/* bmpread.c    reads any bitmap I could get for testing */
/* Alexander.Schulz@stud.uni-karlsruhe.de                */

/*
 * GIMP - The GNU Image Manipulation Program
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * 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 3 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, see <https://www.gnu.org/licenses/>.
 * ----------------------------------------------------------------------------
 */

#include "config.h"

#include <errno.h>
#include <string.h>

#include <glib/gstdio.h>

#include <libgimp/gimp.h>

#include "bmp.h"
#include "bmp-load.h"

#include "libgimp/stdplugins-intl.h"


#if !defined(WIN32) || defined(__MINGW32__)
#define BI_RGB            0
#define BI_RLE8           1
#define BI_RLE4           2
#define BI_BITFIELDS      3
#define BI_ALPHABITFIELDS 4
#endif


static GimpImage * ReadImage (FILE                 *fd,
                              GFile                *file,
                              gint                  width,
                              gint                  height,
                              guchar                cmap[256][3],
                              gint                  ncols,
                              gint                  bpp,
                              gint                  compression,
                              gint                  rowbytes,
                              gboolean              gray,
                              const BitmapChannel  *masks,
                              GError              **error);


static void
setMasksDefault (gushort        biBitCnt,
                 BitmapChannel *masks)
{
  switch (biBitCnt)
    {
    case 32:
      masks[0].mask      = 0x00ff0000;
      masks[0].shiftin   = 16;
      masks[0].max_value = (gfloat)255.0;
      masks[1].mask      = 0x0000ff00;
      masks[1].shiftin   = 8;
      masks[1].max_value = (gfloat)255.0;
      masks[2].mask      = 0x000000ff;
      masks[2].shiftin   = 0;
      masks[2].max_value = (gfloat)255.0;
      masks[3].mask      = 0x00000000;
      masks[3].shiftin   = 0;
      masks[3].max_value = (gfloat)0.0;
      break;

    case 24:
      masks[0].mask      = 0xff0000;
      masks[0].shiftin   = 16;
      masks[0].max_value = (gfloat)255.0;
      masks[1].mask      = 0x00ff00;
      masks[1].shiftin   = 8;
      masks[1].max_value = (gfloat)255.0;
      masks[2].mask      = 0x0000ff;
      masks[2].shiftin   = 0;
      masks[2].max_value = (gfloat)255.0;
      masks[3].mask      = 0x0;
      masks[3].shiftin   = 0;
      masks[3].max_value = (gfloat)0.0;
      break;

    case 16:
      masks[0].mask      = 0x7c00;
      masks[0].shiftin   = 10;
      masks[0].max_value = (gfloat)31.0;
      masks[1].mask      = 0x03e0;
      masks[1].shiftin   = 5;
      masks[1].max_value = (gfloat)31.0;
      masks[2].mask      = 0x001f;
      masks[2].shiftin   = 0;
      masks[2].max_value = (gfloat)31.0;
      masks[3].mask      = 0x0;
      masks[3].shiftin   = 0;
      masks[3].max_value = (gfloat)0.0;
      break;

    default:
      break;
    }
}

static gint32
ToL (const guchar *buffer)
{
  return (buffer[0] | buffer[1] << 8 | buffer[2] << 16 | buffer[3] << 24);
}

static gint16
ToS (const guchar *buffer)
{
  return (buffer[0] | buffer[1] << 8);
}

static gboolean
ReadColorMap (FILE     *fd,
              guchar    buffer[256][3],
              gint      number,
              gint      size,
              gboolean *gray)
{
  gint i;

  *gray = (number > 2);

  for (i = 0; i < number ; i++)
    {
      guchar rgb[4];

      if (! ReadOK (fd, rgb, size))
        {
          g_message (_("Bad colormap"));
          return FALSE;
        }

      /* Bitmap save the colors in another order! But change only once! */

      buffer[i][0] = rgb[2];
      buffer[i][1] = rgb[1];
      buffer[i][2] = rgb[0];

