DICOM: wrong inversion for 16bit MONOCHROME1 images when WindowCenter is not set but RescaleIntercept is

[ballaminut]

If a DICOM image has:

• no value for DICOM attribute (0028,1050) WindowCenter
• a value for DICOM attribute (0028,1052) RescaleIntercept (both represented as decimal string), the value of the latter is assigned to the centerPixelValue variable, creating problems in inversion for 16bit images (line 415). In particular if RescaleIntercept is 0, all pixel values become negative.

IMHO this is due to the fall through (line 586) break; case PHOTOMETRIC_INTERPRETATION: case PIXEL_SPACING: case SLICE_SPACING: case RESCALE_INTERCEPT: case WINDOW_CENTER: [...] break; case RESCALE_SLOPE: addInfo(tag, in.readString(elementLength)); break;

causing the RescaleIntercept to be assigned to centerPixelValue; probably the intended fall through was: break; case WINDOW_CENTER: String winCenter = in.readString(elementLength); if (winCenter.trim().length() == 0) centerPixelValue = -1; else { try { centerPixelValue = new Double(winCenter).intValue(); } catch (NumberFormatException e) { centerPixelValue = -1; } } addInfo(tag, winCenter); break; case PHOTOMETRIC_INTERPRETATION: case PIXEL_SPACING: case SLICE_SPACING: case RESCALE_INTERCEPT: case RESCALE_SLOPE: addInfo(tag, in.readString(elementLength)); break;

(with -1 initial value for centerPixelValue and maxPixelRange)

[ballaminut]

This is a file to test the behavior

000_2560x3328x1_16bit_1.2.840.10008.1.2.dcm.zip

[melissalinkert]

Confirmed that this is still a problem in 6.8.0. The RescaleIntercept is not assigned to centerPixelValue, but the default value of centerPixelValue is 0 and won't be changed when WindowCenter is not present. Similarly, the default value of maxPixelRange is 0 and won't be changed when WindowWidth is not present.

We'll need to improve the inversion logic here as well as the case described in #3620. The relevant DICOM schema section is https://dicom.nema.org/medical/Dicom/current/output/chtml/part03/sect_C.11.2.html#sect_C.11.2.1.2