1. A computer implemented method for determining at least one parameter of an image process to be applied to a target image to form a transformed image, the method comprising the steps of: receiving the target image to be processed using the image process, the target image being associated with a salience map determined for the target image; receiving a content masking map associated with the target image, the content masking map comprising at least one metric corresponding to a degree of visual perceptibility of changes to the target image arising from the image transform being applied to the target image; combining the salience map and the content masking map to determine a distribution of a set of preference measures with respect to the image transform, at least one of the preference measures being associated with an intermediate preference with respect to two other preferences; and determining the at least one parameter of the image process in accordance with the determined distribution of the preference measures.