Metafiles
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Dialog Box: Metafiles [ File Menu ]

---- Windows Only ----------

Windows metafiles are basically vector images (but including fills) that can be rescaled without necessarily losing resolution. They record the drawing commands that are used for the screen or standard printer output, but the result may depend on the software or device for which they are intended. A metafile image may either be saved in the Clipboard, to be Pasted into another application, or written to a file.

CRYSCON can write three types of metafiles. The original or Standard metafile format has proven inadequate for transmitting scaling information, and many applications do not even accept Standard metafiles. Placeable metafiles, a format which was originated by Aldus Corporation, contain scaling information in an additional header. The standard and placeable metafiles have the .WMF extension. WMF or standard files are 16-bit format, i.e. use 2-byte integers. Enhanced metafiles are 32-bit format files which also contain scaling information. They are the preferred type of metafile for use in 32-bit Windows systems (Windows NT or Windows 95), but cannot be used in standard 16-bit Windows 3.1or Win32s.

Original (16-bit or .WMF) metafiles can be written with either of two Scaling Modes; Isotropic or Anisotropic. Isotropic supposedly keeps the same proportions. Generally, Isotropic is the best as it allows rescaling while preserving proportions. However, some applications only accept Anisotropic files, and some ignore the scaling mode completely.

When writing to a file, to prevent loss of resolution, CRYSCON uses a standard scaling of 2540 dots or pixels per inch (1000/cm). However, some drawing applications may not read the scaling correctly (assuming 72 dpi) and it may be necessary to rescale the drawing after importation.

When writing to the clipboard, CRYSCON uses the current screen resolution, which usually is about 92 dpi. This is because most drawing applications assume screen resolution or 72 dpi. The clipboard image can be either 16-bit (.wmf) or 32-bit (.emf) according to the setting of the Type option.

See Frames for details of the frame and frame units.

Limitations of Metafiles. As designed and implemented by Microsoft, the metafile allows recording of all Windows drawing commands, so that a file image can be a copy of what is shown on the screen but rescalable. Unfortunately non-Microsoft drawing applications (e.g. Corel Draw, Adobe Illustrator) sometimes implement metafiles incompletely or incorrectly so that there are some limitations in metafiles written by this option, in order to allow them to work in as many applications as possible. It many be necessary to try many combinations of settings (Destination, Scaling mode, Type of file) to get satisfactory results in an importing program.

1) Resolution for the clipboard is now that of the screen, typically 72-96 dots-per-inch (dpi) - earlier versions of ATOMS used 2540 dpi. The lower resolution should not cause problems except for very complex drawings - if a drawing looks good on the screen, it should look good in a document. If the clipboard is unsatisfactory use a file.

2) Bitmap patterns for black-and-white images cannot be used. Fills are transmitted as gray shades which are interpreted by the importing application and/or printer.

3) A background is always present, to insure correct scaling. With some care, this drawing element may be removed in importing applications.

4) There is no clipping of the image, although some importing applications may use the drawing frame for clipping.

5) Transmission of the image in Corel Draw with the Clipboard may require use of Edit/Paste Special rather than a simple Paste.

6) Adobe Illustrator generally does not do well with labels - is may be necessary to use an EPS file for Adobe Illustrator. Label backgrounds may not be transmitted in other applications.

If a metafile is not satisfactory, a raster file can be used. PNG raster files are often smaller than metafiles, especially for complex drawings. Also, many drawing programs now support import of EPS (Direct PostScript) files. EPS is usually the preferred type of file for Adobe Illustrator.