Image processing device, image processing method

Abstract

To provide a technique for, in head shading for an image, reducing processing performance degradation and increase in scale of performance configuration.SOLUTION: A first image obtained by performing first head shooting for a band image which is an image of a band unit, a second image obtained by performing second head shading for the first image are alpha-blended. A coefficient in alfa-blending is switched for each line in the band image.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to image processing technology.

Background Art

[0002] In a recording head used in an inkjet recording apparatus, due to manufacturing variations and other reasons, variations may occur in ejection characteristics (such as ejection amount and ejection direction) among a plurality of nozzles. With such variations, density unevenness occurs in the recorded image. Therefore, in an inkjet printer, it is known to use head shading (HS) technology as calibration of ejection characteristics as described in Patent Document 1. Further, in an inkjet printer that performs printing in full color, not only HS, which is a single-color correction, but also correction called color shading, which calibrates multiple colors as described in Patent Document 2, is performed to suppress variations in ejection characteristics and obtain a printed image with less color unevenness.

[0003] Also, in a serial printer, HS may be required in a vertical connection head (a configuration in which recording heads are connected vertically) or the like due to the elongation of the nozzle row due to high-speed operation. In the case of changing the HS correction amount in one nozzle row and performing multi-pass printing, in a system that performs HS on multi-valued data before quantization, while having the feature of enabling fine gradation correction, the pixels of a certain line of image data and the positions of the nozzles that eject those pixels may not be in a one-to-one correspondence. Therefore, as described in Patent Document 3, it is also necessary to correct based on the HS of the nozzle row and the contribution rate for each nozzle row.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, such correction generally uses table conversion processing by a LUT (Look Up Table) according to the ejection characteristics of the nozzles of the recording head. In an inkjet device equipped with a vertical connection head, in order to strictly correspond with HS, it is necessary to correspond with different HS tables for each nozzle used in each pass in multi-pass. Therefore, measures such as overlapping and correcting multiple HS tables for the same pixel and adjusting the effectiveness of the correction in line units are required, but the processing efficiency is poor and deteriorates. Also, due to arranging multiple tables, the circuit scale and processing load are greatly affected, which is difficult.

[0006] Further, in an inkjet device equipped with a line head that uses a large number of nozzle arrays corresponding to the page width for image formation, when performing page processing, it is necessary to have an HS table according to the position of the nozzles and switch and use the HS table according to the position of the image to be formed. However, when processing an image of one page, it is necessary to replace the HS table many times, and the memory bandwidth and replacement processing time during transfer affect the performance and circuit scale. Also, although the performance is improved by reducing the number of times of switching the HS table, since it is a trade-off relationship with the correction accuracy of HS, it has been required to improve the performance by reducing the frequency of table replacement for HS correction. The present invention provides a technique for reducing the decrease in processing performance and the increase in the scale of the configuration to be implemented in head shading for an image.

Means for Solving the Problems

[0007] One aspect of the present invention includes alpha blending means for alpha blending a first image obtained by performing first head shading on a band image, which is an image in units of bands, and a second image obtained by performing second head shading on the first image, and the alpha blending means is characterized in that the coefficient in the alpha blending is switched for each line in the band image.

Effect of the Invention

[0008] According to the present invention, in head shading for an image, it is possible to provide a technique for reducing a decrease in processing performance and an increase in the scale of the configuration to be implemented.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant descriptions are omitted.

[0011] [First Embodiment] In this embodiment, a case where an inkjet printer is used as a recording device will be described. A hardware configuration example of the inkjet printer 200 according to this embodiment will be described with reference to the block diagram of FIG. 2. Note that FIG. 2 shows the configurations related to the following description and does not show all the configurations of the inkjet printer.

[0012] The input unit 203 performs data communication with an external device. For example, the input unit 203 receives a multi-valued image (image to be printed) to be printed transmitted from the external device and stores the image to be printed in the main memory 202.

[0013] The control unit 204 includes one or more processors and one or more memories, and executes various processes using the computer programs and data stored in the memories and the main memory 202. Thereby, the control unit 204 controls the operation of the entire inkjet printer 200 and executes or controls various processes described as the processes performed by the inkjet printer 200.

[0014] The main memory 202 has an area for storing a computer program and data loaded from the memory of the control unit 204, and an area for storing data received by the input unit 203 from an external device. Further, the main memory 202 has a work area used when the control unit 204, the processing unit 201, and the generation unit 207 execute various processes. In this way, the main memory 202 can appropriately provide various areas.

