fix(data): UN VR setting during naturalization/denaturalization (#379)

* FIx UN vr denaturalization

* Update tests

* Revert saving UN vr in _vrMap

* Add parsing from UN to dictionary vr

* Remove parseUnknownVr flag

* FIx test for UN vr

* Fix space

* Fix UN vr test formatting

src/DicomMessage.js

@@ -318,7 +318,19 @@ class DicomMessage {
             vr = ValueRepresentation.createByTypeString(vrType);
         } else {
             vrType = stream.readVR();
-            vr = ValueRepresentation.createByTypeString(vrType);
+
+            if (
+                vrType === "UN" &&
+                DicomMessage.lookupTag(tag) &&
+                DicomMessage.lookupTag(tag).vr
+            ) {
+                vrType = DicomMessage.lookupTag(tag).vr;
+
+                vr = ValueRepresentation.parseUnknownVr(vrType);
+            } else {
+                vr = ValueRepresentation.createByTypeString(vrType);
+            }
+
             if (vr.isExplicit()) {
                 stream.increment(2);
                 length = stream.readUint32();

src/ValueRepresentation.js

@@ -273,6 +273,10 @@ class ValueRepresentation {
         }
         return vr;
     }
+
+    static parseUnknownVr(type) {
+        return new ParsedUnknownValue(type);
+    }
 }
 
 class AsciiStringRepresentation extends ValueRepresentation {
@@ -1213,6 +1217,49 @@ class UnknownValue extends BinaryRepresentation {
     }
 }
 
+class ParsedUnknownValue extends BinaryRepresentation {
+    constructor(vr) {
+        super(vr);
+        this.maxLength = null;
+        this.padByte = 0;
+        this.noMultiple = true;
+        this._isBinary = true;
+        this._allowMultiple = false;
+        this._isExplicit = true;
+    }
+
+    read(stream, length, syntax) {
+        const arrayBuffer = this.readBytes(stream, length, syntax)[0];
+        const streamFromBuffer = new ReadBufferStream(arrayBuffer, true);
+        const vr = ValueRepresentation.createByTypeString(this.type);
+
+        var values = [];
+        if (vr.isBinary() && length > vr.maxLength && !vr.noMultiple) {
+            var times = length / vr.maxLength,
+                i = 0;
+            while (i++ < times) {
+                values.push(vr.read(streamFromBuffer, vr.maxLength, syntax));
+            }
+        } else {
+            var val = vr.read(streamFromBuffer, length, syntax);
+            if (!vr.isBinary() && singleVRs.indexOf(vr.type) == -1) {
+                values = val;
+                if (typeof val === "string") {
+                    values = val.split(String.fromCharCode(VM_DELIMITER));
+                }
+            } else if (vr.type == "SQ") {
+                values = val;
+            } else if (vr.type == "OW" || vr.type == "OB") {
+                values = val;
+            } else {
+                Array.isArray(val) ? (values = val) : values.push(val);
+            }
+        }
+
+        return values;
+    }
+}
+
 class OtherWordString extends BinaryRepresentation {
     constructor() {
         super("OW");

test/data.test.js

@@ -1106,6 +1106,30 @@ describe("The same DICOM file loaded from both DCM and JSON", () => {
     });
 });
 
+describe("test_un_vr", () => {
+    it("Tag with UN vr should be parsed according VR in dictionary", async () => {
+        const expectedExposureIndex = 662;
+        const expectedDeviationIndex = -1.835;
+
+        const url = "https://github.com/dcmjs-org/data/releases/download/unknown-VR/sample-dicom-with-un-vr.dcm";
+        const dcmPath = await getTestDataset(url, "sample-dicom-with-un-vr.dcm");
+
+        const file = await promisify(fs.readFile)(dcmPath);
+        const dicomData = dcmjs.data.DicomMessage.readFile(file.buffer, {
+            ignoreErrors: false,
+            untilTag: null,
+            includeUntilTagValue: false,
+            noCopy: false,
+        });
+        const dataset = dcmjs.data.DicomMetaDictionary.naturalizeDataset(
+            dicomData.dict
+        );
+
+        expect(dataset.ExposureIndex).toEqual(expectedExposureIndex);
+        expect(dataset.DeviationIndex).toEqual(expectedDeviationIndex);
+    });
+});
+
 it.each([
     [1.0, "1"],
     [0.0, "0"],