Facsimile and static presentation processing – Static presentation processing – Memory
Reexamination Certificate
1999-03-22
2002-05-07
Evans, Arthur G. (Department: 2622)
Facsimile and static presentation processing
Static presentation processing
Memory
C358S001900
Reexamination Certificate
active
06384930
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printer control technique for performing high-speed printing.
The present application is based on Japanese Patent Applications No. Hei. 10-77882 and Hei. 11-25764, which are incorporated herein by reference.
2. Description of the Related Art
A printer used with a computer system usually forms a pseudo-continuous tone image-which-visually appears to be a continuous tone, through use of a limited number of coloring agents, such as cyan, magenta, and yellow (CMY), or cyan, magenta, yellow, and black (CMYK), by printing or not printing a small point (dot) of each coloring agent at each pixel position on a sheet (and, in some types of printers, by changing dots so as to assume a plurality of different sizes). Accordingly, image data finally required by the printer usually comprise CMYK raster image data which represent whether or not a dot of each color of CMYK coloring agents is printed or not printed at each pixel position (in some types of printers, the CMYK raster image data further represent which of a plurality of dot sizes is designated). Such CMYK raster image data require a color component resolution of only two or so (but not too many) levels. Throughout the specification, such CMYK raster image data will be referred to as CMYK raster image data having a “low-value resolution.”
Original image data—which are prepared by means of an application in a host computer which issues a print instruction to the printer or are input from the outside—are usually represented by a host color system differing from a printer color system; typically an RGB color system. Further, the original image data are RGB data having a “high-value resolution”; for example, a color component of 256-level gray scale. The original image data may be low-level data (raster image data) represented by a set of pixel values in one case and may be high-value data represented by a graphic function or character codes in another case.
In a conventional print system, the processing for converting high-value resolution RGB data of the original image into final CMYK data of low-value resolution is performed by means of a printer driver which is made up of software installed in a host computer, or by means of imaging software installed in the printer. The processing comprises a “rasterization” step of converting high-level original image data into raster image data; a “color conversion” step of converting RGB-based pixel values into CMY-based or CMYK-based pixel values through use of a look-up table; and a “halftoning” step of converting pixel values of high-value resolution into pixel values of low-value resolution through use of error variance or dithering. Further, in order to improve picture quality, an ink-jet printer employs a so-called “interlace” printing technique or an “overlap” printing technique, according to which dots are printed in a sequence differing from that in which the pixels are arranged. Interleaving of pixel values in a rearranged sequence for the purpose of effecting interlace printing or overlap printing is also carried out through the conversion process set forth.
If a printer driver carries out the foregoing conversion operations, the operations will impose a burden on the central processing unit (CPU) of a host computer. Similarly, if a printer carries out the foregoing conversion operations, the operations will impose a burden on the CPU of the printer. These processing operations are time consuming and account for a large portion of print time. A laser printer aimed at high-speed operations has a high-performance CPU and performs the foregoing conversion operations at high speed. Such a high-performance CPU is a primary factor for driving the cost of a laser printer considerably high. In contrast, in an ink-jet printer aimed at attaining a low price, a host computer processes all these operations. Consequently, the ink-jet printer is considerably slower in print speed, and the host computer is occupied for a long period of time, which in turn causes a delay in other tasks to be processed by the host computer.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to realize high-speed printing through use of inexpensive equipment.
Another object of the present invention is to realize high-speed printing without imposing a heavy burden on a CPU of a host computer in an environment where a low-speed printer, such as a conventional ink-jet printer, is used.
Still another object of the present invention is to provide an inexpensive printer capable of performing printing operations at high speed.
According to the present invention, a hardware circuit specifically designed for controlling a printer is interposed between a host machine, such as a host computer, and a printer. The printer-control-only hardware circuit may be incorporated into the host machine, incorporated into the printer, or embodied in the form of external device connected between the host machine and the printer.
The printer-control-only hardware circuit comprises a command analysis circuit, an image data processing circuit, a memory control circuit, command buffer memory, data buffer memory, and a command generation circuit.
The command analysis circuit receives a control circuit command from the host machine, determines whether the thus-received control circuit command is a backend parameter setting command used for transmitting a backend parameter which is required for resetting the printer or a high-order raster image transmission command for transmitting high-order raster image data (e.g., RGB raster data having high-value resolution), and transmits the backend parameter to the memory control circuit or the high-order raster image to the image data processing circuit.
The image data processing circuit converts the high-order raster image data received from the command analysis circuit into low-order image data (e.g., CMYK raster data having low-value resolution) required by a printing mechanism of the printer and transmits the low-order image data to the memory control circuit. For example, in a preferred mode, the image data processing circuit has a halftoning circuit which converts full-color RGB raster image data into binary CMYK raster image data.
The memory control circuit temporarily stores into the command buffer memory the backend parameter received from the command analysis circuit and temporarily stores into the data buffer memory the low-order raster image data received from the image data processing circuit. Further, the memory control circuit reads the backend parameter from the command buffer memory, transmits the thus-read backend parameter to the command generation circuit, reads the low-order raster image data from the data buffer memory, and transmits the thus-read low-order raster image data to the command generation circuit.
The command generation circuit generates, from the backend parameter received from the memory control circuit, a printer command for use in resetting the printer, transmits the thus-generated printer command to the printer, generates, from the low-order raster image received from the memory control circuit, a printer command for use in transmitting the low-order raster image to the printer, and transmits the thus-generated printer command to the printer.
By use of the above-described printer-control-only hardware circuit, at least a portion of data processing, which is performed by the CPU of a conventional host machine or the CPU of the printer, is offloaded from the CPU and placed on the printer-control-only hardware circuit, thereby lessening the burden imposed on the CPU. Particularly, an inexpensive, low-performance CPU may be used as the CPU of the printer. In a preferred mode, processing involving a heavy load, such a color conversion operation or a halftoning operation, is offloaded from the CPU and placed on the printer-control-only hardware circuit, thereby significantly lessening the burden imposed on the hostmachine or the printer. Further, as a matter of c
Evans Arthur G.
Seiko Epson Corporation
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