      *gray = ((*gray) && (rgb[0] == rgb[1]) && (rgb[1] == rgb[2]));
    }

  return TRUE;
}

static gboolean
ReadChannelMasks (guint32       *tmp,
                  BitmapChannel *masks,
                  guint          channels)
{
  gint i;

  for (i = 0; i < channels; i++)
    {
      guint32 mask;
      gint    nbits, offset, bit;

      mask = tmp[i];
      masks[i].mask = mask;
      nbits = 0;
      offset = -1;

      for (bit = 0; bit < 32; bit++)
        {
          if (mask & 1)
            {
              nbits++;
              if (offset == -1)
                offset = bit;
            }

          mask = mask >> 1;
        }

      masks[i].shiftin   = offset;
      masks[i].max_value = (gfloat) ((1 << nbits) - 1);

#ifdef DEBUG
      g_print ("Channel %d mask %08x in %d max_val %d\n",
               i, masks[i].mask, masks[i].shiftin, (gint)masks[i].max_value);
#endif
    }

  return TRUE;
}

GimpImage *
load_image (GFile  *file,
            GError **error)
{
  FILE           *fd;
  BitmapFileHead  bitmap_file_head;
  BitmapHead      bitmap_head;
  guchar          buffer[124];
  gint            ColormapSize, rowbytes, Maps;
  gboolean        gray = FALSE;
  guchar          ColorMap[256][3];
  GimpImage      *image = NULL;
  gchar           magick[2];
  BitmapChannel   masks[4];

  gimp_progress_init_printf (_("Opening '%s'"),
                             gimp_file_get_utf8_name (file));

  fd = g_fopen (g_file_peek_path (file), "rb");

  if (! fd)
    {
      g_set_error (error, G_FILE_ERROR, g_file_error_from_errno (errno),
                   _("Could not open '%s' for reading: %s"),
                   gimp_file_get_utf8_name (file), g_strerror (errno));
      goto out;
    }

  /* It is a File. Now is it a Bitmap? Read the shortest possible header */

  if (! ReadOK (fd, magick, 2) ||
      ! (! strncmp (magick, "BA", 2) ||
         ! strncmp (magick, "BM", 2) ||
         ! strncmp (magick, "IC", 2) ||
         ! strncmp (magick, "PT", 2) ||
         ! strncmp (magick, "CI", 2) ||
         ! strncmp (magick, "CP", 2)))
    {
      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                   _("'%s' is not a valid BMP file"),
                   gimp_file_get_utf8_name (file));
      goto out;
    }

  while (! strncmp (magick, "BA", 2))
    {
      if (! ReadOK (fd, buffer, 12))
        {
          g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                       _("'%s' is not a valid BMP file"),
                       gimp_file_get_utf8_name (file));
          goto out;
        }

      if (! ReadOK (fd, magick, 2))
        {
          g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                       _("'%s' is not a valid BMP file"),
                       gimp_file_get_utf8_name (file));
          goto out;
        }
    }

  if (! ReadOK (fd, buffer, 12))
    {
      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                   _("'%s' is not a valid BMP file"),
                   gimp_file_get_utf8_name (file));
      goto out;
    }

  /* bring them to the right byteorder. Not too nice, but it should work */

  bitmap_file_head.bfSize = ToL (&buffer[0x00]);
  bitmap_file_head.zzHotX = ToS (&buffer[0x04]);
  bitmap_file_head.zzHotY = ToS (&buffer[0x06]);
  bitmap_file_head.bfOffs = ToL (&buffer[0x08]);

  if (! ReadOK (fd, buffer, 4))
    {
      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                   _("'%s' is not a valid BMP file"),
                   gimp_file_get_utf8_name (file));
      goto out;
    }

  bitmap_file_head.biSize = ToL (&buffer[0x00]);

