In a color print system based on the conventional technology, when a color image is printed, color image data prepared on a host computer is generally based on three elementary colors of R, G and B, but color image data printed with a color printer is based on CMY inks (or toners), so that image processing such as CMY conversion or color correction is required. Also to obtain a pseudo full color image, sometimes it is required to lower a gradation of an input image to a lower one with an output grading capability of a printer engine.
As a color print system conventionally proposed, there are ones disclosed, for instance, Japanese Patent Laid-Open Publication No. HEI 8-123633 or Japanese Patent Laid-Open Publication No. HEI 8-186724.
Next description is made for the color print system disclosed in Japanese Patent Laid-Open Publication No. HEI 8-123663 with reference to FIG. 14 to FIG. 17.
FIG. 14 is a block diagram showing configuration of the color print system disclosed in Japanese Patent Laid-Open Publication No. HEI 8-123633.
The color print system shown in FIG. 14 comprises a host computer 5 for preparing image data, a color printer controller 6 for having image data printed by controlling a color printer engine 7, and a color printer engine 7 for printing the image data. Also the color printer controller 6 comprises a host I/F 61, a CPU 62, a ROM 63, a RAM 64, and an engine I/F 65 or the like. The color printer comprises the color printer controller 6 and the color printer engine 7.
Next a description is made for operations of the color print system shown in FIG. 14.
At first, in the host computer 5, color image data to be printed is prepared according to an input operation by a user. Also the color image data is expressed with color formats such as RGB or CMYK. Further there are cases where prepared color image data is for forms with different sizes, where the color image data can not always be accommodated in a sheet of form, or where a plurality of copies are to be prepared.
Next when an instruction for printing the prepared color image data is issued upon an input operation by the user on the host computer 5, the color image data is sent to software stored inside the host computer 5 and called as printer driver.
In the printer driver, to respond to a difference of configuration of a connected printer, the color image data is converted to data with a format which the color printer controller 6 can interpret, and the color image data is sent to the host I/F 61 inside the color printer controller 6. More specifically, in the printer driver, in a case of color image data, data specifying degrees of densities of R, G and B (or C, M, Y, K) in each of characters, graphics, or images to be printed is sent to the color printer controller 6.
In the color printer controller 6, when color image data is sent from the host computer 5, the host I/F 61 receives the color image data, and once stores the color image data in a receiving buffer inside the host I/F 61 (it should be noted that a receiving buffer may not be provided in the host I/F 61 and the RAM 64 may be used in place of a receiving buffer).
Then the CPU 62 develops the color image data stored in the receiving buffer in the RAM 64 as the image data similar to, for instance, a result of output after printing as shown in FIG. 15 according to a program (instruction code) stored in the ROM 63. In the example shown in FIG. 15, the characters of "ABC" are developed in the RAM 64. In this example, only text data is shown, but also graphic data or image data is similarly developed as an image to be printed. When received data is color image data, as a full-color expression is made by overlaying 4 colors of CMYK in a color printer engine such as that based on an electronic photographing system, also the color image data developed in the RAM 64 has image data areas for 4 colors (4 plains) each to store therein a density value for each color component.
Then the CPU 52 executes communications via the engine I/F 65 with the color printer engine 7 at a point of time when full-color image data for one page has been developed in the RAM 64, reports to the engine I/F 65 that development of the image has been finished, and outputs an instruction for start of printing to the color printer engine 7.
When the color printer engine 7 starts its operation, the engine I/F 65 executes a video DMA operation, and sends the color image data developed in the RAM 64 to the color printer to have the color image data printed.
It should be noted that, as 4 colors are generally superimposed in a color printer engine based on the electronic photographing system, at first an image for one color component (toner image) is formed on a photo-sensitive body, then the color image data for one color formed on the photo-sensitive body is transferred onto an intermediate transfer belt (also sometimes called intermediate transfer drum), then a color image data for the next color component is formed and transferred to the intermediate transfer belt, and thus color image data for 4 color components is formed and transferred to the intermediate belt, and the toner images are finally transferred onto printing paper. Namely, as fill-color printing is made possible by forming and transferring images 4 times, color image data having been subjected to a video DMA operation or developed in the RAM 64 is managed by each color component.
When a plurality of pages are to be printed, a printer driver in the host computer 1 at first sends full-color image data for a first one page to the host I/F 61 in the color printer controller 6, and then notices the host I/F 61 of an end of one page by sending code indicating that transfer of image data for one page is finished and transfer of image data for a new page starts. Then the printer driver sends color image data for the next one page to the color printer controllers and repeats the operation for the subsequent pages.
Next a description is made for a band system of transferring color image data for one page by dividing the color image data to a plurality of bands in the auxiliary scanning direction with reference to FIG. 16 and FIG. 17.
For instance, when the color image data as shown in FIG. 16 is transferred from the host computer 5 and is developed in the RAM 64 in the printer controller 6, as shown in FIG. 17, color image data for one page is divided by a printer driver in the host computer 5 to a plurality of bands 1 to N (N: integral number of 2 or more) in the auxiliary scanning direction, at first color image data in the band 1 is transferred (it should be noted that, in this example, as there is no color image data to be printed in the band 1, only a color image data end command is sent), and then color image data in the band 2 is transferred.
