/*
 * TWAIN Plug-in
 * Copyright (C) 1999 Craig Setera
 * Craig Setera <setera@home.com>
 * 03/31/1999
 *
 * Updated for Mac OS X support
 * Brion Vibber <brion@pobox.com>
 * 07/22/2004
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 *
 * Based on (at least) the following plug-ins:
 * Screenshot
 * GIF
 * Randomize
 *
 * Any suggestions, bug-reports or patches are welcome.
 *
 * This plug-in interfaces to the TWAIN support library in order
 * to capture images from TWAIN devices directly into GIMP images.
 * The plug-in is capable of acquiring the following type of
 * images:
 * - B/W (1 bit images translated to grayscale B/W)
 * - Grayscale up to 16 bits per pixel
 * - RGB up to 16 bits per sample (24, 30, 36, etc.)
 * - Paletted images (both Gray and RGB)
 *
 * Prerequisites:
 * Should compile and run on both Win32 and Mac OS X 10.3 (possibly
 * also on 10.2).
 *
 * Known problems:
 * - Multiple image transfers will hang the plug-in.  The current
 *   configuration compiles with a maximum of single image transfers.
 * - On Mac OS X, canceling doesn't always close things out fully.
 * - Epson TWAIN driver on Mac OS X crashes the plugin when scanning.
 */

/*
 * Revision history
 *  (02/07/99)  v0.1   First working version (internal)
 *  (02/09/99)  v0.2   First release to anyone other than myself
 *  (02/15/99)  v0.3   Added image dump and read support for debugging
 *  (03/31/99)  v0.5   Added support for multi-byte samples and paletted
 *                     images.
 *  (07/23/04)  v0.6   Added Mac OS X support.
 */
#include "config.h"

#include <glib.h>		/* Needed when compiling with gcc */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "tw_platform.h"
#include "tw_local.h"

#include "libgimp/gimp.h"
#include "libgimp/stdplugins-intl.h"

#include "tw_func.h"
#include "tw_util.h"

#ifdef _DEBUG
#include "tw_dump.h"
#endif /* _DEBUG */

/*
 * Plug-in Definitions
 */
#define PLUG_IN_NAME        "twain-acquire"
#define PLUG_IN_DESCRIPTION "Capture an image from a TWAIN datasource"
#define PLUG_IN_HELP        "This plug-in will capture an image from a TWAIN datasource"
#define PLUG_IN_AUTHOR      "Craig Setera (setera@home.com)"
#define PLUG_IN_COPYRIGHT   "Craig Setera"
#define PLUG_IN_VERSION     "v0.6 (07/22/2004)"

#ifdef _DEBUG
#define PLUG_IN_D_NAME      "twain-acquire-dump"
#define PLUG_IN_R_NAME      "twain-acquire-read"
#endif /* _DEBUG */

/*
 * Application definitions
 */
#define MAX_IMAGES 1

/*
 * Definition of the run states
 */
#define RUN_STANDARD 0
#define RUN_DUMP 1
#define RUN_READDUMP 2

/* Global variables */
pTW_SESSION twSession = NULL;

static char        *destBuf = NULL;
#ifdef _DEBUG
static int         twain_run_mode = RUN_STANDARD;
#endif

/* Forward declarations */
void preTransferCallback(void *);
int  beginTransferCallback(pTW_IMAGEINFO, void *);
int  dataTransferCallback(pTW_IMAGEINFO, pTW_IMAGEMEMXFER, void *);
int  endTransferCallback(int, int, void *);
void postTransferCallback(int, void *);

static void query (void);
static void run   (const gchar      *name,
		   gint              nparams,
		   const GimpParam  *param,
		   gint             *nreturn_vals,
		   GimpParam       **return_vals);

/* This plug-in's functions */
GimpPlugInInfo PLUG_IN_INFO =
{
  NULL,    /* init_proc */
  NULL,    /* quit_proc */
  query,   /* query_proc */
  run,     /* run_proc */
};

extern void set_gimp_PLUG_IN_INFO_PTR(GimpPlugInInfo *);

/* Data structure holding data between runs */
/* Currently unused... Eventually may be used
 * to track dialog data.
 */
typedef struct {
  gchar  sourceName[34];
  gfloat xResolution;
  gfloat yResolution;
  gint   xOffset;
  gint   yOffset;
  gint   width;
  gint   height;
  gint   imageType;
} TwainValues;