[0015] The processing unit 201 performs head shading (HS) on a print target image input as an input image. In the present embodiment, the "print target image" will be described for the case of a CMYK image in which each pixel has a pixel value of C (cyan), a pixel value of M (magenta), a pixel value of Y (yellow), and a pixel value of K (black).

[0016] A configuration example of the processing unit 201 will be described with reference to the block diagram of FIG. 1. As shown in FIG. 1, the processing unit 201 has a processing unit 101 and a processing unit 100. The control unit 204 divides the print target image into a plurality of bands (band images), stores the band images in the main memory 202, and controls the DMAC to transfer the band images from the main memory 202 to the processing unit 201. Note that the method of transferring the band images stored in the main memory 202 to the processing unit 201 is not limited to a specific method. An example of dividing the print target image into a plurality of band images is shown in FIG. 4. In FIG. 4, the print target image 400 is divided into units of band images 400, which are horizontally long rectangular images (band units). However, the method of dividing the print target image is not limited to a specific method, and for example, it may be divided in a grid pattern.

[0017] In the HS correction unit 104a, an image (C image) composed of the pixel values of C for each pixel of the band image, an image (M image) composed of the pixel values of M for each pixel of the band image, an image (Y image) composed of the pixel values of Y for each pixel of the band image, and an image (K image) composed of the pixel values of K for each pixel of the band image are input via the signal line group 103. The HS correction unit 104a performs HS (first HS) on each of the C image, M image, Y image, and K image to generate a C' image, M' image, Y' image, and K' image. For example, the HS correction unit 104a uses an HS table Cmin, which is a one-dimensional LUT for converting the pixel values in the C image into the pixel values in the C' image, to generate the C' image corresponding to the C image. Similarly, the HS correction unit 104a uses an HS table Mmin, which is a one-dimensional LUT for converting the pixel values in the M image into the pixel values in the M' image, to generate the M' image corresponding to the M image. Similarly, the HS correction unit 104a uses an HS table Ymin, which is a one-dimensional LUT for converting the pixel values in the Y image into the pixel values in the Y' image, to generate the Y' image corresponding to the Y image. Similarly, the HS correction unit 104a uses an HS table Kmin, which is a one-dimensional LUT for converting the pixel values in the K image into the pixel values in the K' image, to generate the K' image corresponding to the K image. The first HS is an HS correction when the density of the recorded image ejected due to the variation in the nozzles of the recording head of the inkjet printer 200 becomes low. Then, the HS correction unit 104a outputs the C' image, M' image, Y' image, and K' image via the signal line group 105.

[0018] The HS correction unit 104b receives the C’ image, M’ image, Y’ image, and K’ image via the signal line group 105. The HS correction unit 104b performs a second HS, which is different from the first HS, on each of the C’ image, M’ image, Y’ image, and K’ image to generate a C” image, M” image, Y” image, and K” image. For example, the HS correction unit 104b uses an HS table Cmax, which is a one-dimensional LUT for converting the pixel values in the C’ image into the pixel values in the C” image, to generate the C” image corresponding to the C’ image. Similarly, the HS correction unit 104b uses an HS table Mmax, which is a one-dimensional LUT for converting the pixel values in the M’ image into the pixel values in the M” image, to generate the M” image corresponding to the M’ image. Similarly, the HS correction unit 104b uses an HS table Ymax, which is a one-dimensional LUT for converting the pixel values in the Y’ image into the pixel values in the Y” image, to generate the Y” image corresponding to the Y’ image. Similarly, the HS correction unit 104b uses an HS table Kmax, which is a one-dimensional LUT for converting the pixel values in the K’ image into the pixel values in the K” image, to generate the K” image corresponding to the K’ image. The second HS is an HS correction when the density of the recorded image increases due to variations in the nozzles of the recording head of the inkjet printer 200.

[0019] In the α coefficient table 108, for each line in the band image, the coefficient (α value) used in the alpha blending for the line is registered for each component (color component). A configuration example of the α coefficient table 108 is shown in FIG. 9. In the α coefficient table 108 shown in FIG. 9, the coefficients (α values) used in the alpha blending for a band image with 12 lines are registered for each line and each component. For example, in the α coefficient table 108, “26” is registered as the α value of the component C0 (C) in the line with line number = 2, “31” is registered as the α value of the component C1 (M), “10” is registered as the α value of the component C2 (Y), and “17” is registered as the α value of the component C3 (K).

[0020] The α - blending unit 106a generates a processed C image by performing alpha - blending for each line of the C' image, using the line, the corresponding line in the C'' image corresponding to the line, and the α value of the component C0(C) corresponding to the line number of the line in the α - coefficient table 108.

