The invention relates to an image processing apparatus (1) comprising an image providing unit (2) for providing a first image of an object and a second image of the same object and a filtering unit (3) which filters the first image depending on a first degree of similarity between image values of the first image and on a second degree of similarity between image values of the second image. This allows filtering the first image depending on the likeliness that image values belong to the same part of the object, for example, to tissue or to bone material of the object, if the object is a human being or an animal, even if due to noise the image values of one of the first image and the second image are disturbed, thereby improving, for example, an edge preserving property of the filtering procedure.