metaData getModalityLUTOutputPixelRepresentation.ts

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50% Branches 8/16

50% Functions 1/2

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  /* eslint no-bitwise: 0 */
 
import type { DataSet } from 'dicom-parser';
 
function getMinStoredPixelValue(dataSet: DataSet) {
  const pixelRepresentation = dataSet.uint16('x00280103');
  const bitsStored = dataSet.uint16('x00280101');
 
  if (pixelRepresentation === 0) {
    return 0;
  }
 
  return -1 << (bitsStored - 1);
}
 
// 0 = unsigned / US, 1 = signed / SS
function getModalityLUTOutputPixelRepresentation(dataSet: DataSet) {
  // CT SOP Classes are always signed
  const sopClassUID = dataSet.string('x00080016');
 
  if (
    sopClassUID === '1.2.840.10008.5.1.4.1.1.2' ||
    sopClassUID === '1.2.840.10008.5.1.4.1.1.2.1'
  ) {
    return 1;
  }
 
  // if rescale intercept and rescale slope are present, pass the minimum stored
  // pixel value through them to see if we get a signed output range
  const rescaleIntercept = dataSet.floatString('x00281052');
  const rescaleSlope = dataSet.floatString('x00281053');
 
  Iif (rescaleIntercept !== undefined && rescaleSlope !== undefined) {
    const minStoredPixelValue = getMinStoredPixelValue(dataSet); //
    const minModalityLutValue =
      minStoredPixelValue * rescaleSlope + rescaleIntercept;
 
    if (minModalityLutValue < 0) {
      return 1;
    }
 
    return 0;
  }
 
  // Output of non linear modality lut is always unsigned
  Iif (dataSet.elements.x00283000 && dataSet.elements.x00283000.length > 0) {
    return 0;
  }
 
  // If no modality lut transform, output is same as pixel representation
  return dataSet.uint16('x00280103');
}
 
export default getModalityLUTOutputPixelRepresentation;