A main input interface receives input image data. Memory stores multiple segment data S4 that specify the on/off states of the multiple respective segments that form a segment character on an image frame. A sub input interface receives sub data S3 that specifies the segment character to be displayed. A segment decoder converts the segment character into a raster image based on the sub data S3 and the multiple segment data S4. An image processing circuit generates output image data S2 to be displayed on a display panel, based on at least one of the input image data S1 and the output data S5 of the segment decoder.