Image processing device

Abstract

To provide an image processing device which can generate printing data that makes the impact position deviation of a droplet due to cross talk of an adjacent nozzle inconspicuous with sample processing without reducing the productivity.SOLUTION: An image processing device comprises: an image data reception unit 30a which receives image data of a printing object; and a printing data generation unit 30b which generates printing data to be printed on a printing medium on the basis of the image data. The printing data generation unit 30b generates printing data for printing a color other than a specific color by reducing the resolution in comparison to the specific color at a position of an impact position deviation pixel of the preset specific color.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an image processing apparatus that generates print data for performing printing using a discharge head in which a plurality of nozzles are arranged.

Background Art

[0002] Conventionally, an inkjet printing apparatus has been proposed that performs printing by discharging ink from an inkjet head onto a printing medium.

[0003] An inkjet head has a plurality of nozzles for discharging ink droplets. For example, in an inkjet head in which a flow path forming a liquid chamber, a vibration member, a nozzle plate, etc. are integrated with adjacent nozzles, when discharging ink droplets from adjacent nozzles, the vibration and deformation of the members constituting the inkjet head affect the discharge of ink droplets from adjacent nozzles, and the discharge speed and discharge amount may change or become unstable.

[0004] Also, in an inkjet head having a partition wall separating each nozzle, the vibration of the partition wall may have an impact, which is generally called crosstalk. In particular, as the density increases in order to achieve both miniaturization and high resolution of the inkjet head, the influence of crosstalk becomes greater.

[0005] When the influence of crosstalk, in which the energy generated during the ink discharge of adjacent nozzles as described above propagates mutually, is large, there is a variation in the discharge speed of the ink droplets and a deviation in the landing position occurs. Also, this deviation in the landing position may become a periodic deviation depending on the printed image, and particularly when the driving frequency is high or when the distance between the inkjet head and the printing medium is large, the deviation tends to be large and noticeable.

[0006] <着弾位置ずれは、印刷画像によっては周期的なずれになる場合があり、特に駆動周波数が速い場合や、インクジェットヘッドと印刷媒体の間が広い場合などはずれが大きく目立つ傾向にある。 As a countermeasure against such misalignment of the projectile's impact position, for example, Patent Document 1 proposes a method that includes multiple drive waveform generation units corresponding to each nozzle and generates correction information for the drive waveform to compensate for fluctuations in discharge characteristics caused by interference. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 6907547 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the method described in Patent Document 1 requires storing discharge history data for each nozzle and correcting the drive waveform of each nozzle based on that discharge history data, which increases the amount of data and data analysis time, resulting in a decrease in productivity.

[0009] In view of the above circumstances, the present invention aims to provide an image processing apparatus capable of generating print data that minimizes the noticeable misalignment of droplet landing positions caused by crosstalk between adjacent nozzles through simple processing, without causing a decrease in productivity. [Means for solving the problem]

[0010] The image processing apparatus of the present invention comprises an image data receiving unit that receives image data to be printed, and a print data generation unit that generates print data for printing on a printing medium based on the image data, wherein the print data generation unit generates print data for printing colors other than the specified color at a lower resolution than the specified color at the positions of pixels with a predetermined offset in the point of impact of a specific color. [Effects of the Invention]

[0011] According to the image processing apparatus of the present invention, printing data is generated to print colors other than the specified color at a lower resolution than the specified color at the positions of pixels with a predetermined misalignment of the droplet's landing position. Therefore, without causing a decrease in productivity, the misalignment of droplet landing positions caused by crosstalk between adjacent nozzles can be made less noticeable with simple processing. [Brief explanation of the drawing]

