Printing Images from MicroStation V8 Raster Manager.

 Applies To 
 Environment: N/A
 Area: Printing
 Original Author:Gary Williams, Bentley Technical Support Group









Printing Images

Raster Manager is an application within MicroStation V8 that allows you to reference (display and control) raster images. These images can be printed with a raster device. Raster Manager supports Postscript, HPGL2/RTL, and all raster devices supported through the Windows print manager.

Typically, users may have aerial photos as a raster image background-either a single image or multiple images (a mosaic) with vector line work laid over top. The images may be color, greyscale, or black and white, and may have similar or different pixel resolutions.

Figure 1
You can produce hybrid prints from Raster Manager by simply choosing "Print" from the main MicroStation V8 File menu.
To print, you need to select a suitable Bentley print driver configuration file (*.plt), or to access the Windows printer drivers use "printer.plt." These files contain all the required controls to print raster images.

The table in Figure 2 is a guide to choosing the correct printer driver file.

Note: To print the images, Raster Manager's print toggle must be ON (which is the default). This toggle enables or disables the printing of Type 90 raster images, which is type supported by Raster Manager. It has no effect on the printing of Type 87/88 rasters. You can find the toggle in both of the following menus:

Figure 2
Raster Manager dialog box (expanded dialog)
Attachment Settings dialog box > Display/Print tab
The output resolution of the images is very important. Set it too low and the images may appear very pixelated. Set it too high and the print files may become too large to handle and print. It is recommended that you select the maximum possible number of pixels per inch for the output resolution. You can use a lower resolution to obtain a quick draft output, but the higher resolution should be used to obtain high quality output.

To set the resolution, open the driver file for editing from the print dialog box (File > Edit Printer Driver) and set the PIXEL_RESOLUTION record value to the desired resolution. The range of values spans from 1 to 300 dpi. The default is 75 dpi. Save and exit, then reload the driver file to make the setting active (File > Reload Printer Driver).

To ensure maximum quality for your print, you should set this value to the same resolution as that of your printing device. With devices that use half-toning, however, the maximum resolution that you can achieve equals the net resolution after half-toning (that is, the net resolution will be less that the overall resolution of the device). Since a value set higher than necessary usually does not provide added resolution, it is advisable to determine the optimum value to minimize the size of your print file.

To calculate the output resolution that will produce the smallest print file size, you need to determine the net resolution of your device. This value should be less than the resolution of the printer. The Raster Manager default value is 75, since it is the typical net resolution for 300 dpi printers that print in grayscale with half-toning. To optimize your print file size, you can use the following formula:

(Image Width/Pixel Size) / Width of print = Optimal Resolution.

As image resolution is measured in dpi (dots per inch) it is generally easier to use imperial measurements when determining this value. The pixel size for each image can be found in the Raster Manager dialog box.

For example, if the image width is 1000 feet, the pixel size is one foot and the width of the print is five inches, then:

(1000/1) / 5 = 200 dpi

It is also possible to use this formula in reverse to work out the optimal pixel size. Having an image of a greater resolution than the device can print may well be a waste of resources.

150 dpi = (1000/p) / 8

Hence the optimal pixel size "p" would be 0.833

Figure 3
Printing images from Raster Manager is similar to standard printing, except that only particular printer driver files can be used, as mentioned above. The other steps are the same.
From the MicroStation File menu, select Print. The Print dialog box opens.

From the Print dialog box, in the Printer and Paper Size field, choose one of the following:

Windows Printer - output is sent directly to the Windows system printer
Bentley Driver - if this option is chosen, select a suitable Bentley driver
In the Print dialog box, click the Print icon or choose Print from the Print dialog box's File menu.

If you are outputting to the Windows printer or are using Raster Image Processor (RIP) drivers, and you select Print, the image file is processed and then printed.

If you are outputting via a Bentley print driver, the "Save Print As" dialog box will open. You choose the name and location for the output print file and save it to disk. To print the saved print file, open an MS-DOS window, change the directory to point to where the print file is located, and use the key-in:


where is the name of the print file and is the port to which the printer is attached (such as lpt1:). Printing begins when the printer receives the whole of the print file.

The following are mandatory records for printing raster files. They are found in the .plt files that allow printing of raster images.

Specifies the printing resolution for Raster files (see above).

Enables/Disables grayscale printing of raster files. 1=On, 0=Off, Default=0.

Used to specify the background color of monochrome rasters in Raster Manager. If BACKGROUND =0 or 1 (white or black), the foreground is inverted if identical to the MSv8 background. If BACKGROUND=2 (color), no changes are brought to the monochrome raster. Default=0.

Defines the percentage of contrast applied to the image being printed. Default=50.

Defines the percentage of brightness applied to the image being printed. Default=50.

Enables/disables printing of raster images. 1=Don't Plot, 0=Plot, Default=0.

Enables/disables Plot on the Fly printing of raster files. 1=On, 0=Off, Default=0.

This setting may be used when large print files exceed the memory of the printer. It may happen that the raster portion of the print does not fit entirely into the printer's memory and hence will not print or will only print part of the image. When this happens there are several options available:

Add more memory to the printer
Reduce the size of the print file by reducing the resolution or paper size
Use the Plot-On-the-Fly feature


Figure 4
The Plot-On-The-Fly feature is activated by setting the record in the .plt file to "1." MicroStation then generates the print one strip (band) at a time. This method is slower but allows printing large raster files on a printer with minimal memory installed. For this to work, the entire design file (not including the rasters) must fit into the printer's memory. Conventional ways require that the raster data be spooled first and then the vector data (design file). When using Plot On The Fly, the vector data is spooled first. One thing to note when using Plot On The Fly, it always produces translucent vectors, i.e. Vector information will be transparent and some colors, like yellow, may not show properly over image backgrounds.