JP5811928B2 - Image processing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image processing apparatus and an image forming apparatus.

  Conventionally, when an image forming apparatus performs image processing such as color adjustment and gamma correction on input image data, each “pixel value before image processing” that can be taken by each pixel constituting the image data and “ Image processing is performed using a look-up table (LUT) in which each “pixel value after image processing” is associated with each other. That is, for example, when the pixel value A before image processing and the pixel value B after image processing are associated with each other, the pixel of the pixel value A included in the image data before image processing is a pixel in image processing. By referring to the LUT in which the value A and the pixel value B are associated with each other, the pixel value B is replaced.

However, the data amount of the LUT that associates all pixel values that can be taken by each pixel before image processing with the pixel value after image processing becomes enormous, and the memory capacity required to store the LUT also increases. End up.
Therefore, in order to reduce the amount of LUT data and the required memory capacity, some pixel values that can be taken by each pixel before image processing and the pixel values after image processing corresponding to the some pixel values are stored in the LUT. An image forming apparatus that stores and performs image processing on other pixel values by interpolation is known (for example, Patent Document 1).

JP 2009-214414 A

Incidentally, in recent years, with the improvement in productivity of image forming apparatuses, there has been a demand for higher speed in image processing before image formation.
Conventionally, as a general method for speeding up the image processing method, as shown in FIG. 8, a method of performing parallel processing in units of lines by taking a plurality of pixels constituting image data as units of lines in the horizontal direction has been adopted. It was.

  However, when parallel processing is performed in units of lines, a number of image processing units and memories corresponding to the number of parallel processing are required. Therefore, even if interpolation calculation is performed to reduce memory capacity, etc., the memory capacity required to support parallel processing will increase according to the number of parallel processing. It was impossible to achieve both capacity reduction.

  An object of the present invention is to provide an image processing apparatus and an image forming apparatus that can achieve both high-speed image processing and reduction in memory capacity.

  The invention according to claim 1 is an image processing apparatus that performs predetermined image processing on each of a plurality of pixels constituting an image, wherein a plurality of pixels included in a predetermined region of the image are converted into the plurality of pixels. Association means for associating with any of the groups smaller than the number, determination means for determining a representative value of each group based on the pixel value of the pixel associated with each group, and the pixel before the predetermined image processing A storage means for storing the pixel value after the predetermined image processing for the value, an acquisition means for acquiring the pixel value after the predetermined image processing corresponding to the representative value from the storage means, and an association with each group. And processing means for setting the pixel value of the obtained pixel to the pixel value after the predetermined image processing corresponding to the representative value of each group.

  A second aspect of the present invention is the image processing apparatus according to the first aspect, wherein the determining unit calculates an average value of the pixel values associated with each group by the association unit. It is a characteristic value.

  A third aspect of the present invention is the image processing apparatus according to the first or second aspect, further comprising generation means for generating range information indicating a range of pixel values corresponding to each group, wherein the association means A plurality of pixels included in the predetermined area are associated with each group based on a range of pixel values corresponding to each group.

The invention according to claim 4 is the image processing apparatus according to any one of claims 1 to 3, wherein the associating means sets the pixel values of the plurality of pixels included in the predetermined area. Based on this, the plurality of pixels are associated with each group.
A fifth aspect of the present invention is the image processing apparatus according to the fourth aspect, wherein the associating means sequentially sequentially for each pixel based on respective pixel values of a plurality of pixels included in the predetermined area. The plurality of pixels are associated with each group.
The invention according to claim 6 is the image processing apparatus according to claim 3, wherein the association unit includes a range of pixel values corresponding to each group, a pixel value of each of the plurality of pixels, The plurality of pixels are sequentially associated with each group on a pixel-by-pixel basis, and the generation unit determines a range of pixel values of the associated group after the association of one pixel by the association unit. The range information shown is updated.
A seventh aspect of the present invention is the image processing apparatus according to any one of the first to sixth aspects, wherein the predetermined image processing is color conversion processing from RGB to CMYK, and the storage means Stores the pixel values in the CMYK color space after the color conversion processing for the pixel values in the RGB color space before the color conversion processing.
The invention according to claim 8 is the image processing apparatus according to any one of claims 1 to 7, wherein the correspondence is performed until the predetermined image processing for all the pixels constituting the image is completed. The processing by the attaching means, the processing by the determining means, the processing by the acquiring means, and the processing by the processing means are repeated.
The invention according to claim 9 is the image processing apparatus according to any one of claims 1 to 8, wherein the plurality of pixels included in the predetermined region form a plurality of pixel lines, and each pixel line The number of pixels constituting the number and the number of the groups are equal.
A tenth aspect of the present invention is the image processing apparatus according to any one of the first to ninth aspects, wherein the association unit starts associating a plurality of pixels included in the predetermined area. The number of groups is set to one predetermined value.
The invention according to claim 11 is an image acquisition means for acquiring an image, an image processing means for performing predetermined image processing on each of a plurality of pixels constituting the image acquired by the image acquisition means, 11. An image forming apparatus comprising: an image forming unit that forms an image based on an image that has been subjected to predetermined image processing by the image processing unit, wherein the image processing unit is any one of claims 1 to 10. The image processing apparatus described above is included .

  According to the present invention, both speeding up of image processing and reduction in memory capacity can be achieved.