[0012] [Figure 1] Block diagram showing the schematic configuration of an inkjet printing apparatus using one embodiment of the present invention. [Figure 2] Diagram showing the schematic configuration of the head unit. [Figure 3] Diagram showing the schematic configuration of an inkjet head. [Figure 4] This figure shows an example of a misalignment of the projectile placement occurring when printing a solid image using an inkjet head with two rows of nozzles. [Figure 5] This diagram shows an example of printing a line of a similar color overlaid on the printing start line of a solid K image. [Figure 6] This diagram shows an example where the printing start timing for the solid black (K) image is delayed compared to the original printing start line position for the solid black image. [Figure 7] This diagram shows the relationship between the distance (gap) between the print head and the printing medium, the temperature of the inkjet head, the characteristics of the drive voltage signal supplied to the inkjet head (drive waveform, drive frequency), and the amount of deviation in the impact position. [Figure 8] A diagram showing an example of the waveform of the drive voltage signal. [Figure 9] A diagram showing the drive voltage signal and the change in ejection pressure when ink is ejected from the nozzle in response to that drive voltage signal. [Figure 10] This figure shows an example of a table that correlates the amount of misalignment with the printing conditions for lines of similar color. [Modes for carrying out the invention]

[0013] Hereinafter, an inkjet printing apparatus 1 using an embodiment of the image processing apparatus of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of the inkjet printing apparatus 1 of the present embodiment.

[0014] The inkjet printing apparatus 1 performs printing processing by discharging ink droplets onto a sheet-like printing medium such as paper or film based on image data output from a computer or image data output from a document reading apparatus.

[0015] As shown in FIG. 1, the inkjet printing apparatus 1 includes a head unit 10, a conveyance unit 20, and a control unit 30.

[0016] The head unit 10 includes an inkjet head 35 (corresponding to the discharge head of the present invention) that discharges inks of each color of C (cyan), M (magenta), Y (yellow), and K (black). FIG. 2 is a diagram showing a schematic configuration of the head unit 10 of the present embodiment. As shown in FIG. 2, the head unit 10 of the present embodiment includes a line head 31 that discharges K ink, a line head 32 that discharges C ink, a line head 33 that discharges M ink, and a line head 34 that discharges Y ink. The line heads 31 to 34 extend in a direction orthogonal to the conveyance direction of the printing medium P and are arranged side by side in the conveyance direction of the printing medium.

[0017] Each of the line heads 31 to 34 has two head rows in which three inkjet heads 35 are arranged at equal intervals in a direction orthogonal to the conveyance direction of the printing medium P, and the two head rows are arranged so as to overlap by a predetermined number of nozzles, and six inkjet heads are arranged in a staggered manner.

[0018] Each inkjet head 35 is controlled by the control unit 30 based on image data of each color to discharge ink onto the printing medium P and form a printed image on the printing medium P.

[0019] Figure 3 shows a schematic configuration of one inkjet head 35. As shown in Figure 3, the inkjet head 35 of this embodiment has a plurality of nozzles 36 that eject ink droplets. The plurality of nozzles 36 in each inkjet head 35 are arranged in a direction perpendicular to the transport direction of the printing medium P, and two rows of nozzles, each row of nozzles 36 arranged at equal intervals in the above perpendicular direction, are arranged side by side in the transport direction. As shown in Figure 3, one nozzle row 35a and the other nozzle row 35b are offset by half a pitch of the nozzle spacing in the above perpendicular direction.

[0020] Then, for example, after printing with nozzle row 35a of the inkjet head 35, printing with nozzle row 35b on the same line forms a line. By arranging the dots formed by nozzle row 35b between the dots formed by nozzle row 35a in this way, high-resolution printing becomes possible.

[0021] As the inkjet head 35, for example, a push-type inkjet head can be used that deforms a diaphragm by deforming stacked piezoelectric elements and ejects ink from a nozzle that communicates with the ink flow path. Alternatively, an inkjet head having partitions separating each nozzle may be used.

[0022] The transport unit 20 is equipped with a transport mechanism for transporting the printing medium P. The transport mechanism includes, for example, an annular belt and belt platen rollers, and is configured by stretching the annular belt between belt platen rollers that are arranged to sandwich the head unit 10 in the transport direction of the printing medium P. Then, under the control of the control unit 30, the belt platen rollers rotate, causing the annular belt to move, and thereby transporting the printing medium P that is attracted to the annular belt toward the head unit 10.

