| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect the position of an edge present inside a prescribed image area by setting the average value of the respective average gradation values of a part inside an area where an object is displayed and a part inside the area where a background is displayed as a threshold. SOLUTION: The image area R defined by two coordinates P and Q is set from images stored in an image memory and gradation projection data F(x) inside the image area R are found by a gradation projection data extraction part. Then, the average gradation value LB of a prescribed area R11 set inside a background image R1 and the average gradation value LM of the prescribed area R21 set inside an object image R2 are found. The average value of the obtained average gradation values LB and LM, that is 1/2 of the sum of both, is calculated as the threshold S. Then, the position of the edge is extracted from the gradation projection data F(x) and the threshold S. Even when the gradation of the background image or the object image is dispersed or even when the gradation is rapidly changed by noise, the position of the edge is highly accurately detected. |