[0021] Here, let the pixel value of the target pixel in the target line of the C' image be P1, the pixel value of the corresponding target pixel corresponding to the target pixel in the C'' image be P2, and the α value of the component C0(C) corresponding to the line number of the target line in the α - coefficient table 108 be α1. At this time, the α - blending unit 106a obtains the pixel value P3 of the pixel corresponding to the target pixel in the processed C image as P3 = α1×P1+(1 - α1)×P2.

[0022] Similarly, the α - blending unit 106b generates a processed M image by performing alpha - blending for each line of the M' image, using the line, the corresponding line in the M'' image corresponding to the line, and the α value of the component C1(M) corresponding to the line number of the line in the α - coefficient table 108.

[0023] Similarly, the α - blending unit 106c generates a processed Y image by performing alpha - blending for each line of the Y' image, using the line, the corresponding line in the Y'' image corresponding to the line, and the α value of the component C2(Y) corresponding to the line number of the line in the α - coefficient table 108.

[0024] Similarly, the α - blending unit 106d generates a processed K image by performing alpha - blending for each line of the K' image, using the line, the corresponding line in the K'' image corresponding to the line, and the α value of the component C3(K) corresponding to the line number of the line in the α - coefficient table 108.

[0025] In this way, the processing unit 201 switches and uses the coefficients for alpha blending from the alpha coefficient table 108 for each line and component in the band image. More specifically, in the present embodiment, the processing unit 201 takes the line number of the line to be processed in the band image and the component to be processed in the line as arguments, and acquires the corresponding alpha value from the alpha coefficient table 108. However, the method of switching the alpha value for each line and component in the band image is not limited to using the alpha coefficient table 108. For example, the processing unit 201 may hold a function representing the relationship between the line position and the alpha value in the band image for each component, and acquire the alpha value corresponding to the line position to be processed from the function corresponding to the component to be processed.

[0026] Then, the processing unit 100 outputs the processed images (processed C image, processed M image, processed Y image, processed K image) via the signal line group 107. The control unit 204 controls the DMAC to transfer the processed image to the main memory 202.

[0027] Then, the processing unit 201 performs quantization processing such as dither processing or error diffusion processing on the processed images (processed C image, processed M image, processed Y image, processed K image) transferred to the main memory 202, and converts the processed images into binary data indicating "1" for recording (ink ejection) and "0" for non-recording (no ink ejection). Then, the processing unit 201 stores the binary data as recording data in the main memory 202.

[0028] The generation unit 207 reads out the data of each pixel in the recording data stored in the main memory 202 in a predetermined order, associates it with each nozzle of the recording head of the recording processing unit 205, and supplies it to the recording processing unit 205.

[0029] As shown in FIG. 5, the recording processing unit 205 includes a recording head 503 in which a plurality of nozzle arrays 507 each having nozzles for ejecting ink droplets are arranged in a number corresponding to the ink colors, a transport mechanism 504 for performing a transport operation of the print medium P, and the like. In the present embodiment, the nozzle array 507 has a length corresponding to an area in the X direction (a direction orthogonal to the transport direction Y of the print medium P) printable on the print medium P.

[0030] The receiving unit 501 receives the recording data supplied from the generating unit 207. The control unit 502 drives and controls the recording head 503 and the transport mechanism 504 according to the recording data, thereby printing an image or characters on the print medium P and transporting the print medium P in the transport direction Y.

[0031] Next, the correspondence relationship between the recording head 503 and the image to be printed will be described with reference to FIG. 6. The nozzle array 507 is an aggregate of ejection nozzles 600 in units of one dot. In FIG. 6, only one row is shown for simplification. Also, in the case of color printing, there may be a configuration in which there are multiple rows of nozzles corresponding to each ink color such as C, M, Y, and K, and which nozzle of the recording head 503 each pixel in the image 400 to be printed is recorded on is associated in advance. Since the image 400 to be printed is processed band by band, one-page image is divided into a plurality of bands such as band 601, band 602, band 603, and band 604. For HS for band 601, the LUT of the region corresponding to band 601 in the nozzle array 507 is used. For HS for band 602, the LUT of the region corresponding to band 602 in the nozzle array 507 is used. By performing HS according to the band in this way, a recording result with less color unevenness due to ejection variation can be obtained.

[0032] The input unit 203, the control unit 204, the main memory 202, the processing unit 201, and the generating unit 207 are all connected to the system bus 206.

[0033] Here, the HS will be described. In order to accurately adjust the variation for each nozzle of the ejection nozzle 600, it is necessary to perform HS corresponding to the nozzle for each pixel. In the present embodiment, since the band image has 12 lines, as shown in FIG. 9, for one component, 12 α values (HS adjustment parameters) equal to the number of lines are required.

