16 Printing Graphics

This chapter describes the control functions you use to format and print graphics on a local printer connected to the VT300. You can also print graphics directly from the terminal, by pressing Shift-Local Print. See Chapter 11 of Installing and Using the VT330/VT340 Video Terminal.

Selecting a Format for Printing

This section describes the control functions you use to format graphics before printing them from the screen. These control functions affect print screen commands. If you do not have a printer connected to the terminal, the terminal ignores these functions.

Graphics Expanded Print Mode (DECGEPM)

This control function selects whether the terminal sends a compressed or expanded graphics image to the printer. The compressed image fits on A4 or 8½ inch wide paper. The expanded image fits on 13 inch wide paper.

Default: Compressed

Graphics Print Color Mode (DECGPCM)

This control function selects whether the terminal sends a color or black and white image to the printer. You should only use the color setting with the VT340.

Default: Black and white

Graphics Print Color Syntax (DECGPCS)

This control function selects which color coordinate system the terminal uses in print color mode (DECGPCM). You should only use this function with a VT340.

You can select one of two universal color coordinate systems, HLS (hue, lightness, and saturation) or RGB (red, green, and blue).

Default: HLS

Graphics Print Background Mode (DECGPBM)

This control function selects whether the terminal sends the background area to the printer during a graphics print screen operation. This control function only works when print color mode (DECGPCM) is set (color).

Default: No background

Graphics Rotated Print Mode (DECGRPM)

This control function selects whether the terminal sends a compressed or rotated graphics image to the printer.

Sending Graphics to the Host or Printer

This section describes the control functions you use to send graphics to the host or a local printer.

Graphics to Host (MC)

This control function causes ReGIS hard copy commands to send screen images to the active host session. See Part 1 of this volume for details on ReGIS. The terminal ignores this function if the printer is assigned to the inactive session. See Volume 1, Chapter 14 of this manual for details on session management.

After receiving this command, the terminal sends the complete graphics bitmap to the host.

Graphics to Printer (MC)

This control function causes ReGIS hard copy commands to send screen images to the printer. See Part 1 of this volume for details on ReGIS. The printer prints the ReGIS images as they appear on the screen. You can use either of the following sequences.

After receiving this command, the terminal sends the complete graphics bitmap to the printer.

Sixel Graphics Levels – Matching Your Printer

Different printers produce different output quality. This section describes the sixel graphics levels you can use to match the capabilities of the printer connected to your terminal.

A sixel is a group of six pixels in a vertical column. A pixel is the smallest displayable unit on the screen. A sixel is represented by 6 bits in a character code. Each pixel in the sixel corresponds to each bit in the character code. A value of 1 for a bit indicates that a pixel is on, a 0 value indicates a pixel is off. Chapter 14 describes sixel graphics in detail.

Sixel printing is the printing of each defined sixel in left-to-right, top-to-bottom order.

There are two ways to send sixel information to a local printer, press Local Print or send a media copy command.

• Local Print Key
  When you press Local Print, the VT300 sends a carriage return (CR) to the printer to reset the printing position to the left margin. Then the terminal sends the sixel device control string.

• Media Copy Command
  When an application sends a media copy command to the VT300 (such as Graphics to Printer), the terminal does not send a carriage return to the printer. The terminal sends only the sixel device control string. Omitting the carriage return lets the application initialize the starting sixel position.

The VT300 supports different levels of the sixel graphics protocol to match the capabilities of the local printer used. The user can select the sixel graphics level from the Printer Set-Up screen.

The sixel graphics level determines how the terminal matches the printer's aspect ratio, horizontal grid size, background printing, and color printing capabilities. The VT300 has a pixel aspect ratio of 1 to 1.

Level 1 Sixel Devices

Level 1 sixel devices do not support the following sixel protocol commands.

• Set raster attributes
• Background select
• Horizontal grid size
• Macro parameter

Level 1 devices have a fixed aspect ratio of 2 to 1 (2 horizontal pixels to 1 vertical pixel), and a horizontal grid size of approximately 188 × 0.025 mm (7.5 × 0.001 in). Level 1 is the factory-default for the VT300.

At level 1, the terminal always sends sixel device control strings to the printer in a 7-bit format as follow.

ESC P 1 q S...S ESC \

where

S...S is the sixel data defining the image.

A typical level 1 device is Digital's LA50 printer.

Level 2 Sixel Devices

Level 2 sixel devices support the following sixel protocol commands.

• Set raster attributes
• Background select
• Horizontal grid size
• Macro parameter

At level 2, the VT300 sends sixel data to the printer in the following format.

ESC P Pn1; Pn2; Pn3; q " Pn4; Pn5; Pn6; Pn7 S...S ESC \

where

Typical level 2 printers are Digital's LA75 and LN03 printers.

NOTE: You must use level 1 to print expanded or rotated images on an LA75. This selection compensates for firmware differences between the printer and terminal.

LA210 Printer

Digital's LA210 printer is a special case. The LA210 is similar to a level 2 device, but does not recognize the set raster attributes command. At the LA210 level, the VT300 uses macro parameter 9 to specify a 1 to 1 aspect ratio with a grid size of 338 × 0.025 mm (13.5 × 0.001 in).

For compressed print operations, the VT300 uses the same sixel device control string format as in level 1.

For expanded and rotated print operations, the VT300 uses the following sixel device control string format.

ESC P 9 q S...S ESC \

where

Program Example for Printing a ReGIS Image on the LN03

The following program prints an expanded ReGIS image on an LN03 laser printer. To print an expanded ReGIS image from your VT300 terminal to a local LN03 printer, perform the following steps.

1. In the Printer Set-Up screen, set the Sixel Print Option feature to "expanded".

2. Use the following escape sequences in your program (ESC = escape character).

ReGIS display addressing command sets the terminal to full screen addressing. ReGIS hard copy command sends the image to the printer.

ESCPp S(A[0,0][799,499]H) ESC\

For more information, see Chapter 2.

Summary

Table 16-1 is a summary of the graphics printing control sequences in this chapter.