1. An image processing apparatus comprising: an image processing section configured to include a defect detection unit, a direction determination unit, and a defect correction unit, wherein the direction determination unit detects a gradient direction having a minimum pixel value gradient as a pixel value gradient direction in a pixel area including a target pixel, by using a weighted addition result of a plurality of types of gradient information calculated through a plurality of different gradient detection processes, wherein the defect detection unit calculates, based on an output image resolution of a plurality of output image resolutions, a corrected pixel value obtained by applying the pixel value gradient direction detected in the direction determination unit with respect to the target pixel found within the pixel area using weights in the weighted addition result determined according to the output image resolution, wherein the pixel section is configured to include a plurality of pixel groups, each of the pixel groups including at least two pixels, and wherein the image processing section including the defect detection unit, the direction determination unit, and the defect correction unit are each implemented via at least one processor.