[0034] An example of a recorded image due to the variation of the ejection nozzle 600 is shown in FIG. 7. Each rectangular area is a recording area of one pixel on the print medium, and the circles within the rectangular area are dots when ink droplets are recorded on the print medium. In FIGS. 7(a) and 7(b), the state where the sizes of the dots are different due to the variation of the ejection nozzle 600 is illustrated. As shown in FIG. 7(a), when the dots become small, many portions (white) where no dots exist on the print medium are exposed, and the density of the recorded image on the print medium is decreased. On the other hand, as shown in FIG. 7(b), when the dots become large, the exposure of the portions (white) where no dots exist on the print medium is small, and the density of the recorded image on the print medium is increased.

[0035] Assuming that both FIGS. 7(a) and 7(b) represent the results of recording an image with a density of 50% without HS, the results of recording images with increased / decreased density via HS are shown in FIGS. 8(a) and 8(b), respectively.

[0036] As shown in Fig. 7(a), when small dots are recorded, HS is performed to correct the image so that an image with a density of about 80% can be obtained. On the other hand, as shown in Fig. 7(b), when large dots are recorded, HS is performed to correct the image so that an image with a density of about 33% can be obtained. Then, when the pixel values of the HS-processed image are quantized to form a dot pattern, a pattern with different thinning amounts depending on the size of the dots is formed as shown in Fig. 8. Fig. 8(a) shows a dot pattern formed based on an image obtained by performing HS to correct the image so that an image with a density of about 80% can be obtained. Fig. 8(b) shows a dot pattern formed based on an image obtained by performing HS to correct the image so that an image with a density of about 33% can be obtained. Although Fig. 8 shows extreme examples for the sake of explanation, the quantization pattern and the correction amount regarding the density are not limited to this. The HS of this embodiment performs correction based on a criterion such as the size of these dots.

[0037] In this embodiment, the minimum size (or a size smaller than the minimum size) of the dots of the ink droplets ejected from the nozzles corresponding to the band images is measured / acquired in advance (for example, at the time of factory shipment of the inkjet printer 200) as size S1. Then, a one-dimensional LUT (Cmin, Mmin, Ymin, Kmin) for correcting the "image of normal density" to an "image with a density higher than the density of the image recorded without HS for the image of normal density" (HS correction) is generated based on size S1 and registered in the inkjet printer 200. Therefore, the first HS, which is the HS performed using such a LUT, is a process of correcting the "image of normal density" to an "image with a density higher than the density of the image recorded without HS for the image of normal density".

[0038] Also, in the present embodiment, the maximum size (or a size larger than the maximum size) of the dots of the ink droplets ejected from the nozzles corresponding to the band images is measured / obtained in advance (for example, at the time of factory shipment of the inkjet printer 200) as size S2. Then, a one-dimensional LUT (Cmax, Mmax, Ymax, Kmax) for correcting (HS correction) the "image with normal density" to an "image with a density lower than the density of the image recorded without HS for the image with normal density" is generated based on size S2 and registered in the inkjet printer 200. Therefore, the second HS, which is the HS performed using such a LUT, is a process of correcting the "image with normal density" to an "image with a density lower than the density of the image recorded without HS for the image with normal density".

[0039] Note that when the processing unit 201 generates recording data for one band image, for the next process, it updates the parameters that need to be changed for each band. For example, since HS needs to be performed according to the HS corresponding to the nozzles for the next band, an update is necessary. However, Cmin, Mmin, Ymin, Kmin, Cmax, Mmax, Ymax, and Kmax can be continuously used as long as the amount of HS correction existing within the band is between the first HS and the second HS. Therefore, it becomes possible to perform the HS for the next band by updating the α coefficient table 108, and the parameter transfer amount can be reduced. As a result, it becomes possible to reduce the processing time and the access amount to the main memory. Note that the α coefficient table 108 may or may not be updated depending on the case.

[0040] The printing process of the image to be printed by the inkjet printer 200 will be described according to the flowchart of FIG. 3. In step S301, the control unit 204 divides the image to be printed into a plurality of bands (band images), controls the DMAC, and transfers the band images to the processing unit 201. The processes in steps S302 to S306 are performed for each of the plurality of band images.

[0041] In step S302, the HS correction unit 104a performs first HS on each of the C image, M image, Y image, and K image to generate a C' image, M' image, Y' image, and K' image.

[0042] In step S303, the HS correction unit 104b performs second HS on each of the C' image, M' image, Y' image, and K' image to generate a C" image, M" image, Y" image, and K" image.

