Subsections

• HPGL/1
• HPGL/2
• Controlling Character Size
• Controlling Linewidth
• HP-PCL

Hewlett-Packard HP-GL

Support for HP-GL is provided via two separate drivers; HPGL/1 and HPGL/2. The plotfiles produced by these drivers are ASCII text files which may be edited locally if required, although an editor which can cope sensibly with ASCII escape sequences is required.

HPGL/1

HPGL/1 is basically designed for use with HP compatible pen plotters; it provides no facilities for colour filling polygons. By default, the driver assumes that it is driving an HP7475 plotter with a 6 pen carousel.

Output Medium

Setting the environment variable FV_TRANSP to true will cause the pen velocity to be set to a value suitable for plotting on acetate sheet rather than paper.

Number of Pens

Because the driver assumes that it is dealing with a 6 pen plotter the environment variable FV_NUMPENS must be specified if the actual plotter has a different number of pens. Also, some entry level pen plotters are particularly slow at pen changes, and it is often useful to be able to produce a quick monochrome plot by forcing the driver to use just one pen by setting

   FV_NUMPENS=1

The use of this environment variable should not be confused with the FEMGV command UTILITY SETUP PLOTTER COLOURS n which only indicates to the software the number of colours which are available for colour contour pictures.

Y-Cable Connection

If the plotter is connected to the printer port on a terminal via an HP Y-Cable then setting FV_YCABLE to true will insert the appropriate commands into the plotfile so that automatic switching will be performed.

HPGL/2

HPGL/2 is designed for use with HP compatible raster plotters; this include devices such as inkjet printers and laser printer. Unlike HPGL/1 it does provide facilities for 'colour' filling polygons. This driver would not normally be used with pen plotters.

Mode Switching

 By default, an instruction which will switch the plotter into HPGL/2 mode is placed at the start of the plotfile. This feature enables the plotfile to be sent to a dual mode plotter without the need to manually switch modes.

Because this switching code can cause some DTP packages a certain amount of confusion the resource HPGL2.AutoSwitch can be set to true if the destination device is capable of automatically switching into HPGL/2 mode.

Output Medium

Setting the resource HPGL2.Acetate to true will cause the pen velocity to be set to a value suitable for plotting on acetate sheet rather than paper.

Colour or Monochrome

By default this driver will produce a plotfile for use on colour plotters; the Paintjet for example. If the resource HPGL2.Monochrome is set to true the driver is forced to produce output for monochrome devices such as the LaserJet. Filled polygons will be filled using the output device's built-in greyscales.

There are two resources for controlling the colour setting of the output; HPGL2.Colour and HPGL2.Monochrome. Both of these resources can take the value true or false, so setting HPGL2.Colour to true is the equivalent of setting HPGL2.Monochrome to false, and vice versa.

Page Orientation

The orientation of the plot, landscape or portrait, is controlled by the resource HPGL2.Orientation which can take values of Landscape or Portrait. The default is landscape.

Plot Scaling

The resource HPGL2.PageLayout is used in order to scale the size of the plot. Technically speaking, it is used to determine the HP-GL/2 IR scale command parameters. This command adjusts the P1 and P2 reference points prior to an SC scale command. The default action is to shift P1 up and right by 5 percent, and P2 down and left 10 percent of the page size.

This default scale is represented as,

               Femsys.*.HPGL2.PageLayout : 5,5,90,90

Controlling Character Size

It is possible to scale the size of the characters and marker symbols in an HPGL/2 plotfile using these resources:

Resource Name Default

HPGL2.FontSizeScale 1.0

HPGL2.SmallFontSizeScale 1.0

HPGL2.TitleFontSizeScale Same as FontSizeScale

HPGL2.SymbolScale 1.0

Controlling Linewidth

It is possible to specify the required thickness, in mms, for each of the three linewidths used in an HPGL/2 plotfile using these resources:

Resource Name Default

HPGL2.NormalLineWidth 0.0 (thiness possible)

HPGL2.ThickLineWidth 0.15

HPGL2.ThickestLineWidth 0.35

HP-PCL

HP-PCL was designed mainly for text output, but it also supports the plotting of raster or bitmap images. The FEMGV PAINTJET, LASERJET and DESKJET drivers all use HP-PCL bitmap format. The plotfiles produced by these drivers are in binary format and cannot be edited.

