better detection of implicit mode in dcm-dump

automatically flip to implicit mode when printing dicoms

Author: jcupitt

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 * fix build with uthash \< 2.3.0 [bgilbert]
 * explicitly fail if macOS universal build is attempted [bgilbert]
+* better handling of implicit mode in dcm-dump [jcupitt]
 
 ## 1.1.0, 28/3/24
 

README.md

@@ -24,7 +24,7 @@ to add support](https://github.com/ImagingDataCommons/libdicom/issues).
 ## Building from source
 
 ```shell
-cd libdicom-1.0.0
+cd libdicom-1.1.0
 meson setup builddir --buildtype release
 meson compile -C builddir
 meson install -C builddir
@@ -108,7 +108,7 @@ This will print:
 $ ./read-frames.py sm_image.dcm
 opening libdicom ...
 init for libdicom ...
-libdicom version: 1.0.0
+libdicom version: 1.1.0
 frame 1 -> <10x10 pixels, 8 bits, 3 bands, RGB> 300 bytes
 frame 2 -> <10x10 pixels, 8 bits, 3 bands, RGB> 300 bytes
 frame 3 -> <10x10 pixels, 8 bits, 3 bands, RGB> 300 bytes

src/dicom-file.c

@@ -579,6 +579,29 @@ static DcmDataSet *dcm_filehandle_read_file_meta(DcmError **error,
 }
 
 
+static bool dcm_filehandle_set_transfer_syntax(DcmError **error,
+                                               DcmFilehandle *filehandle,
+                                               const char *transfer_syntax_uid)
+{
+    if (filehandle->transfer_syntax_uid) {
+        free(filehandle->transfer_syntax_uid);
+    }
+
+    filehandle->transfer_syntax_uid = dcm_strdup(error, transfer_syntax_uid);
+    if (filehandle->transfer_syntax_uid == NULL) {
+        return false;
+    }
+
+    if (strcmp(filehandle->transfer_syntax_uid, "1.2.840.10008.1.2") == 0) {
+        filehandle->implicit = true;
+    }
+
+    filehandle->desc.transfer_syntax_uid = filehandle->transfer_syntax_uid;
+
+    return true;
+}
+
+
 const DcmDataSet *dcm_filehandle_get_file_meta(DcmError **error,
                                                DcmFilehandle *filehandle)
 {
@@ -610,19 +633,13 @@ const DcmDataSet *dcm_filehandle_get_file_meta(DcmError **error,
             return NULL;
         }
 
-        filehandle->transfer_syntax_uid =
-            dcm_strdup(error, transfer_syntax_uid);
-        if (filehandle->transfer_syntax_uid == NULL) {
+        if (!dcm_filehandle_set_transfer_syntax(error,
+                                                filehandle,
+                                                transfer_syntax_uid)) {
             dcm_dataset_destroy(file_meta);
             return NULL;
         }
 
-        if (strcmp(filehandle->transfer_syntax_uid, "1.2.840.10008.1.2") == 0) {
-            filehandle->implicit = true;
-        }
-
-        filehandle->desc.transfer_syntax_uid = filehandle->transfer_syntax_uid;
-
         filehandle->file_meta = file_meta;
     } else {
         // move the read point to the start of the slide metadata
@@ -1503,7 +1520,15 @@ static bool print_element_create(DcmError **error,
 {
     DcmFilehandle *filehandle = (DcmFilehandle *) client;
 
-    USED(error);
+    // we must record the transfer syntax in the file meta since we need it
+    // to determine implicit/explicit encoding
+    if (tag == TAG_TRANSFER_SYNTAX_UID &&
+        vr == DCM_VR_UI &&
+        value &&
+        length > 10 &&
+        !dcm_filehandle_set_transfer_syntax(error, filehandle, value)) {
+        return false;
+    }
 
     printf("%*.*s(%04x,%04x) ",
            filehandle->indent * 2,
@@ -1615,8 +1640,7 @@ bool dcm_filehandle_print(DcmError **error,
     dcm_log_info("Read metadata");
     if (!dcm_parse_dataset(error,
                            filehandle->io,
-                           // FIXME we should check transfer syntax for this
-                           false,
+                           filehandle->implicit,
                            &parse,
                            filehandle)) {
         return false;

src/pdicom.h

@@ -43,6 +43,7 @@ typedef SSIZE_T ssize_t;
 #define MAX(A, B) ((A) > (B) ? (A) : (B))
 #define USED(x) (void)(x)
 
+#define TAG_TRANSFER_SYNTAX_UID                     0x00020010
 #define TAG_DIMENSION_INDEX_VALUES                  0x00209157
 #define TAG_REFERENCED_IMAGE_NAVIGATION_SEQUENCE    0x00480200
 #define TAG_PLANE_POSITION_SLIDE_SEQUENCE           0x0048021a