fix(metadata): stop fabricating display metadata and add DICOM JSON converter
Replace the hand-built metadata subset in parseMeta with a VR-aware DICOM-to-DICOM-JSON converter. Window Center/Width, Rescale Intercept/Slope are only emitted when the source element exists; multi-values are preserved in source order. VOI/LUT, Presentation LUT and Pixel Padding tags are preserved and Pixel Data is excluded. - add src/dimse/dicomJson.ts (dictionary-aware converter) - rewrite src/dimse/parseMeta.ts to use the converter - add synthetic non-PHI DICOM writer and metadata tests - add npm test script (node:test + ts-node) and skipLibCheck
This commit is contained in:
padmanto
286
src/dimse/dicomJson.ts
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286
src/dimse/dicomJson.ts
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import dicomParser, { DataSet, Element, readFixedString } from 'dicom-parser';
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import { get_element } from '@iwharris/dicom-data-dictionary';
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/**
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* Minimal DICOM JSON model as defined by DICOM PS3.18 F.
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* See https://dicom.nema.org/medical/dicom/current/output/chtml/part18/sect_F.2.html
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*/
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export interface DicomJsonElement {
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vr: string;
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Value?: unknown[];
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InlineBinary?: string;
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BulkDataURI?: string;
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}
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export type DicomJsonDataSet = Record<string, DicomJsonElement>;
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export interface DicomJsonOptions {
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/**
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* Include private (odd group) data elements. Defaults to false to keep
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* responses small and to avoid leaking site-specific private data.
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*/
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includePrivate?: boolean;
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}
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/** String VRs that map to a JSON array of strings. */
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const STRING_VRS = new Set([
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'AE', 'AS', 'CS', 'DA', 'DT', 'LO', 'LT', 'SH', 'ST', 'TM', 'UC', 'UI', 'UR', 'UT',
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]);
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/** Numeric VRs and the byte-array parser reader used for each. */
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const NUMBER_VRS: Record<string, 'readUint16' | 'readInt16' | 'readUint32' | 'readInt32' | 'readFloat' | 'readDouble'> = {
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US: 'readUint16',
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SS: 'readInt16',
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UL: 'readUint32',
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SL: 'readInt32',
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FL: 'readFloat',
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FD: 'readDouble',
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};
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/** VRs whose payload is binary and must be encoded as InlineBinary/BulkDataURI. */
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const BINARY_VRS = new Set(['OB', 'OW', 'OF', 'OD', 'OL', 'OV', 'UN']);
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/** Pixel data and float pixel data are never part of the metadata response. */
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const EXCLUDED_TAGS = new Set(['7FE00010', '7FE00008', '7FE00009']);
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function formatKey(key: string): string {
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return key.replace(/^x/i, '').toUpperCase();
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}
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function groupOf(tag: string): number {
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return parseInt(tag.substring(0, 4), 16);
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}
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function isPrivateTag(tag: string): boolean {
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return (groupOf(tag) & 0x0001) === 1;
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}
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function isExcludedTag(tag: string): boolean {
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if (groupOf(tag) === 0x0002) {
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return true;
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}
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if (EXCLUDED_TAGS.has(tag)) {
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return true;
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}
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// Overlay data lives in groups 6000-60FF, element 3000.
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const group = groupOf(tag);
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if (group >= 0x6000 && group <= 0x60ff && tag.substring(4) === '3000') {
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return true;
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}
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return false;
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}
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function resolveAmbiguousVr(vr: string, tag: string, dataSet: DataSet): string {
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const options = vr.split(/\s+or\s+/i).map((v) => v.trim().toUpperCase());
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if (options.length === 1) {
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return options[0];
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}
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// Pixel Padding Value/Range Limit are US or SS depending on PixelRepresentation.
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if ((tag === '00280120' || tag === '00280121') && options.includes('US') && options.includes('SS')) {
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const pixelRepresentation = dataSet.uint16('x00280103');
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return pixelRepresentation === 1 ? 'SS' : 'US';
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}
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return options[0];
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}
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function resolveVr(element: Element, tag: string, dataSet: DataSet): string {
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let vr = element.vr;
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if (!vr) {
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const dictionaryEntry = get_element(tag);
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if (dictionaryEntry) {
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vr = dictionaryEntry.vr;
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}
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}
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vr = (vr || 'UN').toUpperCase();
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if (/\bor\b/i.test(vr)) {
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vr = resolveAmbiguousVr(vr, tag, dataSet);
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}
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return vr;
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}
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function byteArrayParserFor(element: Element, dataSet: DataSet) {
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return element.parser ?? dataSet.byteArrayParser;
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}
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function readBinary(dataSet: DataSet, element: Element): Buffer {
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const byteArray = dataSet.byteArray;
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if (Buffer.isBuffer(byteArray)) {
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return byteArray.subarray(element.dataOffset, element.dataOffset + element.length);
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}
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return Buffer.from(byteArray.buffer, byteArray.byteOffset + element.dataOffset, element.length);
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}
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function stripTrailingNul(value: string): string {
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let end = value.length;
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while (end > 0 && value.charCodeAt(end - 1) === 0) {
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end -= 1;
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}
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return value.slice(0, end);
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}
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function readStringValues(dataSet: DataSet, element: Element): string[] {
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const raw = readFixedString(dataSet.byteArray, element.dataOffset, element.length);
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const padded = stripTrailingNul(raw).replace(/ +$/g, '');
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if (padded.length === 0) {
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return [];
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}
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return padded.split('\\').map((value) => value.replace(/ +$/g, ''));
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}
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function parsePersonName(value: string): Record<string, string> {
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const [alphabetic, ideographic, phonetic] = value.split('=');
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const personName: Record<string, string> = {};
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if (alphabetic) {
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personName.Alphabetic = alphabetic;
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}
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if (ideographic) {
