Image analysis – Color image processing
Reexamination Certificate
1999-08-20
2003-03-25
Mancuso, Joseph (Department: 2623)
Image analysis
Color image processing
Reexamination Certificate
active
06539108
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing device that accepts color image data expressed with arrays of pixels and executes a logical operation.
2. Description of Related Art
Various images are processed in an image processing device that processes various image data transmitted from image creating devices such as a personal computer and the like, and expands them into image data expressed with arrays of pixels that can be printed by a printer. As an example, when a plurality of picture images are mapped to be overlapped, there is processing that interprets a logical operation code to specify a method of superposing a newly written image upon an original image, executes a logical operation according to the method specified in the logical operation code, and superposes the images. This type of logical operation is generally known as the ROP (Raster OPeration) processing.
Originally, this ROP processing was devised for display on a display device of a personal computer or the like, and pixel data for the logical operation is premised to be expressed with the RGB color space. However, printers in general employ the CMYK color space finally, which is different from the space that the ROP processing premises. The ROP processing cannot be performed correctly with the color space that is not primary-independent, such that the K color component is dependent upon the other color components C, M, Y, as the CMYK color space. Accordingly, the execution of the ROP processing to the pixels expressed with the CMYK color space will lead to a result different from the case of the execution to the pixels of the RGB color space.
In view of this, as a method for correctly executing the ROP processing, for example, the following one is known. First, the ROP processing is executed while the image data expressed with the RGB color space is expanded into the pixel data of the RGB color space as it is. And, after the image data in one page is all expanded into the pixel data and the ROP processing is completed, the pixels for one page are converted all together into the CMYK color space. But, this method requires the color conversion of the pixel data expressed with the RGB color space into the pixel data of the CMYK color space all in a pixel unit. As a result, it requires a great amount of time for the color conversion. Moreover, the method will necessarily apply uniform color conversion to the image data, regardless of the types of the image data that the original plotting command indicates. Therefore, it is impossible to select color conversion parameters suited to the types of the image data, which induces the problem of picture quality.
In contrast to this method, the image processing device disclosed, for example, in the Japanese Published Unexamined Patent Application No. Hei 10-51651 employs a method that applies the ROP processing after converting the image data once expanded into the pixel data of the CMYK color space into the CMY color space only for the part that requires the ROP processing, and thereafter converts only the part converted into the CMY color space again into the CMYK color space. According to this method, a higher-speed processing can be expected in comparison to the above-mentioned method that once expands the image data into the pixel data of the RGB color space, and converts all the expanded pixel data into the CMYK color space. Also, this method enables a correct ROP processing, compared to the case of processing the pixel data of the CMYK color space as it is.
FIG. 6
is a flowchart to illustrate one operation example in the conventional image processing device. In this case, as described in the aforementioned document, the objects converted into the CMYK color space are checked to see whether the objects each need the ROP processing, and only when necessary, converted into the CMY color space to have the ROP processing applied, and thereafter again converted into the CMYK color space. As mentioned above, since the ROP processing cannot be correctly executed with the color space that is not primary-independent as the CMYK color space, the objects are converted once into the CMYK color space to have the ROP processing applied.
Incidentally, the objects may be converted once into the RGB color space from the CMYK color space to have the ROP processing applied. And, specially in this case, the flow of the processing is illustrated which plots to input the logical operation code indicating what kind of logical operation is executed with the color values of the CMYK color space at the position of a point (X, Y) in the coordinate system that assumes the horizontal direction and the vertical direction of the image for one page as X axis and Y axis, respectively.
At step S
51
, the coordinate, color values, and logical operation code of plotting data are inputted. The coordinate is substituted for the variables X and Y, the color values for the variable P, and the logical operation code for the variable C. If there is not specification of the logical operation code, a code indicating “having no specification” is substituted for the variable C.
At step S
52
, the judgment is made as to whether the ROP processing is necessary. This judgment checks whether the variable C is the code indicating “having no specification”. If the ROP processing is judged necessary, the process moves to step S
54
. And, if it is judged not necessary, the process moves to step S
53
, where the inputted color data of the CMYK color space stored in the variable P is stored as it is in the area including the position specified by the values of the variables X and Y.
If the ROP processing is necessary, first at step S
54
, a destination information is acquired. That is, the color data of the CMYK color space is loaded from the area including the position specified by the values of the variables X and Y, and substituted for the variable Q.
Next, at step S
55
, the color conversion from the CMYK color space into the CMY color space is executed. That is, the values of the variable P representing the color data of the CMYK color space inputted at step S
51
are converted into the color data of the CMY color space, and overwritten on the variable P and substituted for it. In the same manner, the values of the variable Q representing the color data of the CMYK color space in the destination information acquired at step S
54
are converted into the color data of the CMY color space, and overwritten on the variable Q and substituted for it.
And, at step S
56
, the ROP processing is executed. First, the type of an actual operation is determined from the values of the variable C representing the logical operation code. The logical operation determined as above is executed between the color components of the variable P representing the color data of the CMY color space in the input data and the variable Q representing the color data of the CMY color space in the destination information. The result is overwritten on the variable P and substituted for it.
At step S
57
, the color data of the CMY color space stored in the variable P being an operation result is converted into the color data of the CMYK color space, and overwritten on the variable P to be substituted for it. And, at step S
53
, the color data of the CMYK color space stored in the variable P is stored in the area including the position specified by the values of the variables X and Y. Thus, the ROP processing to the input data is terminated.
FIG. 7
is a chart to explain a concrete example of the images before and after the processing in one operational example of the conventional image processing device. The logical operation of AND is made between the bit map image having the character shape ‘A’ shown in FIG.
7
A and the background image shown in FIG.
7
B. The bit map image expressing ‘A’ shown in
FIG. 7A
is a rectangular bit map image, and the character part of ‘A’ is expressed with a color a and the background part is expressed with a color b. The color a is a color such that all
Kobayashi Kunihiko
Kunimasa Takeshi
Sekine Hiroshi
Shibata Fumihiko
Fuji 'Xerox Co., Ltd.
Le Brian
Mancuso Joseph
Morgan & Lewis & Bockius, LLP
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