Patent ID: 8284436

Claim:
An image data processing apparatus, comprising: a reader that reads image data included in an image file in read units of a specified data length from an external storage medium storing the image file; a storage that temporarily saves the image data read by the reader; and a data processor that makes a request for image data from the reader and applies a specified data processing to the image data given from the reader in response to the request; wherein the reader reads image data requested by the data processor from the storage and supplies them to the data processor and, if the image data requested by the data processor cannot be read from the storage, reads image data of a specified data length including the image data from the external storage medium and supplies them to the data processor, and the reader changes the read units according to a form of the request from the data processor, wherein the reader changes the data length of the read units according to the form of the request from the data processor, and the reader sets a different read unit depending on whether or not an order of the image data requested by the data processor coincides with an arrangement order of the image data in the external storage medium if the storage cannot save all the image data included in the image file.