Source: dcmtk Version: 3.6.7-8+b1 Forwarded: https://support.dcmtk.org/redmine/issues/1079 Tags: upstream
dcm2json uses the method DcmJsonFormat::normalizeDecimalString() to normalize DICOM DS values before writing them as JSON. However, the method currently does not catch all cases where a legal DICOM DS value is not permitted in JSON. The JSON type number is defined in https://www.rfc-editor.org/rfc/rfc7159#section-6 as follows: number = [ minus ] int [ frac ] [ exp ] decimal-point = %x2E ; . digit1-9 = %x31-39 ; 1-9 e = %x65 / %x45 ; e E exp = e [ minus / plus ] 1*DIGIT frac = decimal-point 1*DIGIT int = zero / ( digit1-9 *DIGIT ) minus = %x2D ; - plus = %x2B ; + zero = %x30 ; 0 The definition of DICOM DS relies on the ANSI X3.9 standard, i.e. the specification of FORTRAN. The FORTRAN 'signed-real-literal-constant' is defined (in slightly simplified form) as: R709 kind-param is digit-string or scalar-int-constant-name R710 signed-digit-string is [ sign ] digit-string R711 digit-string is digit [ digit ] ... R712 sign is + or – R713 signed-real-literal-constant is [ sign ] real-literal-constant R714 real-literal-constant is significand [ exponent-letter exponent ] or digit-string exponent-letter exponent R715 significand is digit-string . [ digit-string ] or . digit-string R716 exponent-letter is E or D R717 exponent is signed-digit-string As a regular expression, DICOM DS values can thus be defined as [+-]?([0-9]+.[0-9]*|.?[0-9]+)(E[+-]?[0-9]+)? Differences between JSON number and DICOM DS are thus: JSON does not permit a leading '+' in the significand (i.e. "+1.0" is valid in DICOM but not in JSON) JSON does not permit leading zeroes in the significand (i.e. "0003" is valid in DICOM but not in JSON) JSON does not permit a leading '.' in the significand (i.e. ".5" is valid in DICOM but not in JSON) JSON does not permit a trailing '.' in the significand (i.e. "5." is valid in DICOM but not in JSON) DcmJsonFormat::normalizeDecimalString() currently accounts for differences 1 and 3, but not for 2 and 4. This should be fixed.
