Print

Prints the image or selected portion of the screen on a laser printer. A laser or inkjet printer that uses a page control language similar to Hewlett-Packard's PCL3 or PCL5, or any PostScript printer supporting PostScript Level 2 or above is required.

Printing Black-and-White or gray scale images

Most laser printers are optimized to print text. Often this results in prints that are too dark. To select a lighter print intensity, select `file...print' from the menu, then click on `Color/Darkness' and adjust the red, green, or blue intensity factors as desired. 128 is normal (dark) printing. Any other values will be multiplied by the data going to the printer to make it lighter or darker. For grayscale images, the red, green, and blue intensity factors will be averaged.

Currently, only laser and inkjet (bubble jet) printers are supported. No support is planned for dot-matrix printers, because the image quality would be unacceptably low.

Print quality can often be improved by using glossy paper sold for pen plotters instead of regular paper.

In addition, some PostScript printers cannot handle images $>$ 8 bits/pixel. In this case, it is necessary to convert the image to 8 bits before printing.

--Column 1--

Vertical/Horizontal - Selects whether image will be printed in ``portrait'' (vertical) or ``landscape'' (horizontal) mode.

Positive/Negative - Print normally (white on the screen = white on the paper) or as a negative.

Print entire image/ print selected area - Select whether to print the entire currently-selected image, or the currently-selected screen area which may span 2 or more images.

Color type

Printer type: PCL / PostScript - Select printer language to use.

--Column 2--

No. of copies - Number of copies of the image to print. Not all printers accept this command.

Printer Device/file name

Color adjustment - Darkness of printed image (255=darkest). The red, green, and blue factors are averaged when color type is ``B/W''.

Vert. offset (inches) - Offsets the image by the specified no. of inches down the page.

Horiz. offset (inches) - Offsets the image by the specified no. of inches to the right across the page.

PCL Printer settings

For PCL printers, such as old HP LaserJets and most inkjet printers, the following options also apply:

Media type - Optimizes the output for the type of paper being used. The following table shows the differences used for different media types on a typical PCL printer:

Media	Print	No. of	Recommended
Type	Quality	passes$^1$	Depletion$^1$
Plain	Draft	1	-
	Normal	2	25% w/gamma
	Presentation	4	50% w/gamma
Bond	Draft	1	-
	Normal	2	25% w/gamma
	Presentation	4	50% w/gamma
Premium	Draft	1	-
	Normal	2	25% w/gamma
	Presentation	4	50% w/gamma
Glossy	Draft	2	25%
	Normal	4	25%
	Presentation	4	0%
Transpar-	Draft	2	25%
ency	Normal	4	25%
	Presentation	4	0%

On certain printers, e.g., H/P 540, the number of passes and the depletion are determined automatically by the printer and may differ from the value in the table. On some other printers, depletion and no. of passes cannot be changed, and setting them to different values has no effect.

$^1$ Recommended by H/P.

Resolution - Selects the desired dots/inch resolution to print the image. Normally this is set to the highest value the printer can handle (see discussion above).

Typical values are:

150 dpi

300 dpi

600 dpi

1200 dpi

This number must be set exactly. For example, a 300 dpi printer may ignore the setting, or it may print nothing at all if the resolution is set at 299 or 301.

Dither size - Determines the number of separate gray or color levels that can be printed:

Dithering	No. of gray/
size	color levels
1x1	2
2x2	4
4x4	16
8x8	64
16x16	256

The size of the printed image also increases proportionately with the dithering size. No ``error propagation'' is performed, in order to maximize resolution for text.

Print Quality: Draft/ Normal/ Presentation - Selects the quality of printout. Presentation quality takes longer, but gives slightly better results.

Not all printers support this option.

Depletion - Improves image quality by removing a certain percentage of the pixels. It is recommended to leave this setting at ``printer default'' unless unsatisfactory results are obtained. The highest two settings also apply gamma correction to the printed image, if this feature is supported by the printer. Gamma correction produces a smoother transition from one color to the next.

See the table above for recommended depletion levels.

Not all printers support this option.

Printer gray balance - If checked, the internal gray balance adjustment in the printer will be activated if present. This is supposed to adjust the colors so that blacks appear black instead of dark green. Do not check this box if you have changed any of the values under ``Printer color adjustment'' (see above), since this would result in correcting the gray balance twice. If the printer does not support this option, checking this will have no effect.

PostScript Printer settings

For PostScript printers, the following additional options apply:

Horizontal image size (inches)

Image ratio (y/x) -

The output will be scaled accordingly to shrink or enlarge the image to the specified size.

