1. An image processing device configured to process original image data representing an original image including a plurality of pixels, the image processing device comprising: a processor; and a memory storing computer-readable instructions therein, the computer-readable instructions, when executed by the processor, causing the image processing device to perform: generating edge image data by using the original image data, the edge image data representing an edge image by edge strengths corresponding to the plurality of pixels; calculating characteristic values for a plurality of determination regions, wherein each of the plurality of determination regions corresponds to one of the characteristic values, represents a part of the edge image, and includes a plurality of pixels, the plurality of determination regions being different from one another, each of the characteristic values characterizing the edge strength of the corresponding determination region; and identifying a determination region as a nonuniform region when the characteristic value of the determination region satisfies a prescribed criterion, and the determination region as a uniform region when the characteristic value of the determination region does not satisfy the prescribed criterion.