IMAGE PROCESSING APPARATUS FOR ESTIMATING ACTION OF SUBJECT AND ADDING INFORMATION INDICATING THE ACTION OF THE SUBJECT TO AN IMAGE, METHOD FOR CONTROLLING THE SAME, AND STORAGE MEDIUM

An image processing apparatus acquires a plurality of pieces of image data sequentially outputted from an imager and, in accordance with reception of an image capturing instruction to capture a still image, specify as image data to be processed a plurality of pieces of image data in a period that includes a timing at which the still image is captured. The image processing apparatus, based on an action of a subject estimated using the image data to be processed, add information that indicates the action of the subject to data of the still image.