1 is a block diagram illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows an example of the circuit structure of an image process part. It is a block diagram which shows an example of a function structure of a representative value determination part. It is an image figure of matching with a representative value and each pixel in a predetermined field. It is a flowchart which shows an example of the flow of an image process. It is a flowchart which shows an example of the flow of a representative value acquisition process. It is a flowchart which shows an example of the flow of a matching process. It is an image figure of the image processing by the conventional parallel processing.

  Embodiments of the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.

FIG. 1 is a block diagram showing a main configuration of an image forming apparatus 1 according to an embodiment of the present invention.
The image forming apparatus 1 includes, for example, a communication unit 11, an image processing unit 12, an image forming unit 13, an operation display unit 14, a central control unit 15, and the like, and these units are connected by a bus 16.

The communication unit 11 includes, for example, a network interface card (NIC) or the like, and is connected to an external device such as a personal computer (PC) or a portable terminal connected via the communication network N by a predetermined communication protocol. Communicate.
The communication unit 11 receives a print job including an image formation instruction and an image data serving as a source of an image formed by the instruction from an external device via the communication network N.

  Note that the communication network N is, for example, a communication network constructed using an existing communication line, such as a LAN (Local Area Network), a WAN (Wide Area Network), a WiFi (Wireless Fidelity), or a Bluetooth (registered trademark). Various line forms such as NFC (Near Field Communication) can be applied. The form of the communication line of the communication network N may be wired, wireless, or a mixture of wired and wireless. The communication network N is, for example, a telephone line network, an ISDN line network, an optical fiber, a mobile communication network, a communication satellite line, a CATV line network, other dedicated lines and other communication line networks, and an Internet service for connecting them. A provider or the like may be included. The communication protocol adopted by the communication unit 11 is, for example, TCP / IP. However, the communication protocol is not limited to this example, and any type can be used as long as it is a protocol capable of mutual communication with an external device. It doesn't matter.

The image processing unit 12 performs image processing on the image data included in the print job. As image processing performed by the image processing unit 12, for example, color conversion processing for converting the color space (RGB or the like) of the image data into the color space (CMYK or the like) of the colorant of the image forming unit 13, or the color of the image Color adjustment processing to be adjusted, gamma correction processing, and the like can be mentioned, but this is an example and the present invention is not limited to this.
Details of the image processing by the image processing unit 12 will be described later.

The image forming unit 13 forms an image on a recording medium according to the image subjected to the image processing by the image processing unit 12.
Specifically, the image forming unit 13 includes, for example, a transport unit that transports a recording medium on which an image is formed, and a plurality of nozzles provided to face the recording surface of the recording medium transported by the transport unit. A recording head, an ink supply unit that supplies ink to the recording head, and the like, and ejects ink from a plurality of nozzles to a recording medium to form an image.

  The operation display unit 14 includes, for example, a touch panel type input display device, various input keys, switches, and the like, and receives input from the user. The central control unit 15 performs processing according to the input content from the operation display unit 14 and controls the operation of the image forming apparatus 1. The operation display unit 14 performs various display outputs related to the operation of the image forming apparatus 1 under the control of the central control unit 15.

The central control unit 15 controls the operation of each unit of the image forming apparatus 1.
Specifically, the central control unit 15 includes, for example, a CPU 15a, a RAM 15b, a ROM 15c, and the like. The CPU 15a reads programs, data, and the like corresponding to the processing contents from the ROM 15c and develops them in the RAM 15b, and executes various processes. Thus, the operation of each unit of the image forming apparatus 1 is controlled.

FIG. 2 is a diagram illustrating an example of a circuit configuration of the image processing unit 12.
The image processing unit 12 is a digital circuit constructed on an integrated circuit such as an FPGA (Field-Programmable Gate Array).
The image processing unit 12 includes a pixel value acquisition unit 121, a representative value determination unit 122, an LUT storage unit 123, a representative value conversion unit 124, a pixel value allocation unit 125, and the like.
Hereinafter, as an example of the image processing performed by the image processing unit 12, a description will be given of the processing content during the color conversion processing.

The pixel value acquisition unit 121 acquires each pixel value of a plurality of pixels included in a predetermined area of the image. Here, the pixel value is, for example, a value indicating the intensity or luminance of the pixel. Hereinafter, data indicating the intensity or luminance of a plurality of colors (for example, RGB) for each pixel constituting the pixel value processed in the present embodiment will be collectively referred to as “pixel data”.
Specifically, for example, as illustrated in FIG. 2, the pixel value acquisition unit 121 includes eight columns of flip-flop circuits in which eight flip-flop circuits (FFs) are provided in series. That is, the pixel value acquisition unit 121 has a storage area corresponding to a pixel area of 8 [pieces] × 8 [lines] = 64 [pixels]. The pixel value acquisition unit 121 performs pixel value acquisition processing 8 times to acquire pixel data of 1 [piece] × 8 [line] per time (1 [clk]) among a plurality of pixels constituting the image data ( 8 [clk]) is repeated to obtain pixel data of a pixel area of 8 [pieces] × 8 [lines] = 64 [pixels]. The pixel data of 1 [piece] × 8 [line] previously acquired by one pixel value acquisition process is sequentially moved to the right FF shown in FIG. By completing the pixel value acquisition process for the first time, the pixel value acquisition unit 121 holds pixel data of a pixel area of 8 [pieces] × 8 [lines] = 64 [pixels].
Here, the pixel area of 8 [pieces] × 8 [lines] acquired by the pixel value acquisition unit 121 is a predetermined area of the image.

