Image processing apparatus, control method therefor, and storage medium

Abstract

An image processing apparatus that enables a demosaicing process to be accurately carried out on a color image signal. With respect to a color mosaic image signal related to each pixel generated by photoelectrical conversion of an optical image reflecting a subject image, an interpolation process is carried out in which signals of missing colors in the each pixel are interpolated using image signals related to pixels in predetermined directions around the each pixel. The interpolation process is carried out in each of a plurality of predetermined directions. Color image signals in the predetermined directions subjected to the interpolation process are evaluated, and based on an evaluation result, a color image signal to be outputted as an interpolation process result is generated. The color image signals in the respective predetermined directions subjected to the interpolation process are evaluated with respect to homogeneity and signal intensity.

What is claimed is: 
     
         1 . An image processing apparatus comprising:
 an interpolation unit adapted to carry out an interpolation process in which, with respect to a color mosaic image signal related to each pixel generated by photoelectrical conversion of an optical image reflecting a subject image, signals of missing colors in the each pixel are interpolated using image signals related to pixels in predetermined directions around the each pixel,   wherein said interpolation unit comprises:   a direction-by-direction interpolation unit that carries out the interpolation process in each of a plurality of predetermined directions;   an evaluation unit that evaluates color image signals in the predetermined directions subjected to the interpolation process by the direction-by-direction interpolation unit; and   a generation unit that generates a color image signal to be outputted as an interpolation process result based on a result of the evaluation by the evaluation unit,   wherein the evaluation unit evaluates the color image signals in the predetermined directions subjected to the interpolation process with respect to homogeneity and signal intensity, and   wherein the evaluation unit evaluates the signal intensity using a G signal, an R-G signal, and a B-G signal.   
     
     
         2 . An image processing apparatus according to  claim 1 , wherein the evaluation unit evaluates the homogeneity using dispersion degree. 
     
     
         3 . An image processing apparatus according to  claim 2 , wherein the evaluation unit evaluates the dispersion degree using a G signal, an R-G signal, and a B-G signal. 
     
     
         4 . An image processing apparatus according to  claim 1 , wherein based on evaluation values of the respective pixels evaluated in the predetermined directions by the evaluation unit, the generation unit calculates a combination ratio of the color image signals in the predetermined directions subjected to the interpolation process, and combines the color image signals in the predetermined directions at the combination ratio, thus generating a color image signal to be outputted as an interpolation process result. 
     
     
         5 . A control method for an image processing apparatus, comprising:
 an interpolation step of carrying out an interpolation process in which, with respect to a color mosaic image signal related to each pixel generated by photoelectrical conversion of an optical image reflecting a subject image, signals of missing colors in the each pixel are interpolated using image signals related to pixels in predetermined directions around the each pixel,   wherein said interpolation step comprises:   a direction-by-direction interpolation step of carrying out the interpolation process in each of a plurality of predetermined directions;   an evaluation step of evaluating color image signals in the predetermined directions subjected to the interpolation process in the direction-by-direction interpolation step; and   a generation step of generating a color image signal to be outputted as an interpolation process result based on a result of the evaluation in the evaluation step,   wherein in the evaluation step, the color image signals in the predetermined directions subjected to the interpolation process are evaluated with respect to homogeneity and signal intensity, and   wherein in the evaluation step, the signal intensity is evaluated using a G signal, an R-G signal, and a B-G signal.   
     
     
         6 . A storage medium storing a program for causing a computer to execute a control method for an image processing apparatus according to  claim 5 .