1. An image processing device for detecting and suppressing shadows in a camera image of a surveilled scene, which camera image optionally shows static objects with static shadow regions and moving objects with dynamic shadow regions, the image processing device comprising: a processor, said process including a long-term recording module configured to generate a long-term reference image of the surveilled scene by evaluating a long-term observation of the surveilled scene; a mid-term recording module configured to generate a mid-term reference image of the surveilled scene by evaluating a mid-term observation of the surveilled scene; and a shadow-detecting module configured to process the camera image, using information technology, with the long-term reference image and the mid-term reference image in order to detect and suppress shadows; and means for filtering out static shadow regions, moving objects, and dynamic shadow regions out of the long-term reference image, so that the long-term reference image shows static objects in the surveilled scene.