  The representative value determining unit 122 determines the representative value of the pixel value corresponding to the number of groups smaller than the number of the plurality of pixels from each pixel data acquired by the pixel value acquiring unit 121. In the present embodiment, the representative value determining unit 122 determines eight representative values corresponding to eight groups from each pixel data of 64 [pixels] acquired by the pixel value acquiring unit 121. The eight representative values acquired by the representative value determining unit 122 of the present embodiment are various data values constituting pixel data, that is, values indicating the intensity or luminance of a plurality of colors (for example, RGB) for each pixel. Is a representative value.

Hereinafter, a method for selecting a representative value by the representative value determining unit 122 will be described.
FIG. 3 is a block diagram illustrating an example of a functional configuration of the representative value determining unit 122.
The representative value determining unit 122 includes, for example, a line switching unit 1001, a pixel switching unit 1002, a classification unit 1003, an updating unit 1004, a determining unit 1005, and a register 1010. Further, the classification unit 1003 includes a first determination unit 1006, a second determination unit 1007, a distance calculation unit 1008, and an integration unit 1009.

Hereinafter, each of the functional blocks included in the representative value determination unit 122 will be described in detail.
The register 1010 stores group information corresponding to eight representative values. Specifically, as illustrated in FIG. 3, the register 1010 includes first group information P1, second group information P2, third group information P3, fourth group information P4, and fifth group. Information P5, sixth group information P6, seventh group information P7, and eighth group information P8 are stored.
Each of the first group information to the eighth group information includes a reference value for distributing pixels associated with the representative value of each group, a statistical value for calculating the representative value, and a representative value of each group. And identification information for specifying the associated pixel. Each group information is assigned a first to eighth number (index).

In the present embodiment, the reference value of each group information is, for example, a diagonal point for specifying the corresponding color space (cuboid), that is, the intensity or luminance of the pixel associated with the representative value of each group. Includes maximum and minimum values.
Alternatively, the reference value of each group information includes, for example, the center point or barycentric point of the corresponding color space (cuboid).
The statistical value of each group information includes the cumulative intensity or luminance of the pixels associated with the representative value of each group.

  The representative value determining unit 122 repeats the association process for associating each pixel constituting one line with any of the eight group information items of the first group information P1 to the eighth group information P8. Then, the representative value determination unit 122 calculates a representative value corresponding to each group information based on the statistical value of each group information and the number of pixels associated with each group information. Details will be described below.

  The representative value determining unit 122 first reads the first group information P1 to the eighth group information from the register 1010. Note that at the start of the association process (or immediately after resetting), all group information is group information for which reference values have not yet been set, and the representative value determination unit 122 provides arguments and the like corresponding to the eight group information. Set up a framework for each group information.

  Next, the representative value determining unit 122, based on the first group information P1 to the eighth group information P8, and the pixel data of each pixel included in the line to be associated with the group information, Each pixel is associated with any of the first group information to the eighth group information. Hereinafter, a pixel (or pixel data) to be associated with group information is simply referred to as “target pixel (data)”.

  The line switching unit 1001 receives pixel data of each line constituting the pixel region from the pixel value acquisition unit 121 and inputs pixel data (line data) for one line to the pixel switching unit 1002. The line switching unit 1001 receives a line end notification from the pixel switching unit 1002 and inputs the next line data to the pixel switching unit 1002. When the line switching unit 1001 inputs all the line data acquired by the pixel value acquisition unit 121 to the classification unit 1003, the line switching unit 1001 sends a block end notification to the determination unit 1005.

The pixel switching unit 1002 receives line data from the line switching unit 1001 and inputs pixel data of one pixel to the classification unit 1003. Each time the pixel switching unit 1002 receives a pixel end notification from the update unit 1004, the pixel switching unit 1002 sequentially inputs the next pixel data to the classification unit 1003. When all the pixel data of the line data is input to the classification unit 1003, the pixel switching unit 1002 sends a line end notification to the line switching unit 1001.
In other words, the pixel switching unit 1002 manages the progress of the association process in units of pixels included in one line, and the line switching unit 1001 manages the progress of the association process in units of lines, and the target pixel data The target pixel data is sequentially switched to the next pixel data in accordance with the completion of any one of the associations with the group information.

  The first determination unit 1006 of the classification unit 1003 determines whether or not the pixel intensity included in the target pixel data is included in the reference values of the first group information P1 to the eighth group information P8. . Here, “included in the reference value” means, for example, the intensity (or luminance) of the pixel indicated by the maximum value and the minimum value of the intensity (or luminance) of the pixel included in the reference value. ) Is within the range.

  The second determination unit 1007 of the classification unit 1003 sets the reference value when the intensity of the pixel included in the target pixel data is not included in the reference values of the first group information to the eighth group information. It is determined whether there is group information that has not been set.

  When the intensity of the pixel included in the target pixel data is included in the reference values of the first group information to the eighth group information, the classification unit 1003 associates the pixel with the group information corresponding to the reference value. .

  The classification unit 1003 is a case where the intensity of the pixel included in the target pixel data is not included in the reference values of the first group information to the eighth group information, and the reference value is still set. If there is no group information, the target pixel is associated with group information for which no reference value has been set yet.