In this case, in the band 2, such information as coordinates, font, and color density (RGB or CMYK) inside the band of the text data of "A" is sent out. It should be noted that, although FIG. 16 shows a case where text data is sent, in a case of image data, coordinates of points where the image is adhered and color image data (densities of color of each pixel) is sent out, and in a case of graphic data, such information as coordinates of points where the graphic data is adhered, a form of the graphic data, and density of colors to be painted is sent out.
In FIG. 17, in a case of color image data spread over a plurality of bands (band 2 and band 3) such as a character of, for instance, "B", at first the color image data is developed as data in a band previously sent in the side of the color printer controller 6, and then is stored as color image data for the next band in a buffer. In the side of host computer 5, when sending out color image data in the next band, the transfer operation is executed by developing the color image data by means of issuing an instruction of placing the color image data in a latter half section of the previous band (The instruction of placing color image data for a latter half section of the character of "B" in the next band in a latter half section of the previous band is issued because it is necessary to specify top and bottom of each image when a plurality of images are superimposed to each other).
Color image data up to the band N is sent by repeating the operations as described above, and then the processing in the host computer 5 is finished. Then, in the color printer controller 6 having received a print instruction, the CPU 62 starts development of color image data in each band from those in the band 1, and this operation is successively repeated up to the color image data in the band N. In this case, however, the color image data may be compressed in the RAM 64 or in a full-bit map according to a system of the color printer controller 6.
In the color printer controller 6 based on the display list system, the color image data for each of the characters as shown in FIG. 16 is divided to display code for each character (text data, image data, and graphic data for each character), and the display code for each character is developed.
Next a description is made for the color printer system disclosed in Japanese Patent Laid-Open Publication No. HEI 8-186724.
The color print system disclosed in Japanese Patent Laid-Open Publication No. HEI 8-186724 comprises a host computer and a printer.
The host computer temporally stored color image data in a work memory, and supplies the stored lusterized data via a job-partition method deciding section to the printer driver. The printer driver has an edge emphasizing section, an expanding/compressing section, a color correcting section, a finalizing section, and an RGB to CMY conversion section, and converts the lusterized data to color image data for printer output suited to the printer.
These image processing sections (edge emphasizing section, expanding/compressing section, color correcting section, finalizing section, and RGB to CMY conversion section) are also provided in a printer.
The job-partition method deciding section decides partition of a job between a host computer and a printer according to an image type based on a result of preliminary measurement executed for each image type, so that a waiting time for image processing is reduced and also a time required for print processing is reduced.
Namely, the host computer and color printer controller have common image processing units respectively, and take partial charge of an job respectively according to a image type.
Further there has been developed a color printer in which a maximum form size of a form available in the printer is, for instance, A3, and when an image with a size of A4 is printed by several copies, an area of a photo-sensitive body and that of an intermediate transfer belt of a color electronic picture printer engine are divided to two portions each with a size of A4 form as shown in FIG. 18. With this color printer, when transferring color image data, as shown in FIG. 19, after color image data for K for a first page is printed, color image data for K for a second page is printed, and then an image for C for a first page, an image for C for a second page, and . . . an image for Y for a second page are successively transferred and printed to make the printing speed higher.
This color printer is based on the electronic photographing system, and when a maximum size of a form available in the printer is A3, it is required that the photo-sensitive body and intermediate transfer belt are always applicable for a form having a size of A3 or more, and for this reason even when a form having a size smaller than A3 such as a form of A4 is printed, the printing speed is the same as that employed when a form with a size of A3 is printed, so that two sheet of A4 forms can be printed within a time required for printing one sheet of A3 size.
In the example described above, the printing order is always in the order of K, C, M and Y, but the sequence is not always required to be in this order, and also in the example described above, it is assumed that the maximum form size is A3, but the maximum form size is not always required to be A3, so that the number of sheets of form printed within a time required for printing a form with a size of A3 is not always limited to two sheets.
In the color print systems based on the conventional technology as described above, CMYK or RGB color information is sent in batch as color image data from a host computer to a color printer controller, so that, when a plurality of copies are to be made, printing of a first page will disadvantageously be delayed.
More specifically, in a case of a color printer engine based on a high speed electronic photographing system, in spite of the fact that a time of around 4 seconds is required for printing for one color component, the host computer 1 sends out color image data for all color components in batch to the color print controller, and the color printer controller 2 processes the RGB or CMYK color information sent thereto in batch, namely issues an instruction for start of printing to the color printer engine after color image data for all color components has been developed in a memory, so that printing of a first page will disadvantageously be delayed.
Similarly, even if the band processing is executed when sending color image data from a color printer driver to a color printer controller as described above, a print start instruction is outputted to the color printer engine after the final band within a page has been developed in a memory, so that the band processing and print processing can not be executed concurrently, and when a plurality of copies are to be printed, printing of a first page will disadvantageously be delayed.
Further, when a color printer engine enabling simultaneous printing of two sheets, at a point of time when color image data for two pages has been developed, the color printer controller is required to issue a print start instruction to the color printer engine, so that a printing speed for a first page when two sheets are printed in batch is slower as compared to that when one sheet is printed.