| 摘要 |
PURPOSE:To automatically extract lineaments with high accuracy by detecting a part whose gradation is changed linearly on a picture as a line segment of unit length depending on direction and making the sensitivity of detection dependant on direction so as to eliminate the effect due to the direction of sun ray irradiation. CONSTITUTION:A lateral skew conversion in 0 is applied to an original picture 21 to produce a skew picture 22. Succeedingly, the skew picture 22 is subject to vertical compression to obtain a line element picture 23, which is subject to lateral differentiation. This processing is applied to utilize the property that a point having a larger lateral gradation change on the line element picture shown a larger picture intensity and represents an edge at the position of a line element on the original picture. The result of processings above is subjected to threshold processing to output a binary coded picture. Then points isolated longitudinally are eliminated. Succeedingly, the picture is magnified vertically by (l) times and the skew conversion with an angle -0 is applied. The line element in the specific direction extracted through the processing is added one after another to the result of extraction in the other direction. |