/* Default Twain values */
static TwainValues twainvals =
{
  "",
  100.0, 100.0,
  0, 0,
  0, 0,
  TWPT_RGB
};

/* The standard callback functions */
TXFR_CB_FUNCS standardCbFuncs = {
  preTransferCallback,
  beginTransferCallback,
  dataTransferCallback,
  endTransferCallback,
  postTransferCallback };

/******************************************************************
 * Dump handling
 ******************************************************************/

#ifdef _DEBUG
/* The dumper callback functions */
TXFR_CB_FUNCS dumperCbFuncs = {
  dumpPreTransferCallback,
  dumpBeginTransferCallback,
  dumpDataTransferCallback,
  dumpEndTransferCallback,
  dumpPostTransferCallback };

void
setRunMode(char *argv[])
{
  char *exeName = strrchr(argv[0], '\\') + 1;

  LogMessage("Executable name: %s\n", exeName);

  if (!_stricmp(exeName, DUMP_NAME))
    twain_run_mode = RUN_DUMP;

  if (!_stricmp(exeName, RUNDUMP_NAME))
    twain_run_mode = RUN_READDUMP;
}
#endif /* _DEBUG */

#ifndef TWAIN_ALTERNATE_MAIN
MAIN()
#endif

int
scanImage (void)
{
#ifdef _DEBUG
  if (twain_run_mode == RUN_READDUMP)
    return readDumpedImage (twSession);
  else
#endif /* _DEBUG */
    return getImage (twSession);
}

/*
 * initTwainAppIdentity
 *
 * Initialize and return our application's identity for
 * the TWAIN runtime.
 */
static pTW_IDENTITY
getAppIdentity(void)
{
  pTW_IDENTITY appIdentity = g_new (TW_IDENTITY, 1);

  /* Set up the application identity */
  appIdentity->Id = 0;
  appIdentity->Version.MajorNum = 0;
  appIdentity->Version.MinorNum = 1;
  appIdentity->Version.Language = TWLG_USA;
  appIdentity->Version.Country = TWCY_USA;
  strcpy(appIdentity->Version.Info, "GIMP TWAIN 0.6");
  appIdentity->ProtocolMajor = TWON_PROTOCOLMAJOR;
  appIdentity->ProtocolMinor = TWON_PROTOCOLMINOR;
  appIdentity->SupportedGroups = DG_IMAGE;
  strcpy(appIdentity->Manufacturer, "Craig Setera");
  strcpy(appIdentity->ProductFamily, "GIMP");
  strcpy(appIdentity->ProductName, "GIMP");

  return appIdentity;
}

/*
 * initializeTwain
 *
 * Do the necessary TWAIN initialization.  This sets up
 * our TWAIN session information.  The session stuff is
 * something built by me on top of the standard TWAIN
 * datasource manager calls.
 */
pTW_SESSION
initializeTwain(void)
{
  pTW_IDENTITY appIdentity;

  /* Get our application's identity */
  appIdentity = getAppIdentity();

  /* Create a new session object */
  twSession = newSession(appIdentity);

  /* Register our image transfer callback functions */
#ifdef _DEBUG
  if (twain_run_mode == RUN_DUMP)
    registerTransferCallbacks(twSession, &dumperCbFuncs, NULL);
  else
#endif /* _DEBUG */
    registerTransferCallbacks(twSession, &standardCbFuncs, NULL);
  return twSession;
}

/******************************************************************
 * GIMP Plug-in entry points
 ******************************************************************/

/*
 * Plug-in Parameter definitions
 */
#define NUMBER_IN_ARGS 1
#define IN_ARGS { GIMP_PDB_INT32, "run_mode", "Interactive, non-interactive" }
#define NUMBER_OUT_ARGS 2
#define OUT_ARGS \
	{ GIMP_PDB_INT32, "image_count", "Number of acquired images" }, \
	{ GIMP_PDB_INT32ARRAY, "image_ids", "Array of acquired image identifiers" }


/*
 * query
 *
 * The plug-in is being queried.  Install our procedure for
 * acquiring.
 */
static void
query (void)
{
  static GimpParamDef args[] = { IN_ARGS };
  static GimpParamDef return_vals[] = { OUT_ARGS };

