1. An image processing apparatus having an image readout sensor with a plurality of pixels that optically reads out an image, and a driving unit that moves the image readout sensor, the image processing apparatus comprising: a control unit which controls the driving unit and the image readout sensor by causing the driving unit to move the image readout sensor such that each of the plurality of pixels reads out a chart that has a predetermined pattern; a calculation unit which calculates a feature amount of each of the plurality of pixels from the chart that has been read out through the control performed by said control unit; an analysis unit which analyses MTF characteristics of each of the plurality of pixels based on the feature amount calculated by said calculation unit; and a correction unit which corrects nonuniformity of the MTF characteristics of the plurality of pixels based on the results of the analysis performed by said analysis unit, wherein said calculation unit calculates, for each of the plurality of pixels, a maximum brightness variation as the feature amount.