[0023] Then, the printing medium P is transported directly beneath the head unit 10, and ink is ejected from each inkjet head 35 of the head unit 10 at predetermined ejection timings, thereby sequentially printing on the transported printing medium P.

[0024] The control unit 30 includes a CPU and semiconductor memory, and controls the entire inkjet printing apparatus 1. The control unit 30 controls the operation of each part of the inkjet printing apparatus 1 by executing a control program pre-stored in a storage medium such as semiconductor memory or a hard disk using the CPU, and by operating electrical circuits.

[0025] Furthermore, the control unit 30 includes an image data receiving unit 30a and a print data generation unit 30b. The control unit 30 operates the image data receiving unit 30a and the print data generation unit 30b by executing an image processing program pre-stored in a storage medium such as a semiconductor memory or a hard disk using a CPU. In this embodiment, the functions of each of the above-mentioned units are realized by executing an image processing program, but this is not limited to this, and some or all of the functions or control may be realized by hardware such as an ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or other electrical circuits.

[0026] The image data receiving unit 30a receives image data output from a computer or document reader.

[0027] The print data generation unit 30b performs various processes on the image data received by the image data receiving unit 30a. Specifically, the print data generation unit 30b converts the RGB image data received by the image data receiving unit 30a into CMYK image data, and then applies halftone processing to the CMYK image data to generate multi-level data with at least three levels. The multi-level data in this embodiment is data that defines the number of ink drops ejected from one nozzle of the inkjet head to form one dot of a printed image, and is hereinafter referred to as ink drop data. Halftone processing methods include halftone processing using the dithering method and halftone processing using the error diffusion method. In this embodiment, the ink drop data corresponds to the print data of the present invention.

[0028] The control unit 30 then outputs drive voltage signals to each inkjet head 35 of the C, M, Y, and K line heads 31-34 based on the ink drop data for each color generated by the print data generation unit 30b, and controls the ejection of ink from each inkjet head 35.

[0029] Furthermore, the control unit 30 controls the transport of the printing medium P by the transport unit 20 and the timing of ink ejection from each inkjet head 35, thereby forming a printed image on the printing medium P according to the image data.

[0030] Here, for example, if the image data includes a solid color pattern, as mentioned above, crosstalk between adjacent nozzles can cause misalignment of ink droplet placement at the start line (first line) of solid color printing, creating gaps in the solid color pattern and leading to a decrease in image quality. A solid color image is an image with a pattern that is continuous for a certain period of time in the transport direction of the printing medium P and in a direction perpendicular to the transport direction.

[0031] Furthermore, the effects of crosstalk between adjacent nozzles often occur at the start line of solid image printing (the first line). From the second line onward, that is, after the ink ejection operation of each nozzle has already begun, crosstalk is less likely to occur because vibrations due to the ink ejection operation continue, and therefore, misalignment of the target position is also less likely to occur.

[0032] Figure 4 shows an example of the impact position misalignment that occurred when printing a solid image using an inkjet head 35 having two rows of nozzles as in this embodiment. In the example shown in Figure 4, the impact position misalignment occurred on the first line of the solid image. In Figure 4, the dots printed by nozzle row 35a of the inkjet head 35 are numbered "1", and the dots printed by nozzle row 35b are numbered "2".

[0033] As shown in Figure 4, for the "1" dots printed by nozzle row 35a, the impact position is shifted in the transport direction between adjacent "1" dots due to the effect of crosstalk between adjacent nozzles. Similarly, for the "2" dots printed by nozzle row 35b, the impact position is shifted in the transport direction between adjacent "2" dots due to the effect of crosstalk between adjacent nozzles.

[0034] As in the inkjet head 35 of this embodiment, when printing one line at high resolution using two rows of nozzles 35a and 35b, the impact position misalignment occurs periodically and is particularly noticeable, as shown in Figure 4.

[0035] Therefore, the control unit 30 of this embodiment performs printing control to make the impact position misalignment of the solid image less noticeable. The printing control to make the impact position misalignment of the solid image less noticeable will be described in detail below.