#ifdef _DEBUG
  if (twain_run_mode == RUN_DUMP)
    {
      /* the installation of the plugin */
      gimp_install_procedure(PLUG_IN_D_NAME,
                             PLUG_IN_DESCRIPTION,
                             PLUG_IN_HELP,
                             PLUG_IN_AUTHOR,
                             PLUG_IN_COPYRIGHT,
                             PLUG_IN_VERSION,
                             N_("TWAIN (Dump)..."),
                             NULL,
                             GIMP_PLUGIN,
                             NUMBER_IN_ARGS,
                             NUMBER_OUT_ARGS,
                             args,
                             return_vals);

      gimp_plugin_menu_register (PLUG_IN_D_NAME, "<Toolbox>/File/Acquire");
    }
  else if (twain_run_mode == RUN_READDUMP)
    {
      /* the installation of the plugin */
      gimp_install_procedure(PLUG_IN_R_NAME,
                             PLUG_IN_DESCRIPTION,
                             PLUG_IN_HELP,
                             PLUG_IN_AUTHOR,
                             PLUG_IN_COPYRIGHT,
                             PLUG_IN_VERSION,
                             N_("TWAIN (Read)..."),
                             NULL,
                             GIMP_PLUGIN,
                             NUMBER_IN_ARGS,
                             NUMBER_OUT_ARGS,
                             args,
                             return_vals);

      gimp_plugin_menu_register (PLUG_IN_R_NAME, "<Toolbox>/File/Acquire");
    }
  else
#endif /* _DEBUG */
    {
      /* the installation of the plugin */
      gimp_install_procedure(PLUG_IN_NAME,
                             PLUG_IN_DESCRIPTION,
                             PLUG_IN_HELP,
                             PLUG_IN_AUTHOR,
                             PLUG_IN_COPYRIGHT,
                             PLUG_IN_VERSION,
                             N_("_TWAIN..."),
                             NULL,
                             GIMP_PLUGIN,
                             NUMBER_IN_ARGS,
                             NUMBER_OUT_ARGS,
                             args,
                             return_vals);

      gimp_plugin_menu_register (PLUG_IN_NAME, "<Toolbox>/File/Acquire");
    }
}


/* Return values storage */
static GimpParam values[3];

/*
 * run
 *
 * The plug-in is being requested to run.
 * Capture an image from a TWAIN datasource
 */
static void
run (const gchar      *name,
     gint              nparams,
     const GimpParam  *param,
     gint             *nreturn_vals,
     GimpParam       **return_vals)
{
  GimpRunMode run_mode;

  /* Initialize the return values
   * Always return at least the status to the caller.
   */
  values[0].type = GIMP_PDB_STATUS;
  values[0].data.d_status = GIMP_PDB_SUCCESS;
  *nreturn_vals = 1;
  *return_vals = values;

  INIT_I18N ();

  /* Before we get any further, verify that we have
   * TWAIN and that there is actually a datasource
   * to be used in doing the acquire.
   */
  if (!twainIsAvailable()) {
    values[0].data.d_status = GIMP_PDB_EXECUTION_ERROR;
    return;
  }

  /* Get the runmode from the in-parameters */
  run_mode = param[0].data.d_int32;

  /* Set up the rest of the return parameters */
  values[1].type = GIMP_PDB_INT32;
  values[1].data.d_int32 = 0;
  values[2].type = GIMP_PDB_INT32ARRAY;
  values[2].data.d_int32array = g_new (gint32, MAX_IMAGES);

  /* How are we running today? */
  switch (run_mode) {
  case GIMP_RUN_INTERACTIVE:
    /* Retrieve values from the last run...
     * Currently ignored
     */
    gimp_get_data(PLUG_IN_NAME, &twainvals);
    break;

  case GIMP_RUN_NONINTERACTIVE:
    /* Currently, we don't do non-interactive calls.
     * Bail if someone tries to call us non-interactively
     */
    values[0].data.d_status = GIMP_PDB_CALLING_ERROR;
    return;

  case GIMP_RUN_WITH_LAST_VALS:
    /* Retrieve values from the last run...
     * Currently ignored
     */
    gimp_get_data(PLUG_IN_NAME, &twainvals);
    break;

  default:
    break;
  } /* switch */

  /* Have we succeeded so far? */
  if (values[0].data.d_status == GIMP_PDB_SUCCESS)
    twainMain ();

