An image processing method using selected corner points and ridge lines to recognize triangular tissue of an organ pulled by forceps in a laparoscopic view has been developed. The proposed method could be used for semi-automatic control of a laparoscope robot. It makes use of a masking process based on the recognition of the forceps and clots, detection of corner points for a Delaunay diagram, detection of ridge lines oriented in the same direction, and recognition of the triangular working area. Triangles recognized in laparoscopic surgical videos using this method were similar to the correct triangles made by an endoscopic specialist.