From e51ca66ee5397f527da309deea5f40d5e7cfef3f Mon Sep 17 00:00:00 2001
From: Jacob Boerema <jgboerema@gmail.com>
Date: Tue, 18 Jan 2022 16:30:28 -0500
Subject: [PATCH] plug-ins: fix #7524 DICOM File is broken

This is the same issue as with IM000001.dcm mentioned in issue #313.

There are two problems: incorrect endian conversion for 16 bits per pixel,
and not handling photometric interpretation "MONOCHROME1", which means
minimum value is white instead of black.

The endian conversion was fixed as suggested in issue #313.
For "MONOCHROME1" we added a variable bw_inverted and we invert the pixel
value if that variable is true.
---
 plug-ins/common/file-dicom.c | 58 ++++++++++++++++++++++++++++++++++--
 1 file changed, 56 insertions(+), 2 deletions(-)

diff --git a/plug-ins/common/file-dicom.c b/plug-ins/common/file-dicom.c
index 2d2a160c2a..e1d282c982 100644
--- a/plug-ins/common/file-dicom.c
+++ b/plug-ins/common/file-dicom.c
@@ -58,6 +58,7 @@ typedef struct _DicomInfo
   gint       high_bit;
   gboolean   is_signed;
   gboolean   planar;
+  gboolean   bw_inverted;
 } DicomInfo;
 
 
@@ -583,6 +584,8 @@ load_image (GFile   *file,
         }
       else if (group_word == 0x0028)
         {
+          gboolean supported = TRUE;
+
           switch (element_word)
             {
             case 0x0002:  /* samples per pixel */
@@ -590,7 +593,49 @@ load_image (GFile   *file,
               g_debug ("spp: %d", samples_per_pixel);
               break;
             case 0x0004:  /* photometric interpretation */
-              g_debug ("photometric interpretation: %s", (char*) value);
+              g_debug ("photometric interpretation: %s", (gchar *) value);
+
+              if (samples_per_pixel == 1)
+                {
+                  if (strncmp ((gchar *) value, "MONOCHROME1", 11) == 0)
+                    {
+                      /* The minimum sample value is intended to be displayed
+                       * as white after any VOI gray scale transformations
+                       * have been performed. */
+                      dicominfo->bw_inverted = TRUE;
+                    }
+                  else if (strncmp ((gchar *) value, "MONOCHROME2", 11) == 0)
+                    {
+                      /* The minimum sample value is intended to be displayed
+                       * as black after any VOI gray scale transformations
+                       * have been performed. */
+                      dicominfo->bw_inverted = FALSE;
+                    }
+                  else
+                    supported = FALSE;
+                }
+              else if (samples_per_pixel == 3)
+                {
+                  if (strncmp ((gchar *) value, "RGB", 2) != 0)
+                    {
+                      supported = FALSE;
+                    }
+                }
+              else
+                {
+                  supported = FALSE;
+                }
+              if (! supported)
+                {
+                  g_set_error (error, GIMP_PLUG_IN_ERROR, 0,
+                               _("%s is not supported by GIMP in combination "
+                                 "with samples per pixel: %d"),
+                               (gchar *) value, samples_per_pixel);
+                  g_free (dicominfo);
+                  fclose (dicom);
+                  return NULL;
+                }
+
               break;
             case 0x0006:  /* planar configuration */
               g_debug ("planar configuration: %u", ctx_us);
@@ -758,7 +803,7 @@ dicom_loader (guint8     *pix_buffer,
        * (i.e., compensate for high_bit and bits_stored).
        */
       for (pix_idx = 0; pix_idx < width * height * samples_per_pixel; pix_idx++)
-        buf16[pix_idx] = g_htons (buf16[pix_idx]) >> shift;
+        buf16[pix_idx] = g_ntohs (GUINT16_SWAP_LE_BE  (buf16[pix_idx])) >> shift;
     }
 
   data = g_malloc (gimp_tile_height () * width * samples_per_pixel);
@@ -793,6 +838,11 @@ dicom_loader (guint8     *pix_buffer,
                    */
                   d[col_idx] = (guint8) (row_start[col_idx] >>
                                          (info->bits_stored - 8));
+                  if (info->bw_inverted)
+                    {
+                      d[col_idx] = ~d[col_idx];
+                    }
+
                   if (info->is_signed)
                     {
                       /* If the data is negative, make it 0. Otherwise,
@@ -822,6 +872,10 @@ dicom_loader (guint8     *pix_buffer,
                        * less than bpp.
                        */
                       d[col_idx] = row_start[col_idx] << (8 - info->bits_stored);
+                      if (info->bw_inverted)
+                        {
+                          d[col_idx] = ~d[col_idx];
+                        }
 
                       if (info->is_signed)
                         {