1. An image processing apparatus comprising: circuitry configured to: generate a plurality of processed images by performing image processing on at least one of a plurality of input images, the image processing being out of image encoding processing; determine, as a reference image for encoding a processed image generated by the image processing on the input image, whether the input image corresponding to the processed image generated by the image processing being out of image encoding processing is to be used or another processed image generated by the image processing being out of image encoding processing is to be used, based on a parameter obtained from the image processing being out of image encoding processing; and encode the processed image by referring to a reference image according to a determination.