[0043] In step S304, the α blending unit 106a refers to the α coefficient table 108 and performs α blending on the C' image and the C" image to generate a processed C image. The α blending unit 106b refers to the α coefficient table 108 and performs α blending on the M' image and the M" image to generate a processed M image. The α blending unit 106c refers to the α coefficient table 108 and performs α blending on the Y' image and the Y" image to generate a processed Y image. The α blending unit 106d refers to the α coefficient table 108 and performs α blending on the K' image and the K" image to generate a processed K image.

[0044] In step S305, the processing unit 201 performs quantization processing such as dither processing or error diffusion processing on the processed images (processed C image, processed M image, processed Y image, processed K image) to convert the processed images into binary data.

[0045] In step S306, the generation unit 207 reads out the data of each pixel in the recording data in a predetermined order, associates it with each nozzle of the recording head included in the recording processing unit 205, and supplies it to the recording processing unit 205. The recording processing unit 205 drives and controls the recording head 503 and the conveyance mechanism 504 according to the recording data to print an image and characters on the printing medium P and convey the printing medium P in the conveyance direction Y.

[0046] [Second Embodiment] In this embodiment, the differences from the first embodiment will be described, and unless otherwise specified below, it is assumed to be the same as the first embodiment. In the first embodiment, a case where it is applied to an HS corresponding to an inkjet printer having a line head was described. In this embodiment, a case where it is applied to an HS corresponding to a printer that forms a recorded image on a print medium by scanning a recording head a plurality of times, such as a serial printer, will be described.

[0047] A configuration example of the processing unit 205 according to this embodiment will be described with reference to FIG. 10. In FIG. 10, the same reference numerals are assigned to the functional units similar to those shown in FIG. 5, and the description of the functional units will be omitted or briefly described.

[0048] The recording head 1001 is provided with a number of nozzle arrays 1002 in which a plurality of nozzles for discharging ink as droplets are arranged, corresponding to the number of ink colors. The control unit 1003 drives and controls the recording head 1001 and the conveyance mechanism 504 according to the recording data received by the receiving unit 501, thereby printing an image or characters on the print medium P and conveying the print medium P in the conveyance direction Y.

[0049] The processing unit 205 alternately repeats a recording scan in which it moves in the X direction orthogonal to the arrangement direction (Y direction) of the nozzles while discharging ink from the nozzle array 1002, and a conveyance operation in which the print medium P is conveyed in the Y direction by a distance corresponding to the recording width by the recording scan, thereby recording an image or characters on the print medium P.

[0050] Next, the correspondence between the recording head 1001 and the image to be printed will be described with reference to FIG. 11. The nozzle array 1002 of the recording head 1001 is an aggregate of ejection nozzles 1100 in units of one dot. In FIG. 11, only one row is shown for simplicity, but there may be multiple rows. Also, in the case of color printing, there may be a configuration in which there are multiple rows of nozzles with different ink colors such as C, M, Y, and K. Each pixel in the image 400 to be printed is associated in advance with which nozzle of the recording head 1001 it will be recorded by. Since the image 400 to be printed is processed band by band, one page of the image is divided into a plurality of bands such as band 1107, band 1108, band 1109, and band 1110.

[0051] The nozzle array positions 1103, 1104, 1105, and 1106 represent the positions of the nozzle array 1002 when the recording head 1001 scans the printing medium P in the X direction. In this embodiment, as an example, four-pass printing will be described, that is, the case where when recording band 1107 on the printing medium P, the scanning in the X direction is performed four times, and the recording is performed while shifting by 1 / 4 of the band height of band 1107 in the Y direction. In FIG. 11, a case where the length of the nozzle array 1002 is the same as the band height of bands 1107 to 1110 is shown, but they do not have to be the same. Different from the first embodiment, in this embodiment, when processing band 1107, there are a plurality of regions of the nozzle array 1002 corresponding to band 1107. Therefore, in this embodiment, it is necessary to switch the LUT according to the four recording scan positions of the nozzle array positions 1103 to 1106 and perform HS. The relationship between the position of the nozzle array 1002 when printing on the printing medium P by four-pass printing and the printing medium P will be described with reference to FIG. 12 using band 1107 as an example.

[0052] The relationship between the nozzle row 1002 and the HS will be described with reference to FIG. 12(a). In FIG. 12(a), the nozzle row 1002 is divided into four regions. The nozzle row belonging to the uppermost region performs ink ejection based on an image obtained by performing HS using HS1 as the LUT. The nozzle row belonging to the second region from the top performs ink ejection based on an image obtained by performing HS using HS2 as the LUT. The nozzle row belonging to the third region from the top performs ink ejection based on an image obtained by performing HS using HS3 as the LUT. The nozzle row belonging to the lowermost region performs ink ejection based on an image obtained by performing HS using HS4 as the LUT. Thereby, a recording image with less unevenness can be obtained on the printing medium P.