  /* What kind of bitmap is it? */

  if (bitmap_file_head.biSize == 12) /* OS/2 1.x ? */
    {
      if (! ReadOK (fd, buffer, 8))
        {
          g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                       _("Error reading BMP file header from '%s'"),
                       gimp_file_get_utf8_name (file));
          goto out;
        }

      bitmap_head.biWidth   = ToS (&buffer[0x00]);       /* 12 */
      bitmap_head.biHeight  = ToS (&buffer[0x02]);       /* 14 */
      bitmap_head.biPlanes  = ToS (&buffer[0x04]);       /* 16 */
      bitmap_head.biBitCnt  = ToS (&buffer[0x06]);       /* 18 */
      bitmap_head.biCompr   = 0;
      bitmap_head.biSizeIm  = 0;
      bitmap_head.biXPels   = bitmap_head.biYPels = 0;
      bitmap_head.biClrUsed = 0;
      bitmap_head.biClrImp  = 0;
      bitmap_head.masks[0]  = 0;
      bitmap_head.masks[1]  = 0;
      bitmap_head.masks[2]  = 0;
      bitmap_head.masks[3]  = 0;

      memset (masks, 0, sizeof (masks));
      Maps = 3;
    }
  else if (bitmap_file_head.biSize == 40) /* Windows 3.x */
    {
      if (! ReadOK (fd, buffer, 36))
        {
          g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                       _("Error reading BMP file header from '%s'"),
                       gimp_file_get_utf8_name (file));
          goto out;
        }

      bitmap_head.biWidth   = ToL (&buffer[0x00]);      /* 12 */
      bitmap_head.biHeight  = ToL (&buffer[0x04]);      /* 16 */
      bitmap_head.biPlanes  = ToS (&buffer[0x08]);      /* 1A */
      bitmap_head.biBitCnt  = ToS (&buffer[0x0A]);      /* 1C */
      bitmap_head.biCompr   = ToL (&buffer[0x0C]);      /* 1E */
      bitmap_head.biSizeIm  = ToL (&buffer[0x10]);      /* 22 */
      bitmap_head.biXPels   = ToL (&buffer[0x14]);      /* 26 */
      bitmap_head.biYPels   = ToL (&buffer[0x18]);      /* 2A */
      bitmap_head.biClrUsed = ToL (&buffer[0x1C]);      /* 2E */
      bitmap_head.biClrImp  = ToL (&buffer[0x20]);      /* 32 */
      bitmap_head.masks[0]  = 0;
      bitmap_head.masks[1]  = 0;
      bitmap_head.masks[2]  = 0;
      bitmap_head.masks[3]  = 0;

      Maps = 4;
      memset (masks, 0, sizeof (masks));

      if (bitmap_head.biCompr == BI_BITFIELDS)
        {
#ifdef DEBUG
          g_print ("Got BI_BITFIELDS compression\n");
#endif

          if (! ReadOK (fd, buffer, 3 * sizeof (guint32)))
            {
              g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                           _("Error reading BMP file header from '%s'"),
                           gimp_file_get_utf8_name (file));
              goto out;
            }

          bitmap_head.masks[0] = ToL (&buffer[0x00]);
          bitmap_head.masks[1] = ToL (&buffer[0x04]);
          bitmap_head.masks[2] = ToL (&buffer[0x08]);

          ReadChannelMasks (&bitmap_head.masks[0], masks, 3);
        }
      else if (bitmap_head.biCompr == BI_RGB)
        {
#ifdef DEBUG
          g_print ("Got BI_RGB compression\n");
#endif

          setMasksDefault (bitmap_head.biBitCnt, masks);
        }
      else if ((bitmap_head.biCompr != BI_RLE4) &&
               (bitmap_head.biCompr != BI_RLE8))
        {
          /* BI_ALPHABITFIELDS, etc. */
          g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                       _("Unsupported compression (%u) in BMP file from '%s'"),
                       bitmap_head.biCompr,
                       gimp_file_get_utf8_name (file));
          goto out;
        }

