Method of determining a feature of an image using an average of horizontal and vertical gradients

An image processor performed by a processor for processing a plurality of pixel values in an image data representing a two-dimensional image, the image processor comprising:

• an average gradient generator for
• defining a block representing a part of the two-dimensional image corresponding to a predetermined number of pixels in rows and columns, obtaining an average of a gradient of pixel value on the basis of the pixel values of adjacent pixels in the block along each of at least one of rows and at least one of columns, and
• generating a product of the average of the gradient pixel value along each of at least one of the rows and the average of the gradient pixel value along each of at least one of the columns;
• a gradient product generator for generating a double summation of the products of the gradient pixel values of each of the rows and the columns;
• and
• a feature amount generator for obtaining a feature amount of the block by performing a calculation between the double summation of the products and the product of the gradients comprising dividing the double summation of the products by the product of the gradients.

A non-transitory computer-readable storage medium storing a program for controlling a processor for executing a process of an image processing for processing a plurality of pixel values representing a two-dimensional image, the process comprising:

• defining a block representing a part of the two-dimensional image corresponding to a predetermined number of pixels in rows and columns;
• obtaining an average of a gradient of pixel value on the basis of the pixel values of adjacent pixels in the block along each of at least one of rows and at least one of columns;
• generating a product of the average of the gradient pixel value along each of at least one of the rows and the average of the gradient pixel value along each of at least one of the columns;
• generating a double summation of the products of the gradient pixel values of each of the rows and the columns;
• and
• obtaining a feature amount of the block by performing a calculation between the double summation of the products and the product of the gradients comprising dividing the double summation of the products by the product of the gradients.