A codec device is disposed in a display control device for instantly supplying decompressed image data to manipulating devices in the display control chip. Reference images are stored in compressed format after instantly compressed by the codec device. In addition, MSB portions and LSB portions are separately compressed for gaining higher compression ratio. Predication of the pixel value is also modified in variable length coding. On-chip line buffer is also applied with the instant compression mechanism. Fixed compression ratio is predetermined to actually downsize the chip design for the worst case.