#ifdef DEBUG
      g_print ("Got BI_RLE4 or BI_RLE8 compression\n");
#endif
    }
  else if (bitmap_file_head.biSize >= 56 &&
           bitmap_file_head.biSize <= 64)
    {
      /* enhanced Windows format with bit masks */

      if (! ReadOK (fd, buffer, bitmap_file_head.biSize - 4))
        {
          g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                       _("Error reading BMP file header from '%s'"),
                       gimp_file_get_utf8_name (file));
          goto out;
        }

      bitmap_head.biWidth   = ToL (&buffer[0x00]);       /* 12 */
      bitmap_head.biHeight  = ToL (&buffer[0x04]);       /* 16 */
      bitmap_head.biPlanes  = ToS (&buffer[0x08]);       /* 1A */
      bitmap_head.biBitCnt  = ToS (&buffer[0x0A]);       /* 1C */
      bitmap_head.biCompr   = ToL (&buffer[0x0C]);       /* 1E */
      bitmap_head.biSizeIm  = ToL (&buffer[0x10]);       /* 22 */
      bitmap_head.biXPels   = ToL (&buffer[0x14]);       /* 26 */
      bitmap_head.biYPels   = ToL (&buffer[0x18]);       /* 2A */
      bitmap_head.biClrUsed = ToL (&buffer[0x1C]);       /* 2E */
      bitmap_head.biClrImp  = ToL (&buffer[0x20]);       /* 32 */
      bitmap_head.masks[0]  = ToL (&buffer[0x24]);       /* 36 */
      bitmap_head.masks[1]  = ToL (&buffer[0x28]);       /* 3A */
      bitmap_head.masks[2]  = ToL (&buffer[0x2C]);       /* 3E */
      bitmap_head.masks[3]  = ToL (&buffer[0x30]);       /* 42 */

      Maps = 4;
      ReadChannelMasks (&bitmap_head.masks[0], masks, 4);
    }
  else if (bitmap_file_head.biSize == 108 ||
           bitmap_file_head.biSize == 124)
    {
      /* BMP Version 4 or 5 */

      if (! ReadOK (fd, buffer, bitmap_file_head.biSize - 4))
        {
          g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                       _("Error reading BMP file header from '%s'"),
                       gimp_file_get_utf8_name (file));
          goto out;
        }

      bitmap_head.biWidth   = ToL (&buffer[0x00]);
      bitmap_head.biHeight  = ToL (&buffer[0x04]);
      bitmap_head.biPlanes  = ToS (&buffer[0x08]);
      bitmap_head.biBitCnt  = ToS (&buffer[0x0A]);
      bitmap_head.biCompr   = ToL (&buffer[0x0C]);
      bitmap_head.biSizeIm  = ToL (&buffer[0x10]);
      bitmap_head.biXPels   = ToL (&buffer[0x14]);
      bitmap_head.biYPels   = ToL (&buffer[0x18]);
      bitmap_head.biClrUsed = ToL (&buffer[0x1C]);
      bitmap_head.biClrImp  = ToL (&buffer[0x20]);
      bitmap_head.masks[0]  = ToL (&buffer[0x24]);
      bitmap_head.masks[1]  = ToL (&buffer[0x28]);
      bitmap_head.masks[2]  = ToL (&buffer[0x2C]);
      bitmap_head.masks[3]  = ToL (&buffer[0x30]);

      Maps = 4;

      if (bitmap_head.biCompr == BI_BITFIELDS)
        {
#ifdef DEBUG
          g_print ("Got BI_BITFIELDS compression\n");
#endif

          ReadChannelMasks (&bitmap_head.masks[0], masks, 4);
        }
      else if (bitmap_head.biCompr == BI_RGB)
        {
#ifdef DEBUG
          g_print ("Got BI_RGB compression\n");
#endif

          setMasksDefault (bitmap_head.biBitCnt, masks);
        }
    }
  else
    {
      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                   _("Error reading BMP file header from '%s'"),
                   gimp_file_get_utf8_name (file));
      goto out;
    }