[0036] The print data generation unit 30b checks whether the image data received by the image data receiving unit 30a contains a solid color image pattern. Methods for checking whether a solid color image is included include checking the data of each pixel constituting the image data, or, if the solid color image contains objects such as shapes, checking the identification information that identifies those objects.

[0037] Then, if the image data contains a solid color image, the print data generation unit 30b identifies the position of the solid color image and generates new ink drop data such that a line of a color other than the color of the solid color image is formed at the print start line of the solid color image.

[0038] Specifically, for example, if the solid color of the image is black (K), the print data generation unit 30b generates new inkdrop data to print lines of a similar color other than black (K). Examples of similar colors other than black include a gray close to black, which is produced by mixing C, M, and Y other than K. Furthermore, when generating inkdrop data for the similar color lines, the print data generation unit 30b generates inkdrop data with a resolution lower than that of the solid image, and increases the amount of ink per dot forming the similar color lines (amount of ink per dot) compared to the amount of ink per dot forming the solid image (amount of ink per dot). Note that if gray ink is used, gray inkdrop data may be generated.

[0039] The control unit 30 then controls the line heads 31-33 based on newly generated C, M, and Y inkdrop data so that the lines of the approximate colors mentioned above are printed over the printing start line of the solid black image.

[0040] Figure 5 shows an example where a line of a similar color, as described above, is printed over the printing start line of a solid black image. The black dots in Figure 5 are the dots that form the solid black image, and the gray dots are the dots that form the line of the similar color. For example, if the resolution of the solid black image is 600 dpi, the resolution of the line of the similar color should be 300 dpi.

[0041] As shown in Figure 5, a misalignment of the projectile's landing position occurs at the start line of the solid K image printing. However, by forming a line of a similar color on top of it using low resolution and increased ink volume, the gap caused by the misalignment can be filled, making it less noticeable. Note that even when printing a line of a similar color, misalignment of the projectile's landing position occurs due to crosstalk between adjacent nozzles, but because the resolution is low and the amount of ink per dot is large, the degree of misalignment is small and not noticeable.

[0042] In this embodiment, we have described an example where only the first line of the solid image printing was misaligned in terms of the impact position. However, if, for example, misalignment occurs in multiple lines, multiple lines of similar colors may be printed as described above.

[0043] The lines where impact position misalignment occurs (the positions of the pixels with impact position misalignment) are predetermined. For example, they are within a range of 1mm to 3mm from the starting edge of the solid image (1 to several lines), and dots of similar color are not formed across the entire solid image.

[0044] Furthermore, although the above embodiment described the case where the solid image is black (K), the same applies when the solid image is of other colors. In this case, new inkdrop data for lines of similar colors other than the solid image color is generated, and the lines of similar colors are printed superimposed on the printing start line of the solid image. Also, even when printing a solid black image using a mixture of K, C, M, and Y, lines of similar colors other than K can be printed superimposed on the printing start line of the solid black image.

[0045] Furthermore, in the above embodiment, a line of a similar color is printed over the printing start line of the solid image. However, in this case, since the printing start line of the solid image and the line of the similar color are printed on top of each other, the density of this area may become darker, which can look unnatural.

[0046] Therefore, the print data generation unit 30b generates ink drop data such that the print start line of the solid image and the print start timing of the approximate color line are offset. The control unit 30 may print only the approximate color line at the position of the original solid image print start line, and for the actual printing of the solid image, after printing the approximate color line, delay the print start timing of the solid image relative to the transport of the printing medium P. Figure 6 shows an example where the print start timing of the solid image K is delayed from the position of the original solid image print start line. The black dots in Figure 6 are dots that form the black solid image, and the gray dots are dots that form the approximate color line. Delaying the print timing means that the print timing is set to a point in time when the transport of the printing medium P has progressed further than the point in time when the printing medium P has been transported to a position where it can be printed at the original printing position relative to the head unit 10. By printing as shown in Figure 6, it is possible to suppress the overlap of the print start line of the solid image and the approximate color line, which would result in increased density.

