1. An image processing method wherein a storage medium storing image data, key information appended to the image data, and image processing parameters attached to the image data and representing image processing to be effected on the image data is accessed to read the image data and the image processing parameters and the read image data are processed based on the image processing parameters, the image processing method comprising: a step of reading the key information when one or more image processing parameters attached to the image data are inappropriate for the image processing, a step of establishing, based on the read key information, new image processing parameters appropriate for the image processing, and a step of image-processing the image data based on the new image processing parameters.