  /* Valid bit depth is 1, 4, 8, 16, 24, 32 */
  /* 16 is awful, we should probably shoot whoever invented it */

  switch (bitmap_head.biBitCnt)
    {
    case 1:
    case 2:
    case 4:
    case 8:
    case 16:
    case 24:
    case 32:
      break;
    default:
      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                   _("'%s' is not a valid BMP file"),
                   gimp_file_get_utf8_name (file));
      goto out;
    }

  /* There should be some colors used! */

  ColormapSize =
    (bitmap_file_head.bfOffs - bitmap_file_head.biSize - 14) / Maps;

  if ((bitmap_head.biClrUsed == 0) &&
      (bitmap_head.biBitCnt  <= 8))
    {
      ColormapSize = bitmap_head.biClrUsed = 1 << bitmap_head.biBitCnt;
    }

  if (ColormapSize > 256)
    ColormapSize = 256;

  /* Sanity checks */

  if (bitmap_head.biHeight == 0 ||
      bitmap_head.biWidth  == 0)
    {
      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                   _("'%s' is not a valid BMP file"),
                   gimp_file_get_utf8_name (file));
      goto out;
    }

  /* biHeight may be negative, but G_MININT32 is dangerous because:
     G_MININT32 == -(G_MININT32) */
  if (bitmap_head.biWidth  <  0 ||
      bitmap_head.biHeight == G_MININT32)
    {
      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                   _("'%s' is not a valid BMP file"),
                   gimp_file_get_utf8_name (file));
      goto out;
    }

  if (bitmap_head.biPlanes != 1)
    {
      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                   _("'%s' is not a valid BMP file"),
                   gimp_file_get_utf8_name (file));
      goto out;
    }

  if (bitmap_head.biClrUsed >  256 &&
      bitmap_head.biBitCnt  <= 8)
    {
      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                   _("'%s' is not a valid BMP file"),
                   gimp_file_get_utf8_name (file));
      goto out;
    }

  /* protect against integer overflows caused by malicious BMPs */
  /* use divisions in comparisons to avoid type overflows */

  if (((guint64) bitmap_head.biWidth) > G_MAXINT32 / bitmap_head.biBitCnt ||
      ((guint64) bitmap_head.biWidth) > (G_MAXINT32 / ABS (bitmap_head.biHeight)) / 4)
    {
      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                   _("'%s' is not a valid BMP file"),
                   gimp_file_get_utf8_name (file));
      goto out;
    }

  /* Windows and OS/2 declare filler so that rows are a multiple of
   * word length (32 bits == 4 bytes)
   */

  rowbytes = ((bitmap_head.biWidth * bitmap_head.biBitCnt - 1) / 32) * 4 + 4;

#ifdef DEBUG
  printf ("\nSize: %lu, Colors: %lu, Bits: %hu, Width: %ld, Height: %ld, "
          "Comp: %lu, Zeile: %d\n",
          bitmap_file_head.bfSize,
          bitmap_head.biClrUsed,
          bitmap_head.biBitCnt,
          bitmap_head.biWidth,
          bitmap_head.biHeight,
          bitmap_head.biCompr,
          rowbytes);
#endif

  if (bitmap_head.biBitCnt <= 8)
    {
#ifdef DEBUG
      printf ("Colormap read\n");
#endif
      /* Get the Colormap */
      if (! ReadColorMap (fd, ColorMap, ColormapSize, Maps, &gray))
        goto out;
    }

  fseek (fd, bitmap_file_head.bfOffs, SEEK_SET);

  /* Get the Image and return the image or NULL on error*/
  image = ReadImage (fd,
                     file,
                     bitmap_head.biWidth,
                     ABS (bitmap_head.biHeight),
                     ColorMap,
                     bitmap_head.biClrUsed,
                     bitmap_head.biBitCnt,
                     bitmap_head.biCompr,
                     rowbytes,
                     gray,
                     masks,
                     error);

  if (! image)
    goto out;

  if (bitmap_head.biXPels > 0 &&
      bitmap_head.biYPels > 0)
    {
      /* Fixed up from scott@asofyet's changes last year, njl195 */
      gdouble xresolution;
      gdouble yresolution;

