News Column

Patent Issued for Image Processing Apparatus and Program Therefor

February 20, 2014



By a News Reporter-Staff News Editor at Computer Weekly News -- A patent by the inventor Matsuhira, Masatoshi (Matsumoto, JP), filed on April 15, 2011, was published online on February 4, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8643907 is assigned to Seiko Epson Corporation (Tokyo, JP).

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates to an image processing apparatus and a program therefor.

"There has been proposed an image processing apparatus that, in a high-speed mode, decreases the number of grid cells in a look up table (LUT) used for color conversion is decreased, and then stores the LUT in a storage unit whose storage capacity is small and whose access speed is high, and, in a high-quality mode, increases the number of grid cells in the LUT, and then stores the LUT in a storage unit whose storage capacity is large and whose access speed is low (e.g., see JP-A-2009-21915).

"In the image processing apparatus disclosed in JP-A-2009-21915, one LUT is always used for one piece of image data although the number of grid cells in the LUT is adjusted. However, it is conceivable that color conversion is performed for one piece of image data using LUTs that differ among pixels. Such a case is not taken into consideration in JP-A-2009-21915. Here, storage units with high access speeds are high in cost, and therefore many of them have relatively small storage capacities. Accordingly, although an image processing apparatus may attempt to store a plurality of LUTs in a storage unit with a high access speed in the same way as with only one LUT, there is sometimes a lack of storage capacity."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "An advantage of some aspects of the invention is that, regardless of whether one LUT or two LUTs are used, the LUT or LUTs are stored in a storage unit whose access speed is high and whose storage capacity is relatively small.

"To attain the advantage mentioned above, the invention employs the following.

"An aspect of the invention provides an image processing apparatus including a first storage unit configured to store, as look up tables (LUTs) referred to for color conversion from a first color space to a second color space, a photograph LUT suitable for the color conversion of each photograph pixel that is each pixel in a region representing a photograph, and a text LUT suitable for the color conversion of each text pixel that is each pixel in a region representing text; a second storage unit whose access speed is higher than an access speed of the first storage unit; a use LUT determination unit configured to determine, for image data made up of a plurality of pixels and being an object of the color conversion, whether a use LUT to be used during the color conversion of the image data is the photograph LUT or the text LUT or both of the photograph LUT and the text LUT; and a storing unit. The storing unit is configured to: in a case where the use LUT is determined to be the photograph LUT, read out the photograph LUT from the first storage unit and store the photograph LUT in the second storage unit by using a number of first photograph grid cells so that a storage size of the photograph LUT does not exceed an amount of free space of the second storage unit; in a case where the use LUT is determined to be the text LUT, read out the text LUT from the first storage unit and store the text LUT in the second storage unit by using a number of first text grid cells so that a storage size of the text LUT does not exceed the amount of free space of the second storage unit; and in a case where the use LUT is determined to be both of the photograph LUT and the text LUT, store the photograph LUT and the text LUT in the second storage unit with at least one of processing of storing the photograph LUT in the second storage unit by using a number of second photograph grid cells less than the number of first photograph grid cells and processing of storing the text LUT in the second storage unit by using a number of second text grid cells less than the number of first text grid cells so that a total of storage sizes of the photograph LUT and the text LUT read out from the first storage unit does not exceed the amount of free space of the second storage unit.

"In the image processing apparatus, the first storage unit stores, as look up tables (LUTs) referred to for color conversion from the first color space to the second color space, the photograph LUT suitable for the color conversion of each photograph pixel that is each pixel in a region representing a photograph, and the text LUT suitable for the color conversion of each text pixel that is each pixel in a region representing text. Then, for image data made up of a plurality of pixels and being an object of the color conversion, it is determined whether the use LUT to be used during the color conversion of the image data is the photograph LUT or the text LUT or both of the photograph LUT and the text LUT. Thereafter, in the case where the use LUT is determined to be the photograph LUT, the photograph LUT is read out from the first storage unit, and the photograph LUT is stored in the second storage unit by using the number of first photograph grid cells so that the storage size of the photograph LUT does not exceed the amount of free space of the second storage unit whose access speed is higher than the access speed of the first storage unit. Also, in the case where the use LUT is determined to be the text LUT, the text LUT is read out from the first storage unit, and the text LUT is stored in the second storage unit by using the number of first text grid cells so that the storage size of the text LUT does not exceed the amount of free space of the second storage unit. Also, in the case where the use LUT is determined to be both of the photograph LUT and the text LUT, the photograph LUT and the text LUT are stored in the second storage unit with at least one of processing of storing the photograph LUT in the second storage unit by using the number of second photograph grid cells less than the number of first photograph grid cells and processing of storing the text LUT in the second storage unit by using the number of second text grid cells less than the number of first text grid cells so that the total of storage sizes of the photograph LUT and the text LUT read out from the first storage unit does not exceed the amount of free space of the second storage unit. Therefore, in the case of using either of the photograph LUT and the text LUT for the color conversion of image data, and in the case of using both of the photograph LUT and the text LUT, appropriately adjusting the number of grid cells allows an LUT or LUTs to be stored in the second storage unit of a high access speed. In other words, regardless of whether one LUT or two LUTs are used, the LUT or LUTs can be stored in a storage unit whose access speed is high and whose storage capacity is relatively small.

"In the case where the use LUT is determined to be both of the photograph LUT and the text LUT, the storing unit may be a unit configured to store the photograph LUT in the second storage unit by using the number of grid cells greater than the number of grid cells for the text LUT. In such a way, although there is a possibility that the color of a text pixel will have degradation in quality after color conversion, the color of a photograph pixel will have high quality after the color conversion, which enables the appearance of all the image data to be of high quality. This is because, in general, degradation of quality is more noticeable in photograph pixels than in text pixels.