Therefore, after starting the association process (or immediately after resetting), the first target pixel is automatically associated with the first group information.
Then, when the intensity of the pixel included in the pixel data of the second target pixel is included in the reference value of the first group information (for example, the first target pixel and the second target) When the pixel data of the selected pixels are the same), the second target pixel is associated with the first group information. On the other hand, when the intensity of the pixel included in the pixel data of the second target pixel is not included in the reference value of the first group information, the reference value is not yet set in the second group information. Since it is group information, the second target pixel is associated with the second group information.
The same processing is repeated for the third and subsequent pixels, and at least the eighth pixel fits into the routine.

Here, the distance calculation unit 1008 of the classification unit 1003 does not include the pixel intensity included in the target pixel data in the reference values of the first group information to the eighth group information, and the reference value is still set. If there is no group information that has not been set, the distance (first distance) in the color space between the reference values of all the group information is calculated.
Further, the distance calculation unit 1008 calculates the distance (second distance) in the color space between the intensity of the target pixel and each of the reference values of all the group information.

In the case of the present embodiment, the first distance is a mutual distance in the color space when the reference values of two groups among the reference values of the eight group information are combined. Therefore, the distance calculation unit 1008 calculates 28 different distances as the first distance.
In the present embodiment, the second distance is a distance between the intensity of one target pixel and each of the reference values of the eight group information. Therefore, the distance calculation unit 1008 calculates eight different distances as the second distance.

  The integration unit 1009 of the classification unit 1003 compares the calculated first distance and the second distance, and if the shortest distance is included in the first distance, integrates two group information for the corresponding reference values. Then, one new group information is generated. In other words, the integration unit 1009 integrates two group information that is a combination with the smallest color difference.

  When integrating two pieces of group information, the integration unit 1009 merges group information with a small number (index) into group information with a large number. The representative value determination unit 122 performs an OR process on a “flag indicating which pixel is included”, which will be described later, on the group information after merging, adds up “cumulative CMYK intensity”, and sets the “number of pixels”. Add up. In addition, the representative value determination unit 122 compares the maximum and minimum RGB intensity values of the group information to be merged, and updates the maximum and minimum values of the group information after merging.

  When the integration unit 1009 generates two new pieces of group information by integrating the two pieces of group information, that is, when the existing eight pieces of group information are reduced to seven pieces of group information, the classification unit 1003 still has pixels. New group information not associated with is generated. That is, the classification unit 1003 newly generates eighth group information, and associates the target pixel with the new eighth group information.

  On the other hand, when the shortest distance is included in the second distance among the first distance and the second distance, the classification unit 1003 is specified as the shortest distance with the intensity of the target pixel. The target pixel is associated with the group information including the reference value.

  When the classification unit 1003 associates the pixel with the group information, the classification unit 1003 indicates identification information for specifying the pixel, the intensity of the pixel, and the number of the group information associated with the pixel (any one of 1 to 8). The information is transferred to the update unit 1004.

  The update unit 1004 receives identification information for identifying the pixel, the intensity of the pixel, and the number of group information associated with the pixel from the classification unit 1003, and the group information of the classification destination based on the intensity of the pixel Update the reference value and statistic value. When updating the reference value and the statistical value of the group information, the update unit 1004 sends a pixel end notification to the pixel switching unit 1002.

For example, the update unit 1004 updates the maximum value or the minimum value of the intensity of each color of the group information associated with the pixel based on the intensity of each color constituting the pixel data. Thereby, the range of the intensity of the pixel included in the reference value of the group information is increased.
Further, the update unit 1004 updates the total of the intensity of each color and the number of pixels of the group information associated with the pixel based on the intensity of each color constituting the pixel data.

The determination unit 1005 receives a block end notification from the line switching unit 1001 and represents the result of the association between the pixel and the group information based on the statistical values of the first group information P1 to the eighth group information P8. Information indicating the value and the pixel associated with each representative value is output.
That is, for example, the determination unit 1005 calculates, as a representative value, a value obtained by dividing the total of the intensities of the colors included in the statistical value of each group information by the number of pixels associated with each group information, and the representative value conversion unit 124. Output to. Further, the determination unit 1005 uses information indicating pixels associated with the group information that is a calculation source of each representative value calculated from each group information as information indicating pixels associated with each representative value. Output.

FIG. 4 is an image diagram of the correspondence between the representative value and each pixel in the predetermined area. The code | symbol described in each pixel which comprises the pixel area of 8 [piece] * 8 [line] shown in FIG. 4 shows the group information with which each pixel was matched.
As a result of the processing by the representative value determining unit 122, 64 [pixels] pixels included in the pixel area of 8 [pixels] × 8 [lines] have first group information P1 to P1th as shown in FIG. 8 associated with any one of the group information P8.
Therefore, the representative value determining unit 122 functions as an association unit that associates a plurality of pixels included in a predetermined area of the image with any of a group having a number smaller than the number of the plurality of pixels.
The representative value determining unit 122 functions as a determining unit that determines the representative value of each group based on the pixel value of the pixel associated with each group.

The LUT storage unit 123 is a memory that stores an LUT in which each pixel value before color conversion processing that can be taken by each pixel constituting image data is associated with each pixel value after color conversion processing.
Here, the LUT storage unit 123 functions as a storage unit that stores pixel values after predetermined image processing with respect to pixel values before predetermined image processing (for example, color conversion processing).

  In the present embodiment, the LUT stored in the LUT storage unit 123 is an LUT for which interpolation processing is assumed. In other words, the LUT stored in the LUT storage unit 123 is a partial pixel value (for example, a pixel value in the RGB color space) that can be taken by each pixel before the color conversion process and a color corresponding to the partial pixel value. The LUT is associated with pixel values after conversion processing (for example, pixel values in the CMYK color space).