[0047] Furthermore, as mentioned above, if the start timing of printing a solid image is delayed, after printing one line of a similar color, subsequent lines may also be printed in the same similar color. In addition, when printing subsequent lines of the similar color, ink drop data may be generated that gradually reduces the amount of ink per dot compared to the first line, thereby gradually decreasing the density. This makes the boundary between the printed area of ​​the similar color and the printed area of ​​the solid image less noticeable. Figure 6 shows an example in which a second line of a similar color is printed over the first line of a solid image, with a reduced density.

[0048] Furthermore, for example, when printing a solid K image, even when printing a color other than K at low resolution across the entire solid image to increase the density, when printing lines of a color other than K on top of the starting line of the solid K image, the amount of ink per dot should be increased compared to the amount of ink per dot used when printing other lines of that color. Note that in this case, the line for which the amount of ink per dot is increased is not limited to just one line. If there are multiple lines with misaligned landing positions, the amount of ink for multiple lines may be increased. Also, when printing multiple lines, the amount of ink for the second line onwards may be gradually reduced to its original value (gradually approaching the amount of ink for the other lines).

[0049] In the above description of the embodiment, the position of a solid image in the image data was identified, and a line of a similar color was formed at the printing start line of that solid image. However, it is not limited to solid images; any image pattern that causes a misalignment of the impact point can be used. The control unit 30 can identify the location in the image where the misalignment of the impact point occurs and generate inkdrop data that forms a line of a similar color at that location.

[0050] Furthermore, the amount of misalignment of the landing point due to crosstalk between adjacent nozzles varies depending on the distance (gap) between the head unit 10 and the printing medium P, the characteristics of the drive voltage signal supplied to the inkjet head 35, and the temperature of the inkjet head 35. Therefore, depending on the amount of misalignment, ink drop data may be generated that changes the amount of ink per dot or the number of lines of similar color when printing lines of similar color. Specifically, the amount of ink per dot may be increased, the number of lines of similar color may be increased, or both the amount of ink per dot and the number of lines of similar color may be increased as the amount of misalignment increases.

[0051] FIG. 7 is a diagram showing the relationship between the distance (gap) between the head unit 10 and the printing medium P, the temperature of the inkjet head 35, and the characteristics (drive waveform, drive frequency) of the drive voltage signal supplied to the inkjet head 35, and the amount of deviation of the landing position shift. The magnitude relationship of the deviation amounts from deviation amount 1 to deviation amount 5 is deviation amount 1 < deviation amount 2 < deviation amount 3 < deviation amount 4 < deviation amount 5.

[0052] Also, gap 1 and gap 2 shown in FIG. 7 are the distances between the head unit 10 and the printing medium P, and gap 1 < gap 2. The larger the distance (gap), the larger the deviation amount. This is because the flight distance of the ink droplets becomes longer.

[0053] Also, temperature t1, temperature t2, and temperature t3 shown in FIG. 7 are the temperatures of the inkjet head 35, and t1 < t2 < t3. Since the higher the temperature of the inkjet head 35, the lower the ink viscosity, it is difficult to suppress the vibration caused by the ejection of ink droplets from adjacent nozzles, and the change in the ejection speed of the ink droplets becomes larger, so the deviation amount becomes larger.

[0054] Furthermore, frequencies 1, 2, and 3 shown in Figure 7 are the drive frequencies of the drive voltage signals supplied to each nozzle of the inkjet head 35, with frequency 1 < frequency 2 < frequency 3. Figure 8 shows an example of the waveform of the drive voltage signal. When the voltage value of the drive voltage signal changes from V1 to V2, one drop of ink is ejected from the nozzle. Therefore, when multiple ink droplets are ejected continuously from one nozzle, multiple drive voltage signals with the waveform shown in Figure 8 are supplied to the nozzle in succession. The drive frequency of the drive voltage signal is the frequency based on the interval from when an ink droplet is ejected from a predetermined nozzle until ejection starts again from the same nozzle. In other words, it is the frequency based on the interval from when one or more drive voltage signals with the waveform shown in Figure 8 are supplied to a predetermined nozzle in succession until the drive voltage signal is supplied to the same nozzle again. Furthermore, the higher the resolution of printing in the transport direction of the printing medium P, the higher the drive frequency becomes, and the more ink droplets need to be ejected per unit time, so the amount of ink per ink droplet decreases. When the amount of ink per ink droplet decreases, the effect of vibration due to crosstalk on the ink droplet increases, resulting in a larger displacement.