  /* Check to make sure we got at least one valid
   * image.
   */
  if (values[1].data.d_int32 > 0) {
    /* An image was captured from the TWAIN
     * datasource.  Do final Interactive
     * steps.
     */
    if (run_mode == GIMP_RUN_INTERACTIVE) {
      /* Store variable states for next run */
      gimp_set_data(PLUG_IN_NAME, &twainvals, sizeof (TwainValues));
    }

    /* Set return values */
    *nreturn_vals = 3;
  } else {
    values[0].data.d_status = GIMP_PDB_EXECUTION_ERROR;
  }
}

/***********************************************************************
 * Image transfer callback functions
 ***********************************************************************/

/* Data used to carry data between each of
 * the callback function calls.
 */
typedef struct {
  gint32 image_id;
  gint32 layer_id;
  GimpPixelRgn pixel_rgn;
  GimpDrawable *drawable;
  pTW_PALETTE8 paletteData;
  int totalPixels;
  int completedPixels;
} ClientDataStruct, *pClientDataStruct;

/*
 * preTransferCallback
 *
 * This callback function is called before any images
 * are transferred.  Set up the one time only stuff.
 */
void
preTransferCallback(void *clientData)
{
  /* Initialize our progress dialog */
  gimp_progress_init(_("Transferring TWAIN data..."));
}

/*
 * beginTransferCallback
 *
 * The following function is called at the beginning
 * of each image transfer.
 */
int
beginTransferCallback(pTW_IMAGEINFO imageInfo, void *clientData)
{
  int imageType, layerType;

  pClientDataStruct theClientData = g_new (ClientDataStruct, 1);

#ifdef _DEBUG
  logBegin(imageInfo, clientData);
#endif

  /* Decide on the image type */
  switch (imageInfo->PixelType) {
  case TWPT_BW:
  case TWPT_GRAY:
    /* Set up the image and layer types */
    imageType = GIMP_GRAY;
    layerType = GIMP_GRAY_IMAGE;
    break;

  case TWPT_RGB:
    /* Set up the image and layer types */
    imageType = GIMP_RGB;
    layerType = GIMP_RGB_IMAGE;
    break;

  case TWPT_PALETTE:
    /* Get the palette data */
    theClientData->paletteData = g_new (TW_PALETTE8, 1);
    twSession->twRC = callDSM(APP_IDENTITY(twSession), DS_IDENTITY(twSession),
			      DG_IMAGE, DAT_PALETTE8, MSG_GET,
			      (TW_MEMREF) theClientData->paletteData);
    if (twSession->twRC != TWRC_SUCCESS)
      return FALSE;

    switch (theClientData->paletteData->PaletteType) {
    case TWPA_RGB:
      /* Set up the image and layer types */
      imageType = GIMP_RGB;
      layerType = GIMP_RGB_IMAGE;
      break;

    case TWPA_GRAY:
      /* Set up the image and layer types */
      imageType = GIMP_GRAY;
      layerType = GIMP_GRAY_IMAGE;
      break;

    default:
      return FALSE;
    }
    break;

  default:
    /* We don't know how to deal with anything other than
     * the types listed above.  Bail for any other image
     * type.
     */
    return FALSE;
  }

  /* Create the GIMP image */
  theClientData->image_id = gimp_image_new(imageInfo->ImageWidth,
					   imageInfo->ImageLength, imageType);
  
  /* Set the actual resolution */
  gimp_image_set_resolution (theClientData->image_id,
                             FIX32ToFloat(imageInfo->XResolution),
                             FIX32ToFloat(imageInfo->YResolution));
  gimp_image_set_unit (theClientData->image_id, GIMP_UNIT_INCH);
  
  /* Create a layer */
  theClientData->layer_id = gimp_layer_new(theClientData->image_id,
					   _("Background"),
					   imageInfo->ImageWidth,
					   imageInfo->ImageLength,
					   layerType, 100, GIMP_NORMAL_MODE);

  /* Add the layer to the image */
  gimp_image_add_layer(theClientData->image_id,
		       theClientData->layer_id, 0);

  /* Update the progress dialog */
  theClientData->totalPixels = imageInfo->ImageWidth * imageInfo->ImageLength;
  theClientData->completedPixels = 0;
  gimp_progress_update((double) 0);