The representative value conversion unit 124 performs color conversion processing of the representative value selected by the representative value determination unit 122.
Specifically, the representative value conversion unit 124 uses the pixel value indicated by the representative value as the pixel value before the color conversion process, and acquires the pixel value after the color conversion process corresponding to the pixel value. The representative value conversion unit 124 refers to the LUT stored in the LUT storage unit 123, performs an interpolation operation as necessary, performs a color conversion process on the pixel value indicated by the representative value, and a pixel value after the color conversion process To get.
Here, the representative value conversion unit 124 functions as an acquisition unit that acquires the pixel value after predetermined image processing (for example, color conversion processing) corresponding to the representative value from the LUT storage unit 123.

  The representative value conversion unit 124 according to the present embodiment includes eight groups of representative values selected by the representative value determination unit 122 based on 64 [pixels] acquired with one pixel value acquisition process by the pixel value acquisition unit 121. A color conversion process is performed on each of the above. That is, the representative value conversion unit 124 accesses the LUT storage unit 123 eight times for color conversion processing of each of the eight groups of representative values.

The pixel value assigning unit 125 obtains the pixel value acquired by the representative value conversion unit 124 for the pixel area configured by 64 [pixels] acquired by one pixel value acquiring process by the pixel value acquiring unit 121. That is, the pixel value subjected to the color conversion process is assigned to the representative value.
That is, the pixel value assigning unit 125 replaces the pixel value of the pixel associated with each group with a pixel value obtained by performing color conversion processing on the representative value of each group.

The pixel values assigned by the pixel value assigning unit 125, the pixel values of the respective pixels included in the pixel area configured by 64 [pixels] acquired by the pixel value acquiring unit 121 by the pixel value acquiring process eight times, The pixel value is obtained by performing color conversion processing on the representative value obtained from the group information in which each pixel is associated. The image processing unit 12 completes the color conversion processing for the predetermined area by the pixel value allocation by the pixel value allocation unit 125.
Here, the pixel value assigning unit 125 functions as a processing unit that sets the pixel value of the pixel associated with each group to a pixel value after predetermined image processing corresponding to the representative value of each group.

  In the color conversion process, the image processing unit 12 uses the pixel value acquisition unit 121, the representative value determination unit 122, the LUT storage unit 123, the representative value conversion unit 124, and the pixel value allocation unit 125 to include image data included in the print job. A predetermined region (for example, 8 [pieces] × 8 [line] pixel region) is sequentially cut out from the image and color conversion processing is performed. In addition, when the color conversion process for one predetermined region is completed, the image processing unit 12 resets and initializes various types of information included in the first group information P1 to the eighth group information P8. That is, the determination of the representative value and the management of the pixels associated with each representative value are performed individually for each predetermined area.

As shown in FIG. 2 and the above description, the pixel value acquisition unit 121 has eight flip-flop circuits connected in series corresponding to the eight pixels constituting each line, and one line of It takes 8 [clk] processing time to acquire the pixels.
Further, the representative value conversion unit 124 accesses the LUT storage unit 123 a number of times according to the number of groups (eight times) in order to obtain pixel values after color conversion processing corresponding to the representative values of eight groups. Processing time corresponding to the number of times, that is, processing time of 8 [clk] is consumed.
Here, since the processing time by the pixel value acquisition unit 121 and the processing time by the representative value conversion unit 124 are the same, the image processing unit 12 acquires the pixel value by the pixel value acquisition unit 121 and the representative value conversion unit. The conversion of the representative value by 124 can be performed in parallel, and pipeline processing on hardware can be realized.

In the above description, the color conversion process has been described as an example of the specific processing contents of the image processing unit 12, but the image processing unit 12 includes a step of individually referring to the pixel value and the like of each pixel. For various types of image processing, as in the color conversion processing described above, representative values in a predetermined area are determined, and pixel values after image processing corresponding to the respective representative values are acquired, and each pixel associated with each representative value By substituting the pixel values, the image processing is performed on each pixel in the predetermined area.
In other words, the image processing unit 12 stores an LUT corresponding to the type of image processing in the LUT 123, and switches various types of image processing by switching the LUT to be referred to according to the type of image processing performed on the image. It can be carried out.

Hereinafter, the flow of image processing by the image processing unit 12 will be described with reference to the flowcharts of FIGS.
First, the image processing unit 12 acquires the pixel value of each pixel corresponding to a predetermined pixel region by the pixel value acquisition unit 121 (step S1).
Next, the image processing unit 12 acquires a representative value by the representative value acquiring unit 122 (step S100). Here, the image processing unit 12 acquires a predetermined number (for example, eight) of representative values and information indicating correspondence between each representative value and each pixel constituting a predetermined pixel region.
Next, in the image processing unit 12, the representative value conversion unit 124 accesses the LUT storage unit 123 to acquire a pixel value (correction value) after image processing corresponding to the representative value (step S2).
Then, in the image processing unit 12, the pixel value assigning unit 125 performs image processing by setting the pixel value of the pixel associated with each representative value as the correction value of the associated representative value (step S3). .