[0055] Furthermore, the drive waveforms w1, w2, and w3 shown in Figure 7 represent the length of the drive voltage signal waveform. In the case of the drive voltage signal waveform shown in Figure 8, the waveform length is the length of the range A. Note that the drive frequency does not change even if the drive waveform changes. Each inkjet head 35 has a waveform suitable for ink ejection, and the waveform of the drive voltage signal may be changed for each inkjet head 35.

[0056] When the waveform of the drive voltage signal changes, the phase of the waveform of the ejection pressure when ink is ejected from the nozzle changes. Figure 9 shows the drive voltage signal and the change in ejection pressure when ink is ejected from the nozzle due to that drive voltage signal. The ejection pressure is greatest when the voltage of the drive voltage signal changes from V1 to V2, and at this time the ink is ejected from the nozzle. After that, the ejection pressure gradually decreases, but the residual vibration caused by this pressure change propagates to adjacent nozzles, causing crosstalk.

[0057] Furthermore, when the phase of the discharge pressure waveform shown in Figure 9 changes, the phase of the residual vibration propagating to adjacent nozzles also changes. For example, if ink is discharged from an adjacent nozzle at the timing of the peak of the residual vibration waveform, the effect of crosstalk is significant, and the amount of deviation becomes large. Conversely, if ink is discharged from an adjacent nozzle at the timing when the amplitude of the residual vibration waveform is small, the effect of crosstalk is small, and the amount of deviation becomes small. In other words, the effect of crosstalk and the amount of deviation change depending on the waveform of the drive voltage signal.

[0058] The relationship between drive waveforms w1, w2, and w3 shown in Figure 7 is drive waveform w1 < drive waveform w2 < drive waveform w3. However, in this embodiment, the amount of deviation is large for drive waveform w2, and the amount of deviation is small for drive waveforms w1 and w3.

[0059] The print data generation unit 30b then acquires information on the distance (gap) between the head unit 10 and the printing medium P, the temperature of the inkjet head 35, and the characteristics of the drive voltage signal supplied to the inkjet head 35 (drive waveform, drive frequency). Based on this acquired information, it calculates the amount of misalignment by referring to Figure 7, and generates inkdrop data for printing the approximate color lines described above based on the calculated amount of misalignment. This makes it possible to print lines of approximate color according to the amount of misalignment based on the distance (gap) between the head unit 10 and the printing medium P, the temperature of the inkjet head 35, and the characteristics of the drive voltage signal supplied to the inkjet head 35, thereby appropriately filling the gap caused by misalignment of the impact point.

[0060] Specifically, the control unit 30 has a table set up that associates the amount of misalignment shown in Figure 10 with the printing conditions (ink amount and number of lines) for printing lines of similar color. The print data generation unit 30b, based on the amount of misalignment obtained by referring to Figure 7, refers to the table in Figure 10 to determine the printing conditions (ink amount and number of lines) for printing lines of similar color. The relationship of ink amounts shown in Figure 10 is ink amount 1 < ink amount 2 < ink amount 3 < ink amount 4 < ink amount 5. Also, line number 1 shown in Figure 8 means that there is 1 line to print with the similar color, and line number 2 means that there are 2 lines to print with the similar color.

[0061] The print data generation unit 30b generates ink drop data for lines of similar colors according to the amount of ink and number of lines determined by referring to Figure 10.

[0062] Although not considered in Figure 7, the voltage values ​​of the drive voltage signal (V2-V1 shown in Figure 8) may also be taken into consideration when changing the printing conditions for the approximate color lines. As the voltage value of the drive voltage signal decreases, the flight speed of the ink droplets ejected from the nozzle decreases, resulting in a larger amount of misalignment. Therefore, the control unit 30 should increase the amount of ink or the number of lines for the approximate color lines as the voltage value of the drive voltage signal decreases.

