An external programming system for programming an implantable medical device includes a user display and a memory storing multiple intracardiac lead images. A detector is configured to sense the altered input light and to generate at least one electrical signal comprising information about a shift in the centroid of a spectral distribution of the altered input light relative to a centroid of the spectral distribution of the input light. The feature may include a marking on the lumen, a diameter of the lumen or a composition of the lumen. This ink composition can realize good image quality. A fourth subpixel output signal is determined from the fourth correction signal value and a fifth correction signal value determined from the expansion coefficient and the first to third subpixel input signals and output to the fourth subpixel.