METHOD OF AND APPARATUS FOR EXTRACTING IMAGE DATA

A method for extracting partial run-length data comprises the steps of: reading out total run-length data from a first memory in order of scanning; generating index data which indicates the relationship between the address of the first memory assigned to run-length data representing a first run of each scanning line and the subscanning coordinate of each scanning line; extracting partial run-length data representing the specified partial image out of the total run-length data from the first memory while referring to the index data corresponding to a range of the subscanning coordinate of the partial image; and executing image processing on the partial run-length data extracted.