Image processing method, three-dimensional position measuring method and image processing apparatus

An image processing apparatus comprising:

• an image inputting device that inputs a density image;
• an edge extracting device that extracts an edge pixel and the density gradient direction of the edge pixel from an edge in a density image inputted from the image inputting device;
• an edge position extracting device that retrieves the density gradient direction with reference to an edge pixel on the density image based on an extraction result of the edge extracting device and extracts an edge position in the unit of sub-pixel;
• a memory that stores a model image including a model of an object and data extracted from the model;
• a registering device that creates data that when an image including the model image is inputted from the image inputting device, relates a processing result of the edge extracting device and the edge position extracting device to the inputted image to each edge pixel extracted by the edge extracting device by an edge extracting device and registers in the memory;
• a similarity calculating device that when a processing object image including an object corresponding to the model is inputted from the image inputting device, scans a retrieval region of the same size as the model image in the processing object image in the unit of pixel so as to calculate a similarity between an image in the retrieval region and the model image for each scanning position;
• a corresponding edge extracting device that resets up the retrieval region at a position extracted based on the similarity calculated by the similarity calculating device and extracts an edge pixel corresponding to an edge pixel in the model image whose edge position is registered in the memory based on a processing result of the edge extracting device in the retrieval region, and that extracts an edge position in the unit of sub-pixel by retrieving the density gradient direction of each extracted edge pixel based on each edge pixel;
• a deviation quantity calculating device that makes the edge position extracting device process an edge pixel extracted by the corresponding edge pixel extracting device and pixels in the neighborhood so as to calculate the quantity of deviation between an edge position in the unit of sub-pixel extracted from the processing and an edge position registered in the memory;
• and
• a position specifying device that corrects the setting position of the retrieval region with the quantity of deviation calculated by the deviation quantity calculating device so as to specify the setting position after a correction as a position of the object.