Rotation (Degrees) The printout will be rotated counterclockwise by the specified angle. The angle is centered at the lower left corner of the paper. Note that a rotation may cause part of the image to be off the page unless 'horizontal position' is also adjusted. The smallest increment is 0.0001 degree.

Interpolate

If checked, and if the output resolution of the printer is high enough, additional dots will be added to smooth the output.

NOTE: PostScript Level 2 or above is required.

Color printing Color printing uses the same parameters as B/W printing, except it is necessary to select RGB, CMY, or CMYK color instead of grayscale. Color printing can take a much longer time than B/W printing, and requires more printer memory on a laser printer. Use B/W mode whenever possible. The choice between the color types is subjective; however, CMYK generally gives darker blacks.

NOTE: It is not necessary to convert an image to CMYK format to print it in CMYK mode.

Color type - Selects color printing mode.

Grayscale - Recommended for non-color printers and for monochrome images. The pixel values are sent to the printer without filtering them through the colormap. Thus, if the image was made lighter or darker by dragging the colormap palette, these changes will not be reflected in the printout. This setting should not be used for the following types of images:

1. Images that have been converted to a lower bit/pixel depth, e.g. from 24 bits/pixel to 8 bits/pixel.
2. Images containing color.
3. Images such as GIFs which have a discontinuous colormap.

RGB/indexed color Recommended selection for PostScript color printers. Not recommended for PCL inkjet printers, because some PCL printers insist on interpreting this command to mean that all pixels not explicitly defined are to be printed as ``black''. This causes a wide black stripe to be printed next to the image, and causes printing to take a much longer time.

For PostScript printers, this is a good setting to use for both grayscale and 8-bit color images.

If the image is 8 bits, the colors or gray levels are determined by the colormap. If it is a true-color image, the RGB values are used directly.

Prints using red, green, and blue inks if available (not supported by all printers).

CMY color - Recommended selection for PCL color printers. Not recommended for black & white printers.

CMYK color - For color PCL printers - gives darker blacks and brighter colors than CMY but takes 33% longer. For PostScript printers, this option is the same as CMY.

Printer color adjustment - Adjusts each color to to match the printer output with the screen. For each color, a value of 128 (the default) is ``normal''. Increasing the value will increase the intensity of that color. If CMY or CMYK is selected, the cyan, magenta, and yellow inks are changed. If RGB is selected, the red, green, and blue inks are changed. If B/W-grayscale is selected, the black value is taken as the average of the three color values.

NOTE: For CMYK printing, it is important to keep the 3 colors balanced so that the average is 128. Otherwise, the black ink, whose value is derived from the 3 pigments, will also become lighter or darker.

NOTE: Some printers do not handle 24-bit PostScript correctly. If problems occur, convert the image to 8 bits/pixel before printing. (This will also greatly reduce the network load).

Printing to a file or another printer

A 'print file' can be created by entering a filename instead of a printer name under Printer device/file name in the ``Print...'' menu. This will create a print file which can be sent to the printer later, such as at night when it is less busy.

For example, in DOS, printing of a file can be done using the command:

copy /b print.tmp lpt1

However, copy /b does not work correctly on some printers. In this case, try
print.exe , which is a replacement for DOS's print.exe . This program is available at the ftp site. Print.exe is also useful for printing large print files, such as those created by Ghostscript.

In Unix, printing of a file could be done using the command:

lpr -Pmyprinter print.tmp

To schedule the printing at a specific time, use a program such as tnshell in DOS, or cron or at in Unix.

If a printer device is entered, the image will be printed on that device. Printer device refers to the printer name as it is known to the operating system, for example:

DOS version: lpt1 lpt2 prn

Unix version: /dev/lp0 /dev/lp1 /dev/lp2 /dev/printer, etc.

Printing under Unix

The Unix version of imal has the additional options Printer command, printer device, and print to file , for printing to network printers, parallel port printers, or to a file, respectively.

Warning: If the specified ``printer device'' is not a printer or a file, bad things will happen.

In the box ``Printer command'', a command can be entered, such as $\tt lpr -P\rm\it printer \rm\tt -K\rm\it copies\rm$.

Printing in Windows (DOS version only)

In Windows and Windows95, it is possible to print to any network printer provided the printer has been set up correctly with the Print Manager. There are two ways of doing this: ``capturing a printer port'', and directly printing to a Windows-style shared printer name. If the ``Capture Printer Port'' in Windows is clicked, printing to DOS printer devices lpt1 to lpt4 is captured and sent to the specified network address. In this case, ``lpt1'' to ``lpt4'' should be entered. Otherwise, enter a Windows address such as `` $\backslash$ $\backslash$MY_NT_SERVER $\backslash$ITS_PRINTER''. Printer port capture must be ``off'' for the specified printer in order for this to work.