  /* Get our drawable */
  theClientData->drawable = gimp_drawable_get(theClientData->layer_id);

  /* Initialize a pixel region for writing to the image */
  gimp_pixel_rgn_init(&(theClientData->pixel_rgn), theClientData->drawable,
		      0, 0, imageInfo->ImageWidth, imageInfo->ImageLength,
		      TRUE, FALSE);

  /* Store our client data for the data transfer callbacks */
  if (clientData)
    g_free (clientData);
  setClientData(twSession, (void *) theClientData);

  /* Make sure to return TRUE to continue the image
   * transfer
   */
  return TRUE;
}

/*
 * bitTransferCallback
 *
 * The following function is called for each memory
 * block that is transferred from the data source if
 * the image type is Black/White.
 *
 * Black and white data is unpacked from bit data
 * into byte data and written into a gray scale GIMP
 * image.
 */
static char bitMasks[] = { 128, 64, 32, 16, 8, 4, 2, 1 };
static int
bitTransferCallback(pTW_IMAGEINFO imageInfo,
		    pTW_IMAGEMEMXFER imageMemXfer,
		    void *clientData)
{
  int row, col, offset;
  char *srcBuf;
  int rows = imageMemXfer->Rows;
  int cols = imageMemXfer->Columns;
  pClientDataStruct theClientData = (pClientDataStruct) clientData;

  /* Allocate a buffer as necessary */
  if (!destBuf)
    destBuf = g_new (char, rows * cols);

  /* Unpack the image data from bits into bytes */
  srcBuf = (char *) imageMemXfer->Memory.TheMem;
  offset = 0;
  for (row = 0; row < rows; row++) {
    for (col = 0; col < cols; col++) {
      char byte = srcBuf[(row * imageMemXfer->BytesPerRow) + (col / 8)];
      destBuf[offset++] = ((byte & bitMasks[col % 8]) != 0) ? 255 : 0;
    }
  }

  /* Update the complete chunk */
  gimp_pixel_rgn_set_rect(&(theClientData->pixel_rgn),
			  (guchar *) destBuf,
			  imageMemXfer->XOffset, imageMemXfer->YOffset,
			  cols, rows);

  /* Update the user on our progress */
  theClientData->completedPixels += (cols * rows);
  gimp_progress_update((double) theClientData->completedPixels /
		       (double) theClientData->totalPixels);

  return TRUE;
}

/*
 * oneBytePerSampleTransferCallback
 *
 * The following function is called for each memory
 * block that is transferred from the data source if
 * the image type is Grayscale or RGB.  This transfer
 * mode is quicker than the modes that require translation
 * from a greater number of bits per sample down to the
 * 8 bits per sample understood by The GIMP.
 */
static int
oneBytePerSampleTransferCallback(pTW_IMAGEINFO imageInfo,
		     pTW_IMAGEMEMXFER imageMemXfer,
		     void *clientData)
{
  int row;
  char *srcBuf;
  int bytesPerPixel = imageInfo->BitsPerPixel / 8;
  int rows = imageMemXfer->Rows;
  int cols = imageMemXfer->Columns;
  pClientDataStruct theClientData = (pClientDataStruct) clientData;

  /* Allocate a buffer as necessary */
  if (!destBuf)
    destBuf = g_new (char, rows * cols * bytesPerPixel);

  /* The bytes coming from the source may not be padded in
   * a way that The GIMP is terribly happy with.  It is
   * possible to transfer row by row, but that is particularly
   * expensive in terms of performance.  It is much cheaper
   * to rearrange the data and transfer it in one large chunk.
   * The next chunk of code rearranges the incoming data into
   * a non-padded chunk for The GIMP.
   */
  srcBuf = (char *) imageMemXfer->Memory.TheMem;
  for (row = 0; row < rows; row++) {
    /* Copy the current row */
    memcpy((destBuf + (row * bytesPerPixel * cols)),
	   (srcBuf + (row * imageMemXfer->BytesPerRow)),
	   (bytesPerPixel * cols));
  }

  /* Update the complete chunk */
  gimp_pixel_rgn_set_rect(&(theClientData->pixel_rgn),
			  (guchar *) destBuf,
			  imageMemXfer->XOffset, imageMemXfer->YOffset,
			  cols, rows);

