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Printing Graphics

Printing Graphics. An introduction to capabilities of the HP Printer Control Language. Escape-sequences. The PCL language employs some special sequences of ASCII control-codes, known as ‘escape’ sequences (since they begin with the code for the escape-key: 0x1B)

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Printing Graphics

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  1. Printing Graphics An introduction to capabilities of the HP Printer Control Language

  2. Escape-sequences • The PCL language employs some special sequences of ASCII control-codes, known as ‘escape’ sequences (since they begin with the code for the escape-key: 0x1B) • The character-sequence ‘\e’ may be used to generate this special non-printable byte • The punctuation-symbols, numerals, and alphabetic characters that follow specify a specific command to the HP laser printer

  3. Printer Communication • An application that wishes to do printing can create a textfile containing a mixture of document text and PCL commands • This text file is then ‘submitted’ to the printer using a Linux command (e.g., ‘lpr’) • The printer recognizes commands by the occurrence of an ‘escape’ code

  4. Initilization • Printer initialization command has format: ESC E • Example: fprintf( prn, “\eE” ); // This statement writes the initialization // command to a file whose file-pointer is // the ‘prn’ variable

  5. Dots-per-inch • Setting print resolution for raster graphics is done with the following command: ESC * t # R • Here the ‘#’ symbol denotes a numeric parameter that specifies the number of dots-per-inch (i.e., the pixel resolution) • Possible choices are: 75, 100, 150, 300

  6. Set the Cursor Position • Set the cursor’s Y-coordinate: ESC * p # Y • Set the cursor’s X-coordinate: ESC * p # X • Example: If dots-per-inch equals 300, then fprintf( prn, “\e*p%dY\e*p%dX”, 150, 150 ); places the cursor a half-inch from margins

  7. Set the Compression Mode • Here is the command that specifies the type of raster data-compression used: ESC * b # M • The possible numeric parameters are: • 0: unencoded (no compression) • 1: run-length encoding • 2: tagged image file format (TIFF) • 3: delta row compression

  8. Enter Raster Graphics Mode • The printer’s default mode is ‘text’ mode • To switch into raster graphics mode, the following command is issued: ESC * r # A • Here the ‘#’ symbol specifies the type of cursor-positioning that is used: • 1 means use current cursor position • 0 means use the printer’s left margin

  9. Sending Raster Data • Here is the command for sending raster graphics data to the printer: ESC * b # W • Here the ‘#’ symbol stands for a numeric parameter that specifies the number of bytes of raster data that follows the ‘W’ • Then the cursor moves to the next row

  10. Leaving Raster Graphics Mode • To exit from raster graphics mode, the following command is used: ESC * r B • This command switches the printer back to its normal ‘text’ mode, and it is issued after the final row of raster graphics data is sent

  11. End-of-Page • The PCL language is ‘page oriented’, and once a page’s description is complete, the printer should eject that page • The ‘form-feed’ command ‘\f’ can be sent to the printer to eject the completed page: fprintf( prn, “\f” );

  12. Our ‘wavprint.cpp’ demo • We have posted an application program that prints certain Waveform Audio files, using the printer’s PCL raster graphics commands • So far it only works with 8-bit non-stereo data-format • To avoid wasting paper and toner, it only prints the first page of the waveform

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