Thereafter, the image processing unit 12 determines whether or not the image processing for all the pixel areas constituting the image data has been completed (step S4). Here, when it is determined that the image processing for all the pixel regions has not been completed (step S4: NO), the image processing unit 12 proceeds to the processing of step S1 and repeats the image processing.
On the other hand, when it is determined in step S4 that the image processing has been completed for all the pixel areas constituting the image data (step S4: YES), the image processing unit 12 ends the image processing.

  Hereinafter, the flow of the representative value acquisition process shown in step S100 will be described with reference to the flowcharts of FIGS.

  First, the representative value determining unit 122 functioning as the line switching unit 1001 prepares group information for distributing pixels in a target pixel region (step S101). More specifically, the representative value determining unit 122 reads the first group information P1 to the eighth group information P8 (temporary information) for the target block from the temporary save area of the register 1010, and registers 1010. Stored in the work area. Note that the temporary save area of the register 1010 and the work area of the register 1010 may be realized by different storage devices, or may be realized by different areas of the same storage device.

  The representative value determining unit 122 functioning as the classifying unit 1003 executes a process of associating the target line pixels (eight pixels) with the group information (step S200). The association process (step S200) will be described later.

  When the process of associating the 8 pixels of the target line is completed, the representative value determining unit 122 transfers data (first group information for the target pixel area to the next line) from the work area of the register 1010 to the next line. (Eighth group information) is read and the data is stored in the temporary save area of the register 1010 (step S102).

  More specifically, step S102 is a process for temporarily saving data in order to perform the process for the next line. After completing the association process of 8 pixels, the register 1010 displays the reference value, statistical value, and identification information for each group information, that is, “maximum and minimum values of RGB intensity” for each group information, and “RGB for each group information. As the data to be taken over to the processing of the next line, the “total number of intensity”, the “number of pixels associated with the group information” for each group information, and the group information number (index) associated with each pixel, The data is stored until the association process for each pixel in the next line is started.

  The representative value determining unit 122 determines whether or not there are more lines after the target lines in S102, S200, and S104 (step S103). The representative value determination unit 122 repeats the processing from step S101 when there are more lines after the target line in S102, S200, and S104 (step S103: YES).

  On the other hand, when there is no line after the target line in S102, S200, and S104 (step S103: NO), the representative value determining unit 122 sets all lines (for example, 8 lines, 64 lines) in a predetermined pixel area. It is determined whether or not the association between each pixel of pixel) and any of the group information is completed (step S104). The representative value determination unit 122 repeats the processing from step S101 when the association between each pixel of all lines and any of the group information is not completed (step S104: NO).

  On the other hand, when the association between each pixel for all lines and any of the group information is completed (step S104: YES), the representative value determining unit 122 calculates the total of the intensities of the respective colors included in the statistical value of each group information. The value divided by the number of pixels associated with each group information is calculated and output as a representative value, and the pixel associated with the group information from which each representative value calculated from each group information is calculated Is output as information indicating the pixel associated with each representative value (step S105).

  Hereinafter, the process of associating the target pixel with the group information shown in step S200 will be described with reference to the flowchart of FIG.

  First, the representative value determination unit 122 functioning as the classification unit 1003 determines whether or not the intensity of the pixel included in the target pixel data is included in the reference values of the first group information to the eighth group information. (Step S201).

When the intensity of the pixel included in the target pixel data is included in the reference values of the first group information to the eighth group information (step S201: YES), the representative value determining unit 122 sets the pixel as the reference value. Is associated with the group information corresponding to (step S202).
The representative value determining unit 122 executes the processing from S203.

  Further, the update unit 1004 updates the reference value, statistical value, and identification information of the group information including the target pixel.

  On the other hand, when the pixel intensity included in the target pixel data in step S201 is not included in the reference values of the first group information to the eighth group information (step S201: NO), the representative value determining unit 122 It is then determined whether there is group information for which no reference value has been set yet (step S204).

  Here, when there is group information for which a reference value has not yet been set (step S204: YES), the representative value determining unit 122 associates the target pixel with the group information (step S205). Note that the representative value determination unit 122 associates the pixels with the pixels in order from, for example, group information having a lower number.

  Also here, the reference value, statistical value, and identification information of the group information associated with the target pixel are updated. The representative value determining unit 122 executes the processing from step S203.

  When there is no group information for which no reference value is set yet (step S204: NO), the representative value determining unit 122 calculates a first distance in the color space between reference values for all group information. The distance calculation unit 1008 calculates a second distance in the color space between the intensity of the target pixel and the reference value of each group information.

When the first distance is the shortest among the first distance and the second distance, the representative value determination unit 122 integrates two group information related to the corresponding reference values to create a new group. Information is generated (step S206). Then, the representative value determination unit 122 generates new group information that is not yet associated with a pixel, and associates the target pixel with the new group information.
On the other hand, when the second distance is the shortest among the first distance and the second distance, the representative value determining unit 122 associates the group information of the corresponding reference value with the target pixel. The representative value determining unit 122 executes the processing from step S203.

  The representative value determination unit 122 updates the reference value, the statistical value, and the identification information of the group information based on the pixel data of the pixels associated with the group information.

  In step S203, the representative value determining unit 122 determines whether or not the association between each of the 8 pixels included in one block and the group information has been completed (step S203). When the association between each of the 8 pixels and the group information is completed (step S203: YES), the representative value determining unit 122 ends the association process. On the other hand, when the association between each of the 8 pixels and the group information has not been completed (step S203: NO), the representative value determining unit 122 repeats the processing from step S201.