  /* Update the user on our progress */
  theClientData->completedPixels += (cols * rows);
  gimp_progress_update((double) theClientData->completedPixels /
		       (double) theClientData->totalPixels);

  return TRUE;
}

/*
 * twoBytesPerSampleTransferCallback
 *
 * The following function is called for each memory
 * block that is transferred from the data source if
 * the image type is Grayscale or RGB.
 */
static int
twoBytesPerSampleTransferCallback(pTW_IMAGEINFO imageInfo,
		     pTW_IMAGEMEMXFER imageMemXfer,
		     void *clientData)
{
  static float ratio = 0.00390625;
  int row, col, sample;
  char *destByte;
  int rows = imageMemXfer->Rows;
  int cols = imageMemXfer->Columns;

  TW_UINT16 *samplePtr;

  pClientDataStruct theClientData = (pClientDataStruct) clientData;

  /* Allocate a buffer as necessary */
  if (!destBuf)
    destBuf = g_new (char, rows * cols * imageInfo->SamplesPerPixel);

  /* The bytes coming from the source may not be padded in
   * a way that The GIMP is terribly happy with.  It is
   * possible to transfer row by row, but that is particularly
   * expensive in terms of performance.  It is much cheaper
   * to rearrange the data and transfer it in one large chunk.
   * The next chunk of code rearranges the incoming data into
   * a non-padded chunk for The GIMP.  This function must also
   * reduce from multiple bytes per sample down to single byte
   * per sample.
   */
  /* Work through the rows */
  for (row = 0; row < rows; row++) {
    /* The start of this source row */
    samplePtr = (TW_UINT16 *)
      ((char *) imageMemXfer->Memory.TheMem + (row * imageMemXfer->BytesPerRow));

    /* The start of this dest row */
    destByte = destBuf + (row * imageInfo->SamplesPerPixel * cols);

    /* Work through the columns */
    for (col = 0; col < cols; col++) {
      /* Finally, work through each of the samples */
      for (sample = 0; sample < imageInfo->SamplesPerPixel; sample++) {
				/* Get the value */
	TW_UINT16 value = *samplePtr;

				/* Move the sample pointer */
	samplePtr++;

				/* Place in the destination */
	*destByte = (char) ((float) value * (float) ratio);
	destByte++;
      }
    }
  }

  /* Send the complete chunk */
  gimp_pixel_rgn_set_rect(&(theClientData->pixel_rgn),
			  (guchar *) destBuf,
			  imageMemXfer->XOffset, imageMemXfer->YOffset,
			  cols, rows);

  /* Update the user on our progress */
  theClientData->completedPixels += (cols * rows);
  gimp_progress_update((double) theClientData->completedPixels /
		       (double) theClientData->totalPixels);

  return TRUE;
}

/*
 * palettedTransferCallback
 *
 * The following function is called for each memory
 * block that is transferred from the data source if
 * the image type is paletted.  This does not create
 * an indexed image type in The GIMP because for some
 * reason it does not allow creation of a specific
 * palette.  This function will create an RGB or Gray
 * image and use the palette to set the details of
 * the pixels.
 */
static int
palettedTransferCallback(pTW_IMAGEINFO imageInfo,
			 pTW_IMAGEMEMXFER imageMemXfer,
			 void *clientData)
{
  int channelsPerEntry;
  int row, col;
  int rows = imageMemXfer->Rows;
  int cols = imageMemXfer->Columns;
  char *destPtr = NULL, *srcPtr = NULL;

  /* Get the client data */
  pClientDataStruct theClientData = (pClientDataStruct) clientData;

  /* Look up the palette entry size */
  channelsPerEntry =
    (theClientData->paletteData->PaletteType == TWPA_RGB) ? 3 : 1;

  /* Allocate a buffer as necessary */
  if (!destBuf)
    destBuf = g_new (char, rows * cols * channelsPerEntry);

  /* Work through the rows */
  destPtr = destBuf;
  for (row = 0; row < rows; row++) {
    srcPtr = (char *) ((char *) imageMemXfer->Memory.TheMem +
		       (row * imageMemXfer->BytesPerRow));

