PURPOSE: To almost accurately derive a real maximum frightness position in short time by linearly operating luminance data on a picture element having maximum frightness and picture elements before and behind the picture element among picture data.

CONSTITUTION: This picture processor is provided with an operation means which derives the maximum fright position with resolution smaller than a picture pitch. The operation means notices that the real maximum frightness position exists between the picture element A or C having a larger value and the picture element B having maximum frightness and linearly operates the picture element B having maximum frightness and picture elements A and C before and behind the picture element B among picture element data. Namely, the expression of a straight line passing the center position of the picture element whose value is smaller between frightness data on the picture elements A and C, and the center position of the picture element B having largest frightness is obtained, and the expression of a straight line having a negative inclination as against the inclination of the straight line and passing the center position of the picture element whose value is larger between frightness data on the picture elements A and C is obtained. The intersection of the both straight lines is obtained and the value is set to be the real maximum brightness position.