1. An image processing apparatus comprising: an instruction unit adapted to designate one of a plurality of partial images and instruct execution of one of a plurality of processes for a classification process to determine whether the designated partial image contains a specific pattern; an execution unit adapted to perform, in accordance with the instruction from said instruction unit, the instructed process for the designated partial image using parameters for the classification process, including a threshold for determining whether to continue or terminate the classification process; and a determination unit adapted to determine, based on a result of execution by said execution unit, whether the classification process for the designated partial image has terminated, wherein when said determination unit determines that the classification process has not terminated for at least one of the plurality of partial images, said instruction unit designates one of the partial images for which the classification process are determined not to have terminated and outputs a re-instruction for execution of unexecuted one of the plurality of processes for the designated partial image, and in accordance with the re-instruction, said execution unit executes, using parameters different from the parameters previously used, the instructed process for the designated partial image.