An image processing apparatus for compositing multiple component images into a composite image is proposed. The image processing apparatus includes: a separating unit that separates a codestream corresponding to each one of the component images into a header portion and a data portion; a header processing unit that edits the separated header portion; and a codestream generation unit that generates a codestream corresponding to the composite image by combining the edited headers and the separated data portions. Each component codestream is generated by dividing the corresponding one of the component images into one or more rectangular regions, transforming pixel values of the divided one or more rectangular regions with discrete wavelet transform into transform coefficients, and compressing the transform coefficients.