Some clinical softwares refuse to perform some operations, when images are 'not

Some clinical softwares refuse to perform some operations, when images are 'not
native' (i.e. SOP Class UID -> [Secondary Capture Image Storage]), and
gdcm-written images fail.

At write time, gdcm has absolutely *no way* to guess if the image is 'native' or
not.
User is now allowed to specifiy what he wants to do (*he* knows, not gdcm !)
using the method :
void FileHelper::SetContentType (ImageContentType c);
(if you find a more significant name, feel free to tell me ...)
just before writting.
We have to deal with 4 *very* different cases :
-1) user created ex nihilo his own image and wants to write it as a Dicom image.
    c : USER_OWN_IMAGE
-2) user modified the pixels of an existing image, using mathematical operations.
   c : FILTERED_IMAGE
-3) user created a new image, using existing images (eg MIP, MPR, cartography image)
   c : CREATED_IMAGE
-4) user modified/added some tags *without processing* the pixels (anonymization..
   c : UNMODIFIED_PIXELS_IMAGE

'Image Type'                  (0x0008,0x0008)
Conversion Type               (0x0008,0x0064)
are set to values supposed to be constistant (hope so)
The reminding of the private method FileHelper::CheckMandatoryElements() remains
unimpared.