1. An image processing device comprising: a controller configured to perform: receiving image data representing an image, the image having a plurality of pixels, the image data having a plurality of pixel values corresponding to the plurality of pixels; specifying an edge pixel based on the image data, the edge pixel representing an edge; setting a target pixel and a reference pixel from among the plurality of pixels, the reference pixel being located out of the edge, the target pixel being located between the edge pixel and the reference pixel; determining whether a determination condition is satisfied for the target pixel, the determination condition indicating that a pixel value of the edge pixel, a pixel value of the target pixel, and a pixel value of the reference pixel monotonically increase in said order; setting a binary value of the target pixel to a first value without using a dither matrix when the determination condition is satisfied for the target pixel; and setting the binary value of the target pixel to one of the first value and a second value different from the first value by using the dither matrix when the determination condition is not satisfied for the target pixel.