    /* Work through the columns */
    for (col = 0; col < cols; col++) {
      /* Get the palette index */
      int index = (unsigned char) *srcPtr;
      srcPtr++;

      switch (theClientData->paletteData->PaletteType) {
      case TWPA_GRAY:
	*destPtr = theClientData->paletteData->Colors[index].Channel1;
	destPtr++;
	break;

      case TWPA_RGB:
	*destPtr = theClientData->paletteData->Colors[index].Channel1;
	destPtr++;
	*destPtr = theClientData->paletteData->Colors[index].Channel2;
	destPtr++;
	*destPtr = theClientData->paletteData->Colors[index].Channel3;
	destPtr++;
      }
    }
  }

  /* Send the complete chunk */
  gimp_pixel_rgn_set_rect(&(theClientData->pixel_rgn),
			  (guchar *) destBuf,
			  imageMemXfer->XOffset, imageMemXfer->YOffset,
			  cols, rows);

  /* Update the user on our progress */
  theClientData->completedPixels += (cols * rows);
  gimp_progress_update((double) theClientData->completedPixels /
		       (double) theClientData->totalPixels);

  return TRUE;
}

/*
 * dataTransferCallback
 *
 * The following function is called for each memory
 * block that is transferred from the data source.
 */
int
dataTransferCallback(pTW_IMAGEINFO imageInfo,
		     pTW_IMAGEMEMXFER imageMemXfer,
		     void *clientData)
{
#ifdef _DEBUG
  logData(imageInfo, imageMemXfer, clientData);
#endif

  /* Choose the appropriate transfer handler */
  switch (imageInfo->PixelType) {
  case TWPT_PALETTE:
    return palettedTransferCallback(imageInfo, imageMemXfer, clientData);

  case TWPT_BW:
    return bitTransferCallback(imageInfo, imageMemXfer, clientData);

  case TWPT_GRAY:
  case TWPT_RGB:
    switch (imageInfo->BitsPerPixel / imageInfo->SamplesPerPixel) {
    case 8:
      return oneBytePerSampleTransferCallback(imageInfo, imageMemXfer, clientData);

    case 16:
      return twoBytesPerSampleTransferCallback(imageInfo, imageMemXfer, clientData);

    default:
      return FALSE;
    }

  default:
    return FALSE;
  }
}

/*
 * endTransferCallback
 *
 * The following function is called at the end of the
 * image transfer.  The caller will be handed
 * the image transfer completion state.  The
 * following values (defined in twain.h) are
 * possible:
 *
 * TWRC_XFERDONE
 *  The transfer completed successfully
 * TWRC_CANCEL
 *  The transfer was completed by the user
 * TWRC_FAILURE
 *  The transfer failed.
 */
int
endTransferCallback(int completionState, int pendingCount, void *clientData)
{
  pClientDataStruct theClientData = (pClientDataStruct) clientData;

  LogMessage("endTransferCallback: CompState = %d, pending = %d\n",
	     completionState, pendingCount);

  /* Clean up and detach from the drawable */
  if (destBuf) {
    g_free (destBuf);
    destBuf = NULL;
  }
  gimp_drawable_flush(theClientData->drawable);
  gimp_drawable_detach(theClientData->drawable);

  /* Make sure to check our return code */
  if (completionState == TWRC_XFERDONE) {
    /* We have a completed image transfer */
    values[2].type = GIMP_PDB_INT32ARRAY;
    values[2].data.d_int32array[values[1].data.d_int32++] =
      theClientData->image_id;

    /* Display the image */
    LogMessage("Displaying image %d\n", theClientData->image_id);
    gimp_display_new (theClientData->image_id);
  } else {
    /* The transfer did not complete successfully */
    LogMessage("Deleting image\n");
    gimp_image_delete(theClientData->image_id);
  }

  /* Shut down if we have received all of the possible images */
  return (values[1].data.d_int32 < MAX_IMAGES);
}

/*
 * postTransferCallback
 *
 * This callback function will be called
 * after all possible images have been
 * transferred.
 */
void
postTransferCallback(int pendingCount, void *clientData)
{
  /* Shut things down. */
  if (pendingCount != 0)
    cancelPendingTransfers(twSession);

  /* This will close the datasource and datasource
   * manager.  Then the message queue will be shut
   * down and the run() procedure will finally be
   * able to finish.
   */
  disableDS(twSession);
  closeDS(twSession);
  closeDSM(twSession);

  /* Post a message to close up the application */
  twainQuitApplication ();
}
