1. An image storage device, comprising: addressing means for sequentially receiving image data defining pixels making up the image, and addressing the pixels as a grid of multi-pixel cells; first storage means for storing information concerning where in the grid cells having particular image characteristics are located; second storage means for storing information concerning position and nature of the particular image characteristics in the cells having the particular image characteristics; working memory means for storing only image data defining those pixels included in the cells having the particular image characteristics; and storage control means for specifying, as the image data defining the pixels making up the image is being received, those pixels whose image data is to be stored in said working memory means; wherein the image storage device stores only the image data defining those pixels included in the cells having the particular image characteristics, those pixels constituting less than all of the pixels making up the image.