In an image forming apparatus, a processor acquires target image data representing a target image. The processor identifies as a first type pixel in the target image, and sets a target pixel from among peripheral pixels of the pixel identified as the first type pixel. The processor identifies the target pixel as a second type pixel in a case where the target pixel satisfies a specific condition. The processor generates processed image data by performing a replacement process in which a pixel value of the pixel identified as the first type pixel is replaced with a first value representing a first color and a pixel value of the pixel identified as the second type pixel is replaced with a second value representing a second color. The specific condition includes a condition that all specific pixels in a specific range match a specific pattern.