  As described above, according to the image forming apparatus 1 of the present embodiment, the image processing unit 12 determines the number of groups smaller than the number of the plurality of pixels from the pixel values of the plurality of pixels included in the predetermined area of the image (for example, LUT including pixel values after image processing with respect to pixel values before image processing (for example, color conversion processing), by determining a representative value of pixel values of 8 groups), associating the plurality of pixels with any of the representative values , The pixel value after image processing corresponding to the representative value is obtained, and the pixel value of the plurality of pixels is used as the pixel value after image processing corresponding to the representative value associated with each pixel. The number of accesses to the LUT storage unit 123, which is a memory for referring to the image, can be set to the number of times corresponding to the number of representative value groups (for example, 8 times), and access corresponding to all pixels included in the predetermined area can be performed. L compared to the number of times Since it is possible to reduce the number of accesses to T storage unit 123 can perform image processing at a higher speed. In addition, it is possible to eliminate the need for processing units and memory according to the number of parallel processing in line-by-line parallel processing, which was a conventional method for speeding up image processing, and speeding up image processing and reducing memory capacity. And both.

  Moreover, since the representative value is an average value of the pixel values associated with the group information, the pixel value after the image processing can be made closer to the pixel value before the image processing.

  Further, the image processing unit 12 generates range information indicating a range of pixel values corresponding to each representative value as a reference value of the group information, and selects pixels having pixel values that are within the range of pixel values corresponding to the representative value. Since it is associated with the representative value, the association in consideration of the pixel value of each pixel can be performed in the association of each pixel with the representative value.

  The embodiment of the present invention should be considered that the embodiment disclosed this time is illustrative and not restrictive in all respects. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  For example, in the above embodiment, whether the intensity of the target pixel is within the range of the intensity (or luminance) of the pixel indicated by the maximum value and the minimum value of the intensity (or luminance) of the pixel included in the reference value. Whether or not the pixel data is included in the reference value is determined based on whether or not the pixel value is included in the reference value, but this is an example and the present invention is not limited to this. For example, as the reference values of the first group information to the eighth group information, the intensity values of the pixels associated so far are individually set, and in the determination of whether or not they are included in the reference values, the pixel data You may make it judge whether the intensity | strength of the pixel contained corresponds with the reference value of 1st group information-8th group information. In addition, various processes may be performed by replacing the pixel intensity in the above-described embodiment with the pixel luminance.

  In the group information in the above embodiment, the reference value is the maximum value and the minimum value of the pixel intensity, and the statistical value is the cumulative pixel intensity. However, the group information is an example and is not limited thereto. For example, the reference value may be an average value of pixel intensities, and the statistical value may be a maximum value and a minimum value of pixel intensities. Furthermore, the reference value may be the maximum value and the minimum value of the pixel intensity, and the statistical value may be an average value of the pixel intensity.

  Further, in order to save the use area of the register 1010, it is desirable that the amount of data to be stored is smaller. Therefore, for example, in step S102, the representative value determination unit 122 sets the group information number (index) associated with each pixel to “data indicating which group information is associated with” for each pixel (192 bits). = 64 pixels × 3 bits (group information identification number)). Further, the group information number (index) associated with each pixel is set to “flag indicating which pixel is included” for each group information (512 bits = 64 bits (ON / OFF for 64 pixels) × 8 groups). However, the former has a smaller amount of data.

  In addition, when preparing the group information in step S101, an average value is calculated from the accumulated RGB intensity and the number of pixels stored in the register 1010, and the same value (average value) is substituted for the maximum value and the minimum value. You may do it. Even with this configuration, the association between each pixel and any of the group information is performed correctly, and there is almost no change in image quality. Since the total is also stored, the average value that functions as the representative value is correctly calculated.

  Here, the register 1010 stores the average value of the intensity for each group information instead of the cumulative intensity for each group information as the statistical value of the temporary information, and the representative value determination unit 122 outputs the average value as the representative value. May be. Conversely, the register 1010 may store “maximum and minimum values of RGB intensity” as the statistical value of the temporary information, and the representative value determination unit 122 may calculate the cumulative value or the average value.

The method for determining the representative value in the above embodiment is merely an example, and the present invention is not limited to this. The representative value may be determined by another method.
For example, in the above embodiment, the average value is calculated as the representative value by dividing the cumulative value of the intensity of the pixels associated with the group information by the number of pixels, but instead of calculating the average value, the predetermined area The pixel value of a specific pixel in the image may be used as a representative value as it is. The average value may be a weighted average value or a square average value. Moreover, it is good also as an intermediate value instead of an average value. In addition, when there is a pixel that is regarded as a singular point based on intensity dispersion or deviation of each pixel associated with the group information, the average value or the intermediate value is calculated by excluding the singular point. Also good.
In addition, a plurality of dither groups for determining whether or not a pixel is included within a predetermined pixel intensity range may be provided, and the representative value may be determined according to the distribution of the number of pixels distributed by each dither group. .

  Further, the color conversion process determined by the LUT is not limited to the color conversion process from RGB to CMYK. Reverse color conversion processing may be performed, color conversion processing in the same color space may be performed, and color spaces other than RGB and CMYK may be employed.