      /* I don't agree with scott's feeling that Gimp should be trying
       * to "fix" metric resolution translations, in the long term
       * Gimp should be SI (metric) anyway, but we haven't told the
       * Americans that yet
       */

      xresolution = bitmap_head.biXPels * 0.0254;
      yresolution = bitmap_head.biYPels * 0.0254;

      gimp_image_set_resolution (image, xresolution, yresolution);
    }

  if (bitmap_head.biHeight < 0)
    gimp_image_flip (image, GIMP_ORIENTATION_VERTICAL);

out:
  if (fd)
    fclose (fd);

  return image;
}

static GimpImage *
ReadImage (FILE                 *fd,
           GFile                *file,
           gint                  width,
           gint                  height,
           guchar                cmap[256][3],
           gint                  ncols,
           gint                  bpp,
           gint                  compression,
           gint                  rowbytes,
           gboolean              gray,
           const BitmapChannel  *masks,
           GError              **error)
{
  guchar             v, n;
  gint               xpos = 0;
  gint               ypos = 0;
  GimpImage         *image;
  GimpLayer         *layer;
  GeglBuffer        *buffer;
  guchar            *dest, *temp, *row_buf;
  guchar             gimp_cmap[768];
  gushort            rgb;
  glong              rowstride, channels;
  gint               i, i_max, j, cur_progress, max_progress;
  gint               total_bytes_read;
  GimpImageBaseType  base_type;
  GimpImageType      image_type;
  guint32            px32;

  if (! (compression == BI_RGB || compression == BI_BITFIELDS ||
      (bpp == 8 && compression == BI_RLE8) ||
      (bpp == 4 && compression == BI_RLE4)))
    {
      g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                   "%s",
                   _("Unrecognized or invalid BMP compression format."));
      return NULL;
    }

  /* Make a new image in GIMP */

  switch (bpp)
    {
    case 32:
    case 24:
    case 16:
      base_type = GIMP_RGB;
      if (masks[3].mask != 0)
        {
          image_type = GIMP_RGBA_IMAGE;
          channels = 4;
        }
      else
        {
          image_type = GIMP_RGB_IMAGE;
          channels = 3;
        }
      if (bpp == 24 && compression == BI_BITFIELDS)
        g_printerr ("Loading BMP with invalid combination of 24 bpp and BI_BITFIELDS compression.\n");
      break;

    case 8:
    case 4:
    case 1:
      if (gray)
        {
          base_type = GIMP_GRAY;
          image_type = GIMP_GRAY_IMAGE;
        }
      else
        {
          base_type = GIMP_INDEXED;
          image_type = GIMP_INDEXED_IMAGE;
        }
      if (compression == BI_BITFIELDS)
        g_printerr ("Loading BMP with invalid combination of %d bpp and BI_BITFIELDS compression.\n",
                    bpp);

      channels = 1;
      break;

    default:
      g_message (_("Unsupported or invalid bitdepth."));
      return NULL;
    }

  if ((width < 0) || (width > GIMP_MAX_IMAGE_SIZE))
    {
      g_message (_("Unsupported or invalid image width: %d"), width);
      return NULL;
    }

  if ((height < 0) || (height > GIMP_MAX_IMAGE_SIZE))
    {
      g_message (_("Unsupported or invalid image height: %d"), height);
      return NULL;
    }

  image = gimp_image_new (width, height, base_type);
  layer = gimp_layer_new (image, _("Background"),
                          width, height,
                          image_type, 100,
                          gimp_image_get_default_new_layer_mode (image));
  gimp_image_insert_layer (image, layer, NULL, 0);

