An image-processing device includes a processor and a memory. The memory stores computer-readable instructions therein. The computer-readable instructions cause the image-processing device to identify a first region and a second region in a target image. The first region represents an encircling line for identifying a specific sub-region in the target image. The first region includes a plurality of pixels. The second region includes an inside region that is surrounded by the first region, and an outside region that is outside the first region. The image-processing device further performs changing a color value of a first target pixel included in the plurality of the pixels using a first internal pixel and a first external pixel.