1. An image processing device comprising: an image generator configured to generate a color image including a mark image and a normal image, wherein the image processing device is configured to output the mark image in a semi transparent manner, wherein a contrast of a boundary line of the mark image of a specific color component image of the color image is greater than a contrast of a boundary line of the normal image of the specific color component image of the color image, wherein the boundary line of the normal image is a boundary line distributed within a predetermined distance from the boundary line of the mark image, and the predetermined distance is greater than a half of a smaller one of a horizontal size or a vertical size of a cell at the boundary line of the mark image.