"The image processing apparatus may further include a mode setting unit configured to set any processing mode out of a photograph mode suitable for the color conversion of image data including a photograph pixel and not including a text pixel, a text mode suitable for the color conversion of image data including a text pixel and not including a photograph pixel, and a mixed text-and-photograph mode suitable for the color conversion of image data including both a photograph pixel and a text pixel. The use LUT determination unit may be a unit configured to, in a case where the photograph mode is set, determine that the use LUT is to be the photograph LUT, in a case where the text mode is set, determine that the use LUT is to be the text LUT, and, in a case where the mixed text-and-photograph mode is set, determine that the use LUT is to be both of the photograph LUT and the text LUT. In such a way, the use LUT can be appropriately determined according to the processing mode.

"The use LUT determination unit may be a unit configured to determine whether the image data includes a photograph pixel and whether the image data includes a text pixel, and configured to, in a case where the image data includes the photograph pixel and does not include the text pixel, determine that the use LUT is to be the photograph LUT, in a case where the image data includes the text pixel and does not include the photograph pixel, determine that the use LUT is to be the text LUT, and in a case where the image data includes both of the photograph pixel and the text pixel, determine that the use LUT is to be both of the photograph LUT and the text LUT. In such a way, the use LUT can be appropriately determined according to the image data.

"In the image processing apparatus, printing of the image data is carried out after the color conversion. The image processing apparatus may further include a paper information acquisition unit configured to acquire paper information indicating whether a type of paper as an object of the printing is special paper suitable for printing of the photograph pixel, and a color conversion unit configured to, in a case where the storing unit stores either of the photograph LUT and the text LUT in the second storage unit, perform color conversion of each pixel of the image data using the stored LUT, and, in a case where the storing unit stores the photograph LUT and the text LUT in the second storage unit, perform color conversion of each photograph pixel of the image data using the stored photograph LUT and perform color conversion of each text pixel of the image data using the stored text LUT. The storing unit may be a unit configured to, in a case where the use LUT is determined to be both of the photograph LUT and the text LUT and where the paper information indicates that the type of paper is not the special paper, store the photograph LUT and the text LUT in the second storage unit with processing of storing the photograph LUT in the second storage unit by using the number of second photograph grid cells less than the number of first photograph grid cells so that the total of storage sizes of the photograph LUT and the text LUT read out from the first storage unit does not exceed the amount of free space of the second storage unit, and, in a case where the use LUT is determined to be both of the photograph LUT and the text LUT and where the paper information indicates that the type of paper is the special paper, read out the photograph LUT from the first storage unit and store the photograph LUT in the second storage unit by using the number of first photograph grid cells so that the storage size of the photograph LUT does not exceed the amount of free space of the second storage unit. In general, in the case of printing image data on special paper suitable for printing of photograph pixels, degradation of quality of color is more noticeable in photograph pixels than that in the case of printing on another type of paper. In addition, in the case of printing on special paper, a user often places special emphasis on the quality of color of a photograph pixel rather than that of a text pixel. Here, in cases where the use LUT is determined to be both of the photograph LUT and the text LUT, if the paper type of an object of the printing is special paper, instead of and without storing the text LUT in the second storage unit, the photograph LUT is stored in the second storage unit by using the number of grid cells greater than that in cases where the paper type is any paper other than special paper. As a result, color conversion of text pixels is performed using the photograph LUT, which is less suitable for the color conversion of text pixels than the text LUT. However, high quality of the color of a photograph pixel after color conversion is achieved, which enables the appearance of all the image data after printing to be of high quality.

"The first storage unit may be a unit configured to store a first photograph LUT in which a number of grid cells is the number of first photograph grid cells and a second photograph LUT in which the number of grid cells is the number of second photograph grid cells, as the photograph LUT, and store a first text LUT in which the number of grid cells is the number of first text grid cells and a second text LUT in which the number of grid cells is the number of second text grid cells, as the text LUT. The storing unit may be a unit configured to perform storing of the photograph LUT in the second storage unit by using the number of first photograph grid cells by reading out the first photograph LUT from the first storage unit and storing the first photograph LUT in the second storage unit, perform storing of the photograph LUT in the second storage unit by using the number of second photograph grid cells by reading out the second photograph LUT from the first storage unit and storing the second photograph LUT in the second storage unit, perform storing of the text LUT in the second storage unit by using the number of first text grid cells by reading out the first text LUT from the first storage unit and storing the first text LUT in the second storage unit, and perform storing of the text LUT in the second storage unit by using the number of second text grid cells by reading out the second text LUT from the first storage unit and storing the second text LUT in the second storage unit. In such a way, it is only necessary to read out an appropriate LUT of LUTs stored in advance in the first storage unit and store the LUT in the second storage unit. This eliminates the necessity for changing the number of grid cells of the LUT.

"Another aspect of the invention provides a program for causing a computer to function as any one of the foregoing image processing apparatuses. The program may be recorded on a computer-readable recording medium (e.g., a hard disk, a ROM, a FD, a CD or a DVD), may also be delivered from one computer to another via a transmission medium (a communication network such as the Internet or a LAN), and may further be exchanged in any other form. When the program is executed by a computer, the computer functions as the image processing apparatus according to any one of the foregoing aspect of the invention, and therefore the same advantage as the image processing apparatus according to the aspect of the invention can be obtained."

URL and more information on this patent, see: Matsuhira, Masatoshi. Image Processing Apparatus and Program Therefor. U.S. Patent Number 8643907, filed April 15, 2011, and published online on February 4, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=55&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2710&f=G&l=50&co1=AND&d=PTXT&s1=20140204.PD.&OS=ISD/20140204&RS=ISD/20140204

Keywords for this news article include: Seiko Epson Corporation.

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Source: Computer Weekly News


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