Now I introduced online access to the webcam settings. This should enable control of white balance and exposure time. However, the range of accessible settings seems to depend on the webcam type, I couldn't try out much with mine:-)
Also: introduced a clipping indicator for blue, green & red channel. Whenever the intensity goes >254 for at least one spectrum point , it is indicated for the respective colour channel.
Now, the interface looks already cluttered and not so well-thought... But hey, it is just a prototype with sub-standard UI :-)
IMPORTANT TIP: If you want to analyze an arbitray spectrum picture: replace the cam.bmp file in the program folder with your image, and try to connect to a webcam. If none present, it takes the cam.bmp file anyways for analysis...