The EMF Format

EMF or Enhanced Metafile is a format created to replace WMF or Windows Metafile format. EMF is basically a snapshot of a graphic that keeps the same dimensions as the original file no matter where it is displayed. This format is used to store pictures in a standardized form with the ability to be copied from one application to another, so it is considered device-independent. The EMF format is supported by 32-bit and higher versions of Windows like XP, Vista and Windows 7. EMF does not work on any 16-bit operating systems.

1. Contents

   • The EMF format contains variable length records. These records include information like resolution and picture dimensions. The file contains the data required to draw the graphic on the screen without a separate application. Graphic drawing commands, object definitions and properties take up the largest portion of the file.

   Versions

   • The EMF format has evolved throughout different versions. EMZ is the compressed version of the EMF format. The original EMF format is the first version developed that supports the independence of the file without relying on one device. This version contained the drawing commands and objects directly in the format. Extension 1 added pixel format records and supports OpenGL commands. It also gave the format added flexibility to its device independence. Extension 2 gave the format the capability to measure the surface area on the device displaying the file, increasing the ability to display properly.

   Bugs

   • The EMF format is subject to a few errors in Windows. Sometimes the operating system does not handle the font conversions properly when changing an EMF file to a WMF file. The fonts are distorted into different sizes and rotations from the original graphic. The result is a WMF file that does not match the original EMF format. Windows XP or 2003 has a bug that does not print EMF files larger than 2 GB in size. Service Pack 2 updates are used to solve this error.

   Anatomy

   • There are three basic sections to the EMF format. The first record read is the EMF Header. This record contains information on the structure and contents of the file. This includes a description string of the contents and the pixel format descriptor. The next section is the EMF Record which contains several bits of important data. This is where the drawing orders, graphics state information and object definitions are held. The EMF End-of-File signals the end of the file. It is the last record read by the computer. All sections of the EMF file must be present or the computer returns an invalid file error.