[0063] The distance (gap) between the head unit 10 and the printing medium P, the temperature of the inkjet head 35, and the characteristics of the drive voltage signal supplied to the inkjet head 35 (drive waveform, drive frequency, voltage value) are set and input by the user using a predetermined input unit (not shown), and this set information is acquired by the control unit 30. As the input unit, for example, an operation panel consisting of a touch panel provided on the inkjet printing device 1 can be used.

[0064] Furthermore, in this embodiment, the amount of displacement is determined using a table as shown in Figure 7, but a function for calculating the amount of displacement may be set in advance, and the amount of displacement may be calculated using that function.

[0065] Furthermore, regarding the temperature of the inkjet head 35, a temperature detection unit (not shown) such as a temperature sensor may be provided to the inkjet printing apparatus 1, and the control unit 30 may acquire the temperature detected by the temperature detection unit. The temperature detected by the temperature detection unit may be the temperature of the inkjet head 35, the ambient temperature, or the temperature of the ink supplied to the inkjet head 35.

[0066] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the embodiments described above. For example, all the components shown in the embodiments may be combined as appropriate. It goes without saying that various modifications and applications are possible without departing from the spirit of the invention.

[0067] The following further notes are disclosed regarding the present invention. (Note)

[0068] In the printing apparatus of the present invention, the print data generation unit can generate print data such that the printing start position of a specific color is offset from the printing start position of colors other than that specific color.

[0069] Furthermore, in the printing apparatus of the present invention, when the printing data generation unit generates printing data for printing colors other than a specific color, it can increase the amount of droplets per dot of the color other than the specific color compared to the amount of droplets per dot of the specific color.

[0070] Furthermore, in the printing apparatus of the present invention, the print data generation unit can generate print data in which the printing conditions for colors other than a specific color differ depending on the distance between the printing medium and the head unit having an ejection head that ejects liquid droplets onto the printing medium to perform printing.

[0071] In the printing apparatus of the present invention, the print data generation unit can generate print data with different printing conditions for colors other than a specific color, depending on the temperature of the ejection head. [Explanation of symbols]

[0072] 1. Inkjet printing device 10 Head section 20 Conveying section 30 Control Unit 30a Image Data Reception Section 30b Print Data Generation Unit 31-34 Line Head 35 Inkjet Heads 35a, 35b Nozzle Rows 36 nozzles P Print media

Claims

1. An image data receiving unit that receives image data to be printed, The system includes a print data generation unit that generates print data for printing on a printing medium based on the aforementioned image data, Image processing apparatus wherein the print data generation unit prints colors other than the specified color at a lower resolution than the specified color at the positions of pixels with a predetermined offset in the point of impact of a specific color, and generates print data in which the amount of droplets per dot of the colors other than the specified color is increased compared to the amount of droplets per dot of the specified color.

2. The image processing apparatus according to claim 1, wherein the print data generation unit generates print data such that the print start position of the specific color and the print start position of colors other than the specific color are offset.

3. An image data receiving unit that receives image data to be printed, The system includes a print data generation unit that generates print data for printing on a printing medium based on the aforementioned image data, The image processing apparatus generates print data in which the print data generation unit prints colors other than the specified color at a lower resolution than the specified color at the positions of pixels with a predetermined offset in the point of impact of a specific color, and generates print data in which the printing conditions for colors other than the specified color differ depending on the distance between the printing medium and the head unit having an ejection head that ejects droplets onto the printing medium to perform printing.

4. An image data receiving unit that receives image data to be printed, The system includes a print data generation unit that generates print data for printing on a printing medium based on the aforementioned image data, The image processing apparatus generates print data in which the print data generation unit prints colors other than the specified color at a lower resolution than the specified color at the positions of pixels with a predetermined offset in the point of impact of a specific color, and generates print data in which the printing conditions for colors other than the specified color differ according to at least one of the drive waveform, drive frequency, and drive voltage of the ejection head that ejects droplets onto the printing medium to print.

Images