[0053] In FIG. 12(b), the nozzle row positions 1201, 1202, 1203, and 1204 represent the relative positional relationship between the nozzle row 1002 and the band 1107 when the recording head 1001 scans the printing medium P in the X direction.

[0054] The nozzle row position 1201 indicates the position of the nozzle row 1002 in the first search, and the nozzle row position 1202 indicates the position of the nozzle row 1002 in the second search. Also, the nozzle row position 1203 indicates the position of the nozzle row 1002 in the third search, and the nozzle row position 1204 indicates the position of the nozzle row 1002 in the fourth search. All the nozzles of the nozzle row 1002 scan the recording area 1200 in the band 1107 and perform image formation on the recording area 1200 in four scans. Also, when the total discharge amount to the recording area 1200 is set to 100%, the discharge amount may be adjusted according to the corresponding print pass, such as 40% at the nozzle row position 1201, 10% at the nozzle row position 1202, 10% at the nozzle row position 1203, and 40% at the nozzle row position 1204. When applying HS in a multi-valued state, since the recording area 1200 becomes one image, it is difficult to reflect different HS values. In contrast, in this embodiment, the recording area 1200 is configured to be able to reflect the results of applying HS1, the results of applying HS2, the results of applying HS3, and the results of applying HS4, each with an intensity of 40%, 10%, 10%, and 40%.

[0055] A configuration example of the processing unit 201 according to this embodiment will be described with reference to the block diagram of FIG. 13. FIG. 13 shows a case where printing is performed by four-pass printing on the print medium P.

[0056] The control unit 204 divides the X (X = C, M, Y, K) image into a pass image R1 that is an image of the area to be printed in the first pass in the X image, a pass image R2 that is an image of the area to be printed in the second pass in the X image, a pass image R3 that is an image of the area to be printed in the third pass in the X image, and a pass image R4 that is an image of the area to be printed in the fourth pass in the X image. Then, the control unit 204 inputs the pass images R1 to R4 to the processing unit 201.

[0057] The HS correction unit 104c performs HS on each of the pass images R1 to R4 to generate pass images R'1 to R'4. For example, the HS correction unit 104c uses HS1, which is a one-dimensional LUT for converting the pixel values in the pass image R1 into the pixel values in the pass image R'1, to generate the pass image R'1 corresponding to the pass image R1. Similarly, the HS correction unit 104c uses HS2, which is a one-dimensional LUT for converting the pixel values in the pass image R2 into the pixel values in the pass image R'2, to generate the pass image R'2 corresponding to the pass image R2. Similarly, the HS correction unit 104c uses HS3, which is a one-dimensional LUT for converting the pixel values in the pass image R3 into the pixel values in the pass image R'3, to generate the pass image R'3 corresponding to the pass image R3. Similarly, the HS correction unit 104c uses HS4, which is a one-dimensional LUT for converting the pixel values in the pass image R4 into the pixel values in the pass image R'4, to generate the pass image R'4 corresponding to the pass image R4.

[0058] In the α coefficient table 1301, for each pass image in the band image, the coefficient (α value) used in the alpha blending for the pass image is registered for each component (color component).

[0059] The α blending unit 106a performs alpha blending using the pass image R1, the pass image R'1, and the α value (for example, 0.4) corresponding to the pass image R1 and the component X in the α coefficient table 1301 to generate the processed image R”1.

[0060] Here, let the pixel value of the target pixel in the pass image R1 be P1, the pixel value of the corresponding target pixel corresponding to the target pixel in the pass image R'1 be P2, and the α value corresponding to the pass image R1 and the component X in the α coefficient table 1301 be α1. At this time, the α blending unit 106a obtains the pixel value P3 of the pixel corresponding to the target pixel in the processed image R”1 as P3 = α1 × P1 + (1 - α1) × P2.

[0061] Similarly, the α - blending unit 106b performs alpha - blending using the pass image R2, the pass image R'2, and the α value (e.g., 0.1) corresponding to the pass image R2 and the component X in the α - coefficient table 1301, thereby generating the processed image R”2.

[0062] Similarly, the α - blending unit 106b performs alpha - blending using the pass image R3, the pass image R'3, and the α value (e.g., 0.1) corresponding to the pass image R3 and the component X in the α - coefficient table 1301, thereby generating the processed image R”3.

