Processing of nontrivial images is a difficult task performed throughout a set of ordered steps. Besides the basic functionality that a process must satisfy, quality of service goals are to be met. Images should be processed within a certain time and a certain quality should be attained. To manage image-processing tasks in the optimal way, the process goals must be defined explicitly and their fulfillment has be controlled. Modeling image-processing tasks with workflows would enable control of the fulfillment of goals. In addition, by introducing flexible semantics in the workflow, the process could be executed along optimal execution alternatives. In this paper, we propose an approach to model the class of image processing tasks with workflows that would, based on the extended semantics, allow for flexibility in the process execution toward optimal goals fulfillment.