Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1997-10-29
2004-05-04
Garcia, Gabriel (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S002100, C358S521000
Reexamination Certificate
active
06731400
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a printer controller, especially to a printer controller for obtaining a high quality image.
As a technique for printing a full color image by using the four basic colors of C (Cyanic), Y (Yellow), M (Magenta) and K (Black), a technique called multivalued dither processing is known. In multivalued dither processing, the difference between the color density of each pixel in a pixel matrix and the value of a corresponding element in a dither matrix is expressed by a multiple-value number, and in accordance with the multiple-value number, an area ratio of each basic color in a print unit area corresponding to the pixel is determined. Finally, each basic color is printed in the unit area at each determined area ratio.
An example of the above-mentioned multivalued dither processing is disclosed in JP-B-50909/1993.
In the processing technique disclosed in JP-B-50909/1993, by using a dither matrix in which dither values of elements monotonously increase in the main scanning direction, a dot concentration type dither pattern is implemented, and the color gradation in the multivalued dither processing is stabilized.
Furthermore, as a method of printing a full color image by using a color laser printer, a method in which an area to be printed for a pixel is changed corresponding to a color density by combining a dither processing method and a pulse width modulation method, a so-called multi-level gradation printing method using a dither method, is known. For example, in an image processing apparatus which is disclosed in JP-A-1611977/1984, by preparing various sizes of dither matrixes and pulse width modulation means which can perform modulation of a plurality of pulse widths and pulse periods, and by changing a combination of one of the dither matrixes and one of the PNM means for each image page of papers according to the kind of information provided on the paper, that is, a paper only including characters, a paper only including pictures, a paper including characters and pictures, etc., the number of color gradations for each pixel is changed, and an optimal printing is implemented according to the kind of information provided on the paper.
Generally, since a color image is expressed by three kinds of color signals of multiple levels, namely, bit map data, a great amount of image data is employed to express even one image. For example, as a method which can efficiently store or transmit such a great amount of data, a data compression processing method, which is a so-called JPEG (Joint Photographic Expert Group) method is known (International Standards IPU-TT. 81 Recommendation).
However, in the above-mentioned method, since the data compression factor changes according to the contents of a picture, it is not possible to estimate the memory capacity necessary to store the compressed data of one page in advance. Therefore, since it is necessary to provide sufficient memory capacity by assuming the lowest data compression factor, the production cost of a printing system to which the above-mentioned method is applied is increased. Furthermore, since the data compression factor changes, the signal processing also becomes complicated.
On the other hand, the present inventors have devised a code processing method for color image information, as disclosed in JP-B-7688/1994, in which the data compression factor is kept constant. That is, in the code processing method for information of the three basic colors to express a color image, each block is composed of a plurality of pixels, and the pixels in each block are classified into two groups by using an average gradation level of the block as a threshold value for each basic color. Furthermore, an average color gradation level of each group for each basic color is obtained as an approximate color. In each block, the difference between the color density of each pixel and the approximate color of each of the two groups is obtained, and the approximate color of a group, which indicates a smaller difference, is assigned to the pixel.
Code processing in which image information of each block is expressed by the two approximate colors of groups and the assignment of the approximate coolers to each pixel, is executed. In the above-mentioned code processing, since the length of the data for expressing the image information for each block is constant, the compression factor of image data is fixed.
If the above-mentioned code processing method and a multivalued (e-level) dither processing are employed in a printer system in which, after the image data of one page is first stored in a memory, printing of the image data is started, since the difference between the color density of each pixel and the value of each element in a dither matrix is expressed by m bits necessary to express n-levels in the n-level dither processing, it is necessary to store data including information expressing total pixels of one page, each pixel also being expressed by color data of m bits for each of four colors (C, M, Y, K).
Furthermore, if the multivalued dither processing is executed in a host computer, and the processed image data is transferred to a memory in a printer, it is necessary to transmit pixel data of each page expressed by color data of m bits for each of four colors.
Therefore in accordance with the above-mentioned conventional multivalued dither processing method, if the bit number of each of the data processed by the method is increased, the number of gradation for expressing each pixel color is also increased, but this requires a large memory capacity and a long data transmission time. On the other hand, if the bit number of each of the data is decreased, the memory capacity and the data transmission time can be reduced, but the number of gradations for expressing each pixel color is decreased, which deteriorates the quality of the image.
Furthermore, in the above-mentioned method, wherein the data processing method is changed in units of a page, it has been proven that the quality of the pictures and characters in a page of data including both pictures and characters is lower than that in a page including only pictures or only characters. It is further troublesome when a user switches a combination of one of various dither matrixes and the pulse width gradation number in the purse width modulation for each page.
In a method disclosed in JP-A-76377/1991, edge discrimination processing is performed for each input image, and different two-level processings are executed for an edge region and for a region neighboring the edge region, respectively.
Moreover, in a method disclosed in JP-A-90680/1993, edge discrimination processing is performed for each input pixel. If a pixel is discriminated as an edge pixel, and the color density of the pixel is higher than those of neighboring pixels, a more highly stressed color density is assigned to the pixel. On the other hand, if the color density of the pixel is lower then those of neighboring pixels, a lower color density is assigned to the pixel. If a pixel is not discriminated as an edge pixel, a not-stressed color density is assigned to the pixel, and a two-level data processing is performed on data for the pixel.
Meanwhile, in the methods disclosed in JP-A-76377/1991 and JP-A-90680/1993, although a two-level data processing is performed, a multiple-level data processing is not performed.
Generally, since the amount of image data to be processed is massive, an efficient data compressing method is important to process image data efficiently and to reduce the production cost of a printer system. In a conventional image printing method, it is premised that image data processing is executed for each image frame t page), and that image data of a partial region in the frame can not be rewritten. In such a method, even if data of only one pixel is to be rewritten, all compressed data (image data) for one frame is read out from the memory, the compressed data is expanded, data of the single pixel is rewritten, the data is compressed, and all the data is again stor
Inuzuka Tatsuki
Joh Manabu
Nakamura Toshiaki
Antonelli Terry Stout & Kraus LLP
Garcia Gabriel
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