The wear condition of the artillery pipe is decisive to ballistic performance of the artillery and its detection is important to the using

maintenance and life evaluation. There are two types wear on the inner surface

the one is called friction wear

which is caused by the friction between the bullet and pipe's inner surface

making the rifling edge became smoother and smoother

the another is called ablation wear

which is caused by the high temperature and pressure gas produced by the fire powder

resulting cavities and flaws on the inner surface. These two types wear exhibit different appearance and have different evaluation criterions

it's necessary to divide these two types wear and give a respective detection. In the image of the inner surface of artillery pipe

the property which tell apart the edge of the rifling and the edge of the flaw and cavity is its direction: the edge of the rifling has a certain direction and shows a character of anisotropy but the edge of the flaw and cavity has no certain direction and shows a character of general isotropy. So the degree of the direction can be employed to divide the two types edge and measure the two types wear. Base on this

the mathematic modes of the friction wear and scrape wear are established

the direction image operator and its relative algorithm is proposed and proved

which can divide and detect the ablation wear and scrape wear from the image

realizing the image detection of the artillery body pipe's wear degree.