Printing method of color video printer

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG.
1, a color video printer wherein a high-speed printing method is applied comprises a microcomputer 20 for controlling all the operations in the color video printer; a line memory 18 for storing gradation data to be read or written under control of the microcomputer 20; a gradation counter 19 responsive to the microcomputer 20 for counting a gradation number in the video printer.
Three primary colors Red, Green and Blue provided by a video RAM (not shown) are converted into three elementary color components Cyan, Magenta and Yellow to be used later, which components are put into a memory 12 together with various control data to control a thermal print head in the printer.
A comparator 14 compares the gradation data read out of the line memory 18 with the counted value of the gradation counter 19.
A data switching circuit 13, coupled to the memory 12 and the line memory 18, provides a part of the data retrieved from the memory 12 to the line memory or enables transmission of data from the line memory to the comparator.
A data driver 15 enables transmission of the output of the comparator 14 to either one of a first buffer 16 or a second buffer 17 in dependence upon an address provided from the line memory.
Both of the first and second buffers are to enable transmission of the output of the data driver is in synchronism with a clock, to a latch 21 respectively.
Upon reception of a latch signal (LTH), the latch 21 receives gradation data from the first and second buffers and latches the received data to a driver for driving a thermal head assembly upon reception of a strobe signal (STB).
FIG.
3 is an exemplary diagram showing that a given number of gradation is stored into a respective address location corresponding to each line of the line memory; and FIGS.
4a to 4e are timing diagrams illustrating various operative stages of FIG.
1.
FIG.
4a represents a data waveform to be stored into the first buffer 16.
FIG.
4b represents a data waveform to be stored into the second buffer 17