matlab中fspecial('motion',LEN,THETA)参数LEN和THETA的含义

H = FSPECIAL('motion',LEN,THETA) returns a filter to approximate, once
convolved with an image, the linear motion of a camera by LEN pixels,
with an angle of THETA degrees in a counter-clockwise direction. The
filter becomes a vector for horizontal and vertical motions. The
default LEN is 9, the default THETA is 0, which corresponds to a
horizontal motion of 9 pixels.