[0063] Similarly, the α - blending unit 106d performs alpha - blending using the pass image R4, the pass image R'4, and the α value (e.g., 0.4) corresponding to the pass image R4 and the component X in the α - coefficient table 1301, thereby generating the processed image R”4.

[0064] The merge circuit 1302 merges the processed images R1 to R”4 (arranged according to the positional relationship of the corresponding pass images) to generate a single processed X - image and outputs the processed X - image.

[0065] The processing unit 1300 performs all of the above operations for all components (C, M, Y, K), thereby generating and outputting the processed C - image corresponding to the C - image, the processed M - image corresponding to the M - image, the processed Y - image corresponding to the Y - image, and the processed K - image corresponding to the K - image. The subsequent operations of the ink - jet printer 200 are the same as those in the first embodiment.

[0066] The printing process of the print - target image by the ink - jet printer 200 will be described according to the flowchart of FIG. 14. In the flowchart of FIG. 14, the same step numbers are assigned to the processing steps similar to those shown in FIG. 3, and the description of the processing steps is omitted. The processing in steps S1402 to S1404 is performed for each component for each of the plurality of band images.

[0067] In step S1401, the control unit 204 divides the print target image into a plurality of bands (band images). Then, the control unit 204 divides the X (X = C, M, Y, K) image into pass images R1 to R4. In step S1402, the HS correction unit 104c performs HS on each of the pass images R1 to R4 to generate pass images R'1 to R'4.

[0068] In step S1403, the α - blending unit 106a refers to the α - coefficient table 1301 and performs α - blending of the pass image R1 and the pass image R'1 to generate a processed image R”1. The α - blending unit 106b refers to the α - coefficient table 1301 and performs α - blending of the pass image R2 and the pass image R'2 to generate a processed image R”2. The α - blending unit 106c refers to the α - coefficient table 1301 and performs α - blending of the pass image R3 and the pass image R'3 to generate a processed image R”3. The α - blending unit 106d refers to the α - coefficient table 1301 and performs α - blending of the pass image R4 and the pass image R'4 to generate a processed image R”4.

[0069] In step S1404, the merge circuit 1302 merges the processed images R1 to R”4 (arranges them according to the positional relationship of the corresponding pass images) to generate a single image as the processed X image, and outputs the processed X image.

[0070] Note that a configuration that switches between using the first embodiment and the second embodiment is also conceivable. For example, the processing unit 201 may be configured to include a switching unit that switches the input destination of the band image between the processing unit 101 and the processing unit 1300, and a switching unit that switches the output destination of the α - blending units 106a to 106d between the main memory 202 and the merge circuit 1302.

[0071] In addition, in this embodiment, the processing unit 1300 performs processing on all components, but the processing unit 1300 for processing the C image, the processing unit 1300 for processing the M image, the processing unit 1300 for processing the Y image, and the processing unit 1300 for processing the K image may be provided. In this case, by operating each processing unit 1300 in order in a pipelined manner, it becomes possible to perform a complex HS on all components.

[0072] Furthermore, in the description of the line head printer of the first embodiment, an inkjet type line head was described, but it is not limited to this, and an LED printer using a light emitting diode (LED) instead of a laser as a light source may be used. The LED head of the LED printer has a plurality of fine LEDs arranged in parallel in a straight line, and printing is performed by drawing an image on a photoreceptor using it as a light source. In the configuration of this LED head, there is variation in the light amount for each LED, and it is necessary to suppress the variation in the light amount of one line by shading in pixel units. Therefore, by applying the HS described in the first embodiment, the light amount of the LED can be adjusted instead of the ink ejection amount.

[0073] Also, the functional units excluding the α coefficient table 108 in the processing unit 201 and the functional units excluding the α coefficient table 1301 in the processing unit 1300 may be implemented in hardware or software.

[0074] The numerical values, processing timings, processing order, processing subjects, data (information) acquisition methods / destinations / sources / storage locations, etc. used in the above embodiments are given as examples for specific explanations, and are not intended to be limited to such examples.

[0075] In addition, some or all of the above-described embodiments may be appropriately combined and used. Also, some or all of the above-described embodiments may be selectively used.

[0076] (Other Embodiments) The present invention can also be realized by supplying a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. It can also be realized by a circuit (for example, ASIC) that implements one or more functions.

