METHOD FOR DISCRIMINATING DIRECTIVITY OF VECTOR

PURPOSE:To shorten the processing time for discrimination of directivities like the straightness, the orthogonality, or the parallelism between one vector and the other in a drawing recognition device. CONSTITUTION:Vectors are obtained, and their interior product value and their exterior product value are calculated. The former product value is the product between one vector and a component parallel with this vector of the other vector, and the latter is the product between one vector and a component perpendicular to this vector of the other vector. When directivities of vectors will be discriminated, they go straight if the angle obtained by connecting both vectors is within a prescribed range. Unless the interior product value is positive, they are not straight because the angle is larger than 90 deg. and directions are opposite. If the absolute value of the exterior product value is equal to or larger than the interior product value, they are not straight because the angle is larger than 45 deg.. Finally, it is discriminated that they are straight only when a ratio of the absolute value of the exterior product value to the interior product value is equal to or lower than a prescribed threshold.