License plate accurate positioning method and device in free scene

The invention discloses a license plate accurate positioning method and device in a free scene. The method comprises the steps: carrying out connected domain analysis of a preset license plate image,reserving a marked connected domain meeting a preset contour condition, recording boundary points of the connected domain, and obtaining an upper boundary point set and a lower boundary point set; performing straight line fitting on the upper boundary point set and the lower boundary point set by adopting a preset least square method to obtain an upper boundary line segment and a lower boundary line segment; calculating boundary point coordinates of four corners of an area interception frame according to the upper boundary line segment and the lower boundary line segment; intercepting a license plate area image of the expanded original license plate image through an area interception frame; and performing coordinate fitting on the left and right boundaries of the license plate area image by adopting a preset CNN m