In the above embodiment, the group information in which the intensity of the pixel included in the target pixel data is not included in the reference values of the first group information to the eighth group information, and the reference value is not yet set. Is not present, the first distance and the second distance are calculated and compared according to the result of comparison, but other methods may be used.
For example, in this case, the maximum value of the pixel values included in the pixel value range that is the reference value of the group information corresponding to one representative value, and the reference value of the group information corresponding to the other representative value. The group information of two representative values having the smallest difference from the minimum value of the pixel values included in the pixel value range is integrated, and new group information is generated for the group information in which one margin is generated by the integration. The target pixel may be associated with the new group information. In this case, for example, the integration process is performed by the integration unit 1009, and the association is performed by the classification unit 1003, for example.
In this case, the maximum or minimum pixel value included in the pixel value range that is the reference value of the group information is the group information corresponding to the pixel value range closest to the pixel value of the pixel and the target. Pixels may be associated with each other. In this case, the association is performed by, for example, the classification unit 1003 described above.
Also in these cases, as in the above-described embodiment, when performing image processing with representative values having a smaller number of groups than the number of pixels in the predetermined area, the distribution of pixels associated with each representative value is performed before image processing. The pixel value of the pixel can be considered more, and image processing can be performed in which the pixel value of each pixel before image processing is more considered.

  In the above embodiment, image processing is performed using eight representative values corresponding to eight groups of the first group information P1 to the eighth group information P8. Is merely an example, and the present invention is not limited to this. The number of accesses to the LUT performed during image processing can be reduced if the number is smaller than the number of pixels included in a predetermined area of the image.

Further, image processing may be performed without performing interpolation calculation. In other words, the present invention does not prevent the image processing from being performed using the LUT including the data corresponding to all the pixel values that can be the pixel values before and after the image processing.
In addition, when performing image processing by interpolation calculation, any interpolation calculation method that can be employed at present or in the future can be used.

  The image forming apparatus 1 in the above embodiment is an ink jet recording apparatus, but may be an image forming apparatus that forms an image by another method. For example, any type of image forming apparatus capable of forming an image on a recording medium, such as an electrophotographic system, a thermal transfer system, an offset system, or the like can be employed in the image forming system.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Communication part (Image acquisition means)
12 Image processing unit (image processing apparatus, image processing means)
13 Image forming unit (image forming means)
14 operation display unit 15 central control unit 121 pixel value acquisition unit 122 representative value determination unit (association unit, determination unit)
123 LUT storage unit (storage means)
124 representative value converter (acquisition means)
125 pixel value assignment unit (processing means)
1001 Line switching unit 1002 Pixel switching unit 1003 Classification unit (associating means)
1004 Update unit (generation means)
1005 Determination unit (determination means)
1006 Judgment Unit 1007 Judgment Unit 1008 Distance Calculation Unit 1009 Integration Unit 1010 Register

Claims (11)

An image processing apparatus that performs predetermined image processing on each of a plurality of pixels constituting an image,
Associating means for associating a plurality of pixels included in a predetermined region of an image with any one of a number of groups smaller than the number of the plurality of pixels;
Determining means for determining a representative value of each group based on a pixel value of a pixel associated with each group;
Storage means for storing the pixel value after the predetermined image processing with respect to the pixel value before the predetermined image processing;
Obtaining means for obtaining the pixel value after the predetermined image processing corresponding to the representative value from the storage means;
Processing means for setting pixel values of pixels associated with each group to pixel values after the predetermined image processing corresponding to representative values of each group;
An image processing apparatus comprising:   The image processing apparatus according to claim 1, wherein the determining unit sets an average value of pixel values associated with each group by the association unit as a representative value of each group. A generating unit that generates range information indicating a range of pixel values corresponding to each group;
The image processing apparatus according to claim 1, wherein the association unit associates a plurality of pixels included in the predetermined area with each group based on a range of pixel values corresponding to each group. 4. The apparatus according to claim 1, wherein the association unit associates the plurality of pixels with each group based on pixel values of the plurality of pixels included in the predetermined region. 5. Image processing device. 5. The image according to claim 4, wherein the association unit associates the plurality of pixels with each group sequentially for each pixel based on the pixel values of the plurality of pixels included in the predetermined region. Processing equipment. The association unit sequentially associates the plurality of pixels with each group for each pixel based on a range of pixel values corresponding to each group and each pixel value of the plurality of pixels.
The image processing apparatus according to claim 3, wherein the generation unit updates range information indicating a range of pixel values of the associated group after completion of association of one pixel by the association unit. . The predetermined image processing is color conversion processing from RGB to CMYK,
7. The image according to claim 1, wherein the storage unit stores a pixel value in the CMYK color space after the color conversion process for a pixel value in the RGB color space before the color conversion process. Processing equipment. Until the predetermined image processing for all the pixels constituting the image is completed, the processing by the association unit, the processing by the determination unit, the processing by the acquisition unit, and the processing by the processing unit are repeated. The image processing apparatus according to claim 1, wherein: The plurality of pixels included in the predetermined region form a plurality of pixel lines, and the number of pixels constituting each pixel line is equal to the number of the groups. The image processing apparatus described. The number of the groups is set to one predetermined value when the association unit starts associating a plurality of pixels included in the predetermined area. The image processing apparatus according to item 1. Image acquisition means for acquiring images;
Image processing means for performing predetermined image processing on each of a plurality of pixels constituting the image acquired by the image acquisition means;
An image forming apparatus comprising: an image forming unit that forms an image based on an image that has been subjected to predetermined image processing by the image processing unit;
The image processing means includes
An image forming apparatus comprising the image processing apparatus according to claim 1 .

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