  /* use g_malloc0 to initialize the dest buffer so that unspecified
     pixels in RLE bitmaps show up as the zeroth element in the palette.
  */
  dest      = g_malloc0 (width * height * channels);
  row_buf   = g_malloc (rowbytes);
  rowstride = width * channels;

  ypos = height - 1;  /* Bitmaps begin in the lower left corner */
  cur_progress = 0;
  max_progress = height;

  switch (bpp)
    {
    case 32:
      {
        while (ReadOK (fd, row_buf, rowbytes))
          {
            temp = dest + (ypos * rowstride);

            for (xpos= 0; xpos < width; ++xpos)
              {
                px32 = ToL(&row_buf[xpos*4]);
                *(temp++) = ((px32 & masks[0].mask) >> masks[0].shiftin) * 255.0 / masks[0].max_value + 0.5;
                *(temp++) = ((px32 & masks[1].mask) >> masks[1].shiftin) * 255.0 / masks[1].max_value + 0.5;
                *(temp++) = ((px32 & masks[2].mask) >> masks[2].shiftin) * 255.0 / masks[2].max_value + 0.5;
                if (channels > 3)
                  *(temp++) = ((px32 & masks[3].mask) >> masks[3].shiftin) * 255.0 / masks[3].max_value + 0.5;
              }

            if (ypos == 0)
              break;

            --ypos; /* next line */

            cur_progress++;
            if ((cur_progress % 5) == 0)
              gimp_progress_update ((gdouble) cur_progress /
                                    (gdouble) max_progress);
          }
      }
      break;

    case 24:
      {
        while (ReadOK (fd, row_buf, rowbytes))
          {
            temp = dest + (ypos * rowstride);

            for (xpos= 0; xpos < width; ++xpos)
              {
                *(temp++) = row_buf[xpos * 3 + 2];
                *(temp++) = row_buf[xpos * 3 + 1];
                *(temp++) = row_buf[xpos * 3];
              }

            if (ypos == 0)
              break;

            --ypos; /* next line */

            cur_progress++;
            if ((cur_progress % 5) == 0)
              gimp_progress_update ((gdouble) cur_progress /
                                    (gdouble) max_progress);
          }
      }
      break;

    case 16:
      {
        while (ReadOK (fd, row_buf, rowbytes))
          {
            temp = dest + (ypos * rowstride);

            for (xpos= 0; xpos < width; ++xpos)
              {
                rgb= ToS(&row_buf[xpos * 2]);
                *(temp++) = ((rgb & masks[0].mask) >> masks[0].shiftin) * 255.0 / masks[0].max_value + 0.5;
                *(temp++) = ((rgb & masks[1].mask) >> masks[1].shiftin) * 255.0 / masks[1].max_value + 0.5;
                *(temp++) = ((rgb & masks[2].mask) >> masks[2].shiftin) * 255.0 / masks[2].max_value + 0.5;
                if (channels > 3)
                  *(temp++) = ((rgb & masks[3].mask) >> masks[3].shiftin) * 255.0 / masks[3].max_value + 0.5;
              }

            if (ypos == 0)
              break;

            --ypos; /* next line */

            cur_progress++;
            if ((cur_progress % 5) == 0)
              gimp_progress_update ((gdouble) cur_progress /
                                    (gdouble) max_progress);
          }
      }
      break;

    case 8:
    case 4:
    case 1:
      {
        if (compression == BI_RGB || compression == BI_BITFIELDS)
          /* no compression */
          {
            while (ReadOK (fd, &v, 1))
              {
                for (i = 1; (i <= (8 / bpp)) && (xpos < width); i++, xpos++)
                  {
                    temp = dest + (ypos * rowstride) + (xpos * channels);
                    *temp=( v & ( ((1<<bpp)-1) << (8-(i*bpp)) ) ) >> (8-(i*bpp));
                    if (gray)
                      *temp = cmap[*temp][0];
                  }

                if (xpos == width)
                  {
                    fread (row_buf, rowbytes - 1 - (width * bpp - 1) / 8, 1, fd);

                    if (ypos == 0)
                      break;

                    ypos--;
                    xpos = 0;

                    cur_progress++;
                    if ((cur_progress % 5) == 0)
                      gimp_progress_update ((gdouble) cur_progress /
                                            (gdouble) max_progress);
                  }

