According to the documentation, ImageGear for C and C++ only supports reading and writing PDF documents with 1, 2, 8, 24 and 32 bit. http://help.accusoft.com/ImageGear/v19.1/Windows/DLL/webframe.html#IGDLL-08-012.html
It would be nice if ImageGear supports reading and writing PDF documents with 48 or 64-bit depth as well.
The color depth of images created by recent iPhones is often very high, and currently ImageGear cannot embed these images in PDF files.