Multiple Components in DICOM
DICOM standard allow storing of image with more than one components. As of today, only 1 or 3 components are considered valid DICOM SOP Class instances (for all IODs).
By design the itk::GDCMImageIO was designed and implemented so that an input YBR_FULL image would be loaded as such (no implicit conversion to RGB was done). The main reason for that is that ITK is a processing toolkit, so quantitative analysis is supposed to be done on the best possible pixel representation. Since conversion from integer YBR_FULL to integer RGB colorspace is a lossy operation (truncation in floating point representation), the conversion has never been implemented.
This behavior was considered ok, as long as the image was not directly loaded in viz application such as Slicer, where suddenly the image would appears with a weird color scheme.
The behavior for YBR_FULL vs RGB color model has been discussed and it seems consensus would be to convert to RGB always. Since DICOM, JPEG and TIFF can be somewhat relates for this matter, we should strive to keep the behavior consistent.
Current behavior of ITK 5.0:
|PALETTE_COLOR||X||RGB (??)||Converted to RGB||?Converted to RGB? (need to check compressed LUT)|
|YBR_FULL||ITK 81 enforce sub-sampling||??||YBR_FULL||??|
|YBR_ICT||ITU 81 does not support this colorspace||??||RGB||no J2K plugin|
|YBR_RCT||ITU 81 does not support this colorspace||??||RGB||no J2K plugin|
Desired behavior of ITK 5.0:
|PALETTE_COLOR||PALETTE_COLOR||PALETTE_COLOR||Converted to RGB||??|
|YBR_FULL||ITK 81 enforce sub-sampling||??||RGB||??|
|YBR_ICT||RGB||no J2K plugin|
|YBR_RCT||RGB||no J2K plugin|