A system including an interface for receiving inspection image data of an inspection image of an inspection object. The inspection image data includes information of an analyzed pixel of the inspected image and of reference pixels of the inspected image. The system further includes a memory and a processor device operatively coupled to the interface and the memory to obtain an inspected value representative of the analyzed pixel of the inspected image, and a reference value for each of the reference pixels of the inspected image. For each reference pixel, the processor devices calculates a difference between the reference value of a respective reference pixel and the inspected value of the analyzed pixel, computes a representative difference value based on the differences and determines a presence of a defect in the analyzed pixel based on the representative difference value.