                if (ypos < 0)
                  break;
              }
            break;
          }
        else
          {
            /* compressed image (either RLE8 or RLE4) */
            while (ypos >= 0 && xpos <= width)
              {
                if (! ReadOK (fd, row_buf, 2))
                  {
                    g_message (_("The bitmap ends unexpectedly."));
                    break;
                  }

                if (row_buf[0] != 0)
                  /* Count + Color - record */
                  {
                    /* encoded mode run -
                     *   row_buf[0] == run_length
                     *   row_buf[1] == pixel data
                     */
                    for (j = 0;
                         ((guchar) j < row_buf[0]) && (xpos < width);)
                      {
#ifdef DEBUG2
                        printf("%u %u | ",xpos,width);
#endif
                        for (i = 1;
                             ((i <= (8 / bpp)) &&
                              (xpos < width) &&
                              ((guchar) j < row_buf[0]));
                             i++, xpos++, j++)
                          {
                            temp = dest + (ypos * rowstride) + (xpos * channels);
                            *temp = (row_buf[1] &
                                     (((1<<bpp)-1) << (8 - (i * bpp)))) >> (8 - (i * bpp));
                            if (gray)
                              *temp = cmap[*temp][0];
                          }
                      }
                  }

                if ((row_buf[0] == 0) && (row_buf[1] > 2))
                  /* uncompressed record */
                  {
                    n = row_buf[1];
                    total_bytes_read = 0;

                    for (j = 0; j < n; j += (8 / bpp))
                      {
                        /* read the next byte in the record */
                        if (! ReadOK (fd, &v, 1))
                          {
                            g_message (_("The bitmap ends unexpectedly."));
                            break;
                          }

                        total_bytes_read++;

                        /* read all pixels from that byte */
                        i_max = 8 / bpp;
                        if (n - j < i_max)
                          {
                            i_max = n - j;
                          }

                        i = 1;
                        while ((i <= i_max) && (xpos < width))
                          {
                            temp =
                              dest + (ypos * rowstride) + (xpos * channels);
                            *temp = (v >> (8-(i*bpp))) & ((1<<bpp)-1);
                            if (gray)
                              *temp = cmap[*temp][0];
                            i++;
                            xpos++;
                          }
                      }

                    /* absolute mode runs are padded to 16-bit alignment */
                    if (total_bytes_read % 2)
                      fread (&v, 1, 1, fd);
                  }

                if ((row_buf[0] == 0) && (row_buf[1] == 0))
                  /* Line end */
                  {
                    ypos--;
                    xpos = 0;

                    cur_progress++;
                    if ((cur_progress % 5) == 0)
                      gimp_progress_update ((gdouble) cur_progress /
                                            (gdouble)  max_progress);
                  }

                if ((row_buf[0] == 0) && (row_buf[1] == 1))
                  /* Bitmap end */
                  {
                    break;
                  }

                if ((row_buf[0] == 0) && (row_buf[1] == 2))
                  /* Deltarecord */
                  {
                    if (! ReadOK (fd, row_buf, 2))
                      {
                        g_message (_("The bitmap ends unexpectedly."));
                        break;
                      }

                    xpos += row_buf[0];
                    ypos -= row_buf[1];
                  }
              }
            break;
          }
      }
      break;

    default:
      g_assert_not_reached ();
      break;
    }

  if (bpp <= 8)
    for (i = 0, j = 0; i < ncols; i++)
      {
        gimp_cmap[j++] = cmap[i][0];
        gimp_cmap[j++] = cmap[i][1];
        gimp_cmap[j++] = cmap[i][2];
      }

  buffer = gimp_drawable_get_buffer (GIMP_DRAWABLE (layer));

  gegl_buffer_set (buffer, GEGL_RECTANGLE (0, 0, width, height), 0,
                   NULL, dest, GEGL_AUTO_ROWSTRIDE);

  g_object_unref (buffer);

  g_free (dest);

  if ((! gray) && (bpp <= 8))
    gimp_image_set_colormap (image, gimp_cmap, ncols);

  gimp_progress_update (1.0);

  return image;
}
