| 摘要 |
PURPOSE:To make it unnecessary to increase the size of a memory device even for multi-gradation data and to make it possible to similarly handle even for small-gradation data by said memory device, by arranging said memory device to be able to process data deeply in a gradation direction so as to memorize data in a form of gradation data and to compare said gradation data with a pattern of area gradation. CONSTITUTION:R, G, B image signals are selected by a selector 1, so that one of the signals R, G, B is selected and inputted to a (+) terminal of a comparator 3. Voltage of a threshold value is added to a (-) terminal of the comparator 3 by a D/A converter 2. An output signal from the comparator 3 and gradation data from a CPU 4 are added to an image memory device 5. A ROM 8 stores patterns of area gradation. At printing time, the value read from the memory device 5 is subjected to subtraction process in a subtracting circuit 6, and supplied to a thermal head 9 through a comparison circuit 7 where the value from the circuit 6 is compared with that of the ROM 8. Since the image memory device is constructed by gradation bits, the size of the memory device is not extraordinarily increased even when the data of many gradations are to be processed. |
