My goal is open Dicom files and convert thes into cv::Mat to process them with Opencv. I have compiled dcmtk 3.6.3 on ubuntu 18.4.1 and tried to link it with Qt 5.11.1 with Qt Creator 4.6.2 but failed to do so. and for the main: #include and I got this errors: Answer The error indicates that the linker could not