harvey/sys/src/cmd/gs/src/gdevstc3.c

/* Copyright (C) 1995, 1996 Aladdin Enterprises.  All rights reserved.
  
  This software is provided AS-IS with no warranty, either express or
  implied.
  
  This software is distributed under license and may not be copied,
  modified or distributed except as expressly authorized under the terms
  of the license contained in the file LICENSE in this distribution.
  
  For more information about licensing, please refer to
  http://www.ghostscript.com/licensing/. For information on
  commercial licensing, go to http://www.artifex.com/licensing/ or
  contact Artifex Software, Inc., 101 Lucas Valley Road #110,
  San Rafael, CA  94903, U.S.A., +1(415)492-9861.
*/

/* $Id: gdevstc3.c,v 1.4 2002/02/21 22:24:52 giles Exp $*/
/* Epson Stylus-Color Printer-Driver */

/***
     This file holds the sample-implementation of a RGB-algorithm for
     the stcolor-driver. It is available via

          gs -sDEVICE=stcolor -sDithering=gsrgb ...

     Actually this is no dithering-algorithm, it lets ghostscript do the job.
     This achieved, by requesting BYTE-Values between 0 and 1 to be delivered,
     which causes a depth of 1-Bit by default.

 ***/

/*
 * gdevstc.h holds all the includes and the driver-specific definitions, so
 * it is the only include you need. To add a new algorthim, STC_MODI in
 * gdevstc.h should be extended. (see the instructions there)
 */

#include "gdevstc.h"

/*
 * the routine required.
 */

/*ARGSUSED*/
int 
stc_gsrgb(stcolor_device *sdev,int npixel,byte *ip,byte *buf,byte *out)
{

   int   error = 0;

/*
 * There are basically 3 Types of calls:
 * npixel < 0    => initialize buf, if this is required
 *                  (happens only if requested)
 * npixel > 0    => process next scanline, if the flag STC_WHITE is set, then
 *                  in == NULL signals, that the basic-driver has decided
 *                  that this scanline is white. (Useful for really dithering
 *                  drivers)
 */

/* ============================================================= */
   if(npixel > 0) {  /* npixel >  0 -> scanline-processing       */
/* ============================================================= */

      int p;

/*
 *    simply merge the color-values into a single byte 
 *    (RED, GREEN, BLUE are defined in gdevstc.h)
 */
      for(p = 0; p < npixel; ++p,++out) { /* loop over pixels */

         *out = 0;
         if(*ip++) *out |= RED;
         if(*ip++) *out |= GREEN;
         if(*ip++) *out |= BLUE;

      }                                   /* loop over pixels */

/* ============================================================= */
   } else {          /* npixel <= 0 -> initialisation            */
/* ============================================================= */
/*
 * besides buffer-Initialisation, one may check the parameters in
 * the algorithm-table of the driver.
 */

/*    we didn't check for the white-calls above, so they would cause errors */
      if(sdev->stc.dither->flags & STC_WHITE)              error = -1;

/*    if we're not setup for bytes, this is an error too */
      if((sdev->stc.dither->flags & STC_TYPE) != STC_BYTE) error = -2;

/*    and rgb-mode is the only supported mode */
      if(sdev->color_info.num_components != 3)             error = -3;

/*    we can't deal with ghostscript-data directly. */
      if(sdev->stc.dither->flags & STC_DIRECT)             error = -4;

/* ============================================================= */
   } /* scanline-processing or initialisation */
/* ============================================================= */

   return error;
}