The Format Menu: Hardcopy File Formats

The printing system for Xic and WRspice provides a number of built-in drivers for producing output in various file formats. In Windows, an additional Windows Native driver uses the operating system to provide formatting, thus providing support for any graphical printer known to Windows. The data formats are selected from a drop-down menu available in the Print Control Panel. The name of the currently selected format is displayed on the panel. In Xic only drivers that have been enabled in the technology file are listed (all drivers are enabled by default). The format selections are described below.

Except for the Windows Native driver all formatting is done in the Xic/WRspice printer drivers, and the result is sent to the printer as ``raw'' data. This means that the selected printer must understand the format. In practice, this means that the printer selected must be a PostScript printer, and one of the PostScript formats used, or the printer can be an HP Laserjet, and the PCL format used, etc. The available formats are listed below.

PostScript bitmap
The output is a two-color PostScript bitmap of the plotted area.

PostScript bitmap, encoded
This also produces a two-color PostScript bitmap, but uses compression to reduce file size. Some elderly printers may not support the compression feature.

PostScript bitmap color
This produces a PostScript RGB bitmap of the plotted area. These files can grow quite large, as three bytes per pixel must be stored.

PostScript bitmap color, encoded
This generates a compressed PostScript RGB bitmap of the plotted area. Due to the file size, this format should be used in preference to the non-compressing format, unless the local printer does not support PostScript run length decoding.

PostScript line draw, mono
This driver produces a two-color PostScript graphics list representing the plotted area.

PostScript line draw, color
This produces an RGB color PostScript graphics list representing the plotted area.

HP laser PCL
This driver produces monochrome output suitable for HP and compatible printers. This typically processes more quickly than PostScript on these printers.

HPGL line draw, color
This driver produces output in Hewlett-Packard Graphics Language, suitable for a variety of printers and plotters. In Xic, the fill patterns are defined in the technology file with the HPGLfilled keyword. Other fill pattern definitions are ignored. See the description of the HPGLfilled keyword in the technology file (section A.6) for more information.

Windows Native (Microsoft Windows versions only)
This selection bypasses the drivers in Xic or WRspice and uses the driver supplied by Windows. Thus, any graphics printer supported by Windows should work with this driver.

The Windows Native driver should be used when there is no other choice. If the printer has an oddball or proprietary interface, then the Windows Native driver is the one to use. However, for a PostScript printer, better results will probably be obtained with one of the built-in drivers. The same is true if the printer understands PCL, as do most laser printers. This may vary between printers, so one should experiment and use whatever works best.

In the Unix/Linux versions, selecting a page size from the Media menu will load that size into the entry areas that control printed image size. This is the only effect, and there is no communication of actual page size to the printer. This is true as well under Windows, except in the Windows Native driver. Microsoft's driver will clip the image to the page size before sending it to the printer, and will send a message to the printer giving the selected paper size. The printer may not print if the given paper size is not what is in the machine. Thus, when using this driver, it is necessary to select the actual paper size in use.

Xfig line draw, color
Xfig is a free (and very nice) drafting program available over the internet. Through the transfig program, which should be available from the same source, output can be further converted to a dozen or so different formats. In Xic, the fill patterns are defined in the technology file with the XfigFilled keyword. Other fill pattern definitions are ignored. See the description of the XfigFilled keyword in the technology file (section A.6) for more information.

Image: jpeg, tiff, png, etc.
This driver converts into a multitude of bitmap file formats. This supports file generation only. The type of file is determined by the extension of the file name provided (the file name should have one!). The driver can convert to several formats internally, and can convert to many more by making use of ``helper'' programs that may be on your system.

Internal formats
Extension	Format
ppm, pnm, pgm	portable bitmap (netpbm)
ps	PostScript
jpg, jpeg	JPEG
png	PNG
tif, tiff	TIFF

For the bitmap image formats, the driver resolution choice really doesn't change image resolution, but changes the size of the image bitmap in pixels. The image ``resolution'' is the number of pixels per inch in the image size entries. Thus, selecting a 4x4 inch image with resolution 100 would create a 400x400 pixel image. Note that selecting resolution 200 and size 4x4 would produce the same bitmap size as 100 and 8x8.

Under Microsoft Windows, an additional feature is available. If the word ``clipboard'' is entered in the File Name text box, the image will be composed in the Windows clipboard, from where it can be pasted into other Windows applications. There is no file generated in this case.

On Unix/Linux systems, if you have the open-source ImageMagick or netpbm packages installed then many more formats are available, including GIF and PDF. These programs are standard on most Linux distributions. The imsave system, which is used to implement this driver and otherwise generate image files, employs a special search path to find helper functions (convert from ImageMagick, the netpbm functions, cjpeg and djpeg). The search path (a colon-delimited list of directories) can be provided in the environment variable IMSAVE_PATH. If not set, the internal path is ``/usr/bin:/usr/local/bin:/usr/X11R6/bin''. The helper function capability is not available under Microsoft Windows.

If the Legend button is active, the image will contain the legend. If Landscape is selected, the image will be rotated 90 degrees.

The choice between PostScript line draw and bitmap formats is somewhat arbitrary. Although the data format is radically different, the plots should look substantially the same. A bitmap format typically takes about the same amount of time to process, independent of the data shown, whereas a line draw format takes longer with more objects to render. For very simple layouts and all schematics and WRspice plots, the line draw formats are the better choice, but for most layouts the bitmap format will be more efficient.

The necessary preamble for Encapsulated PostScript (EPSF-3.0) is included in all PostScript files, so that they may be included in other documents without modification.