complete and the last record is stored, you can pass the metafile
to another application by using the clipboard, Embedding it within
another file, Storing it on disk, or Playing it repeatedly. A
metafile is played when its records are converted to device
commands and processed by the appropriate device.
Device
independence is the one feature that sets metafiles apart from
bitmaps. Unlike a bitmap, a metafile guarantees device independence.
There is a drawback to metafiles however, they are generally drawn
more slowly than bitmaps. Therefore, if an application requires fast
drawing and device independence is not an issue, it should use
bitmaps instead of metafiles.
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