Supported Devices

Computer printer manufacturers seem to announce new models on a weekly basis and therefore this section is far from comprehensive. Currently the FEMGV HP-PCL driver is known to work with the following devices:

• Paintjet
  HP PaintJet and PaintJet XL plotters.
• Deskjet
  HP Deskjet colour plotters; 500C, 550C, 560C, 850C
• Laserjet
  All printers in the HP Laserjet family.

Common Feature

The PAINTJET, LASERJET and DESKJET drivers share a number of common features. The facilities for controlling the behaviour of the driver are explained in the following sections. Please note that resources are described in a generic way, so that Orientation, for example, could be Paintjet.Orientation, Laserjet.Orientation or Deskjet.Orientation. Where a resource applies to a particular device, rather than HP-PCL in general, then the full resource name is given.

• Controlling Page Size and Layout:
  

  The following resources affect the page size and layout:

  Resource Name Default

  PageSize 10x7.5

  PageMargins 0.18+0.27

  PageSizeUnits inch

  Orientation Landscape

  PageSize can be set to a user define size in the form

        WIDTHxHEIGHT
  

  where WIDTH and HEIGHT are in PageSizeUnits units. These can be inch, mm or point. WIDTH refers to the X axis of the plot and HEIGHT refers to the Y axis of the plot.

  PageMargins is used in order to specify the horizontal and vertical offsets, also in PageSizeUnits units. These are measured from the top lefthand corner of the A4 page; for portrait mode plots they indicate the location of the top lefthand corner of the plot and for landscape mode they indicate the location of the top righthand corner.

  Users should be aware that because the software needs to maintain the aspect ratio of the plot, the sizes given via these resources only specify the maximum size of the plot.

  Orientation may be set to Landscape or Portrait, the default being Landscape.

• Plot Resolution:
  Most of the printers are cabable of printing at different resolutions; there is often a trade-off between resolution and number of colours.

  The resource HighRes may be set true in order to force high resolution or the resource LowRes may be set true in order to force low resolution.

  The terms 'high' and 'low' have different meanings to the different plotters:

  • Paintjet: High resolution is 180dpi using 125 dithered colours. Low resolution is 90dpi with 16 solid colours.
  • Deskjet: Although this device is cabable of printing at both 150 and 300dpi, currently only 150dpi is available - again with 125 dithered colours.
  • Laserjet: High resolution is 300dpi with 15 greyscale patterns. Low resolution is 150dpi.
• Plot Quality:
  The resources Quality and Transparency may be use in order to specify the required picture quality.
  • Paintjet:
    The resource Paintjet.Quality may be assigned the value Normal or Presentation.

    When in presentation mode the printer makes multiple printing passes in order to enhance the quality of plot; obviously, this will increase the time taken to print the image. If this resource is unset the plot quality is determined by the keypad settings on the printer.

    Also, when plotting on acetate sheet, the resource Paintjet.Transparency should be given the value true in order to set the printer into transparency mode.

  • Deskjet:
    The resource Deskjet.Quality may be assigned the value Draft or High. If this resource is unset then the graphics quality will be determined by the setting on the printer keypad.

    This driver also offers control for both graphics depletion and graphics shingling. Depletion is a process whereby selected pixels are removed from the graphics image in order to enhance the quality of the picture by reducing the amount of ink used, and therefore the level of saturation. Shingling is a related process where the image is printed in multiple passes in order to give adjacent pixels time to dry, so avoiding colour bleeding. Obviously, the use of shingling will lead to an increase in the time taken to print the image.

    These actions are controlled by the resources Deskjet.Depletion and Deskjet.Shingle

    The exact values which may be assigned to these resources are device dependent, but the following values are generally available:

    Depletion Value Effect

    1 No depletion

    2 25% (Default)

    3 50%

    Shingle Value Degree of Shingling

    0 None

    1 2 pass printing - 50% each pass

    2 4 pass printing - 25% each pass

    Finally, when plotting on acetate sheet, the resource Deskjet.Transparency should be given the value true in order to set the graphics quality, depletion and shingle parameters appropriately.

    You should refer to your Deskjet Users Handbook for a full explanation of this topic.

  • Laserjet :
    These resources are not supported.

• Run length encoded plotfiles:
  By default the driver will attempt to run length encode the plotfiles. This facility can greatly reduce the size of the plotfiles created by the driver, and hence reduce the time taken to send the plotfiles to the printer. Of course, the time taken to create the plotfile is somewhat greater than it would be without this option; setting FV_RASRLE to false will turn this option off.

  Run length encoding is not available with Laserjet printers.

• Customising the Output

  At present, the only customisation available is the ability to scale the size of the FEMGV symbol markers may altered by specifying a scaling factor; SymbolScale.