[0077] The invention described in this specification includes the following image processing apparatus and image processing method. (Item 1) Alpha blending means for alpha blending a first image obtained by performing first head shading on a band image that is an image in units of bands, and a second image obtained by performing second head shading on the first image. The alpha blending means switches the coefficient in the alpha blending for each line in the band image. An image processing apparatus characterized by the above. (Item 2) Furthermore, The image processing apparatus according to Item 1, further comprising dividing means for dividing an input image into a plurality of band images. (Item 3) Furthermore, The image processing apparatus according to Item 1 or 2, further comprising holding means for holding the coefficient in the alpha blending for each line in the band image. (Item 4) Alpha blending means for alpha blending a first image that is an image for each print pass in a band image that is an image in units of bands, and a second image obtained by performing head shading on the first image. The alpha blending means switches the coefficient in the alpha blending for each first image. An image processing apparatus characterized by the above. (Item 5) Furthermore, The image processing apparatus according to item 4, comprising dividing means for dividing an input image into a plurality of band images and further dividing the band images into path images for each printing pass. (Item 6) Furthermore, The image processing apparatus according to item 4 or 5, further comprising holding means for holding coefficients in the alpha blending for each of the first images. (Item 7) Furthermore, The image processing apparatus according to any one of items 1 to 6, further comprising printing means for performing printing based on an image obtained by alpha blending by the alpha blending means. (Item 8) The image processing apparatus according to item 7, wherein the printing means performs printing by a line head based on an image obtained by alpha blending by the alpha blending means. (Item 9) The image processing apparatus according to item 7, wherein the printing means performs printing by an LED head based on an image obtained by alpha blending by the alpha blending means. (Item 10) An image processing method performed by an image processing apparatus, wherein the alpha blending means of the image processing apparatus performs alpha blending between a first image obtained by performing first head shading on a band image which is an image in band units and a second image obtained by performing second head shading on the first image, and switches coefficients in the alpha blending for each line in the band image. An image processing method characterized by the above. (Item 11) An image processing method performed by an image processing apparatus, The alpha blending means of the image processing apparatus performs alpha blending on a first image that is an image for each printing pass in a band image that is an image in units of bands, and a second image obtained by performing head shading on the first image. Switch the coefficient in the alpha blending for each first image. An image processing method characterized by the above.

[0078] The invention is not limited to the above embodiments, and various changes and modifications are possible without departing from the spirit and scope of the invention. Therefore, claims are attached to disclose the scope of the invention.

Explanation of Signs

[0079] 100: Processing unit 101: Processing unit 103: Signal line group 104a: HS correction unit 104b: HS correction unit 105: Signal line group 106a: Alpha blending unit 106b: Alpha blending unit 106c: Alpha blending unit 106d: Alpha blending unit 107: Signal line group 108: Alpha coefficient table

Claims

1. Alpha blending means for alpha blending a first image obtained by performing first head shading on a band image which is an image in units of bands, and a second image obtained by performing second head shading on the first image, wherein the alpha blending means switches the coefficient in the alpha blending for each line in the band image An image processing apparatus characterized by the above.

2. Furthermore, The image processing apparatus according to claim 1, further comprising dividing means for dividing an input image into a plurality of band images.

3. Furthermore, The image processing apparatus according to claim 1, further comprising holding means for holding the coefficient in the alpha blending for each line in the band image.

4. Alpha blending means for alpha blending a first image which is an image for each print pass in a band image which is an image in units of bands, and a second image obtained by performing head shading on the first image, wherein the alpha blending means switches the coefficient in the alpha blending for each first image An image processing apparatus characterized by the above.

5. Furthermore, The image processing apparatus according to claim 4, further comprising dividing means for dividing an input image into a plurality of band images and dividing the band images into pass images for each print pass.

6. Furthermore, The image processing apparatus according to claim 4, further comprising holding means for holding the coefficient in the alpha blending for each first image.

7. Furthermore, The image processing apparatus according to any one of claims 1 to 6, further comprising printing means for performing printing based on an image obtained by alpha blending by the alpha blending means.

8. The image processing apparatus according to claim 7, wherein the printing means performs printing by a line head based on an image obtained by alpha blending by the alpha blending means.

9. The image processing apparatus according to claim 7, wherein the printing means performs printing by an LED head based on an image obtained by alpha blending by the alpha blending means.

10. An image processing method performed by an image processing apparatus, The alpha blending means of the image processing apparatus performs alpha blending on a first image obtained by performing first head shading on a band image which is an image in units of bands, and a second image obtained by performing second head shading on the first image. Switch the coefficient in the alpha blending for each line in the band image. An image processing method characterized by the above.

11. An image processing method performed by an image processing apparatus, The alpha blending means of the image processing apparatus performs alpha blending on a first image which is an image for each print pass in a band image which is an image in units of bands, and a second image obtained by performing head shading on the first image. Switch the coefficient in the alpha blending for each first image. An image processing method characterized by the above.

Images