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personName.Ideographic = ideographic;
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}
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if (phonetic) {
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personName.Phonetic = phonetic;
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}
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return personName;
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}
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function readNumericValues(dataSet: DataSet, element: Element, vr: string): number[] {
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const readerName = NUMBER_VRS[vr];
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const reader = byteArrayParserFor(element, dataSet)[readerName];
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const width = readerName === 'readFloat' || readerName === 'readInt32' || readerName === 'readUint32'
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? 4
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: readerName === 'readDouble'
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? 8
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: 2;
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const count = Math.floor(element.length / width);
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const values: number[] = [];
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for (let i = 0; i < count; i += 1) {
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values.push(reader(dataSet.byteArray, element.dataOffset + i * width));
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}
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return values;
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}
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function readAttributeTags(dataSet: DataSet, element: Element): string[] {
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const parser = byteArrayParserFor(element, dataSet);
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const count = Math.floor(element.length / 4);
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const values: string[] = [];
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for (let i = 0; i < count; i += 1) {
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const offset = element.dataOffset + i * 4;
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const group = parser.readUint16(dataSet.byteArray, offset);
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const elementNumber = parser.readUint16(dataSet.byteArray, offset + 2);
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values.push(
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`${
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group.toString(16).padStart(4, '0')
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}${
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elementNumber.toString(16).padStart(4, '0')}`.toUpperCase(),
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);
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}
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return values;
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}
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function readDecimalStrings(dataSet: DataSet, element: Element): unknown[] {
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return readStringValues(dataSet, element).map((value) => {
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const parsed = Number(value);
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return Number.isFinite(parsed) ? parsed : value;
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});
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}
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function readIntegerStrings(dataSet: DataSet, element: Element): unknown[] {
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return readStringValues(dataSet, element).map((value) => {
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const parsed = Number.parseInt(value, 10);
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return Number.isFinite(parsed) ? parsed : value;
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});
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}
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function convertSequence(dataSet: DataSet, element: Element, options: DicomJsonOptions): DicomJsonElement {
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const items: DicomJsonDataSet[] = [];
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if (element.items) {
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for (const item of element.items) {
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if (item.dataSet) {
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items.push(convertDataSetToJson(item.dataSet, options));
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}
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}
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}
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return { vr: 'SQ', Value: items };
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}
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/**
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* Convert a parsed DICOM dataset into DICOM JSON (PS3.18 F).
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*
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* The conversion is VR aware: it uses the explicit VR stored on the element
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* when available and falls back to the DICOM data dictionary otherwise. Absent
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* attributes are never synthesized, so a source file without Window Center or
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* Rescale tags will not gain fabricated values.
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*/
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export function convertElementToJson(
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dataSet: DataSet,
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element: Element,
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options: DicomJsonOptions = {},
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): DicomJsonElement {
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const tag = formatKey(element.tag);
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const vr = resolveVr(element, tag, dataSet);
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if (vr === 'SQ') {
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return convertSequence(dataSet, element, options);
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}
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if (element.length === 0) {
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return { vr, Value: [] };
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}
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if (vr === 'PN') {
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return { vr, Value: readStringValues(dataSet, element).map(parsePersonName) };
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}
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if (vr === 'DS') {
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return { vr, Value: readDecimalStrings(dataSet, element) };
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}
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if (vr === 'IS') {
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return { vr, Value: readIntegerStrings(dataSet, element) };
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}
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if (vr === 'AT') {
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return { vr, Value: readAttributeTags(dataSet, element) };
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}
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if (NUMBER_VRS[vr]) {
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return { vr, Value: readNumericValues(dataSet, element, vr) };
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}
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if (STRING_VRS.has(vr)) {
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return { vr, Value: readStringValues(dataSet, element) };
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}
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if (BINARY_VRS.has(vr)) {
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return { vr, InlineBinary: readBinary(dataSet, element).toString('base64') };
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}
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// Unknown VR: fall back to an inline binary payload rather than guessing.
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return { vr, InlineBinary: readBinary(dataSet, element).toString('base64') };
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}
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export function convertDataSetToJson(
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dataSet: DataSet,
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options: DicomJsonOptions = {},
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): DicomJsonDataSet {
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const result: DicomJsonDataSet = {};
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for (const key of Object.keys(dataSet.elements)) {
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const element = dataSet.elements[key];
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const tag = formatKey(key);
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if (isExcludedTag(tag)) {
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continue;
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}
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if (!options.includePrivate && isPrivateTag(tag)) {
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continue;
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}
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result[tag] = convertElementToJson(dataSet, element, options);
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}
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return result;
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}
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export function parseDicomToJson(
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buffer: Buffer | Uint8Array,
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options: DicomJsonOptions = {},
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): DicomJsonDataSet {
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const dataSet = dicomParser.parseDicom(buffer);
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return convertDataSetToJson(dataSet, options);
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}
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