fix handling of AT

We were treating AT as a string rather than a fixed length numeric
array. Improve display with dcm-dump as well.

Author: jcupitt

src/dicom-data.c

@@ -1223,6 +1223,11 @@ char *dcm_element_value_to_string(const DcmElement *element)
                     result = dcm_printf_append(result,
                                                "%"PRIu64,
                                                (uint64_t)i);
+                } else if (element->vr == DCM_VR_AT) {
+                    // a ushort with half of a tag
+                    result = dcm_printf_append(result,
+                                               "%04x",
+                                               i);
                 } else {
                     result = dcm_printf_append(result, "%"PRId64, i);
                 }
@@ -1271,6 +1276,23 @@ char *dcm_element_value_to_string(const DcmElement *element)
         }
     }
 
+    // AT is a two-element ushort array holding a DICOM tag ... print the tag
+    // name if we can
+    if (element->vr == DCM_VR_AT && element->vm == 2) {
+        int64_t grp;
+        int64_t ele;
+        (void) dcm_element_get_value_integer(NULL, element, 0, &grp);
+        (void) dcm_element_get_value_integer(NULL, element, 1, &ele);
+
+        uint32_t tag = grp << 16 | ele;
+
+        const char *keyword = dcm_dict_keyword_from_tag(tag);
+
+        if (keyword) {
+            result = dcm_printf_append(result, " (%s)", keyword);
+        }
+    }
+
     return result;
 }
 

src/dicom-dict.c

@@ -54,7 +54,7 @@ struct _DcmVRTable_hash_entry {
 static const struct _DcmVRTable vr_table[] = {
     {DCM_VR_AE, "AE", DCM_VR_CLASS_STRING_MULTI,       0, DCM_CAPACITY_AE, 2},
     {DCM_VR_AS, "AS", DCM_VR_CLASS_STRING_SINGLE,      0, DCM_CAPACITY_AS, 2},
-    {DCM_VR_AT, "AT", DCM_VR_CLASS_STRING_MULTI,       0, DCM_CAPACITY_AT, 2},
+    {DCM_VR_AT, "AT", DCM_VR_CLASS_NUMERIC_INTEGER,    2, DCM_CAPACITY_AT, 2},
     {DCM_VR_CS, "CS", DCM_VR_CLASS_STRING_MULTI,       0, DCM_CAPACITY_CS, 2},
     {DCM_VR_DA, "DA", DCM_VR_CLASS_STRING_SINGLE,      0, DCM_CAPACITY_DA, 2},
     {DCM_VR_DS, "DS", DCM_VR_CLASS_STRING_MULTI,       0, DCM_CAPACITY_DS, 2},

src/dicom-file.c

@@ -1275,7 +1275,7 @@ static bool print_element_create(DcmError **error,
            filehandle->indent * 2,
            "                                   ",
            (tag & 0xffff0000) >> 16,
-           tag >> 16);
+           tag & 0xffff);
 
     if (dcm_is_public_tag(tag)) {
         printf("%s ", dcm_dict_keyword_from_tag(tag));

src/pdicom.h

@@ -67,6 +67,7 @@ int dcm_dict_vr_header_length(DcmVR vr);
 
 #define DCM_SWITCH_NUMERIC(VR, OPERATION) \
     switch (VR) { \
+        case DCM_VR_AT: OPERATION(uint16_t); break; \
         case DCM_VR_FL: OPERATION(float); break; \
         case DCM_VR_FD: OPERATION(double); break; \
         case DCM_VR_SL: OPERATION(int32_t); break; \