JP2013102397A - Image processing apparatus, image processing method, and image processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus and the like for printing capable of separately adjusting color and black, and appropriately responding user's needs related to density adjustment by executing density adjustment in which a color material amount is controllable depending on the density.SOLUTION: An image processing apparatus connectable to an image recording apparatus comprises: a color conversion part which converts image data expressed in a first color space into color material amount data expressed in a second color space of a color material used in the image recording apparatus; a density adjustment part which increases or decreases the color material amount data on the basis of the specified adjustment value; a dot decomposition part which converts the color material amount data increased or decreased into dot generation rate data expressed in a dot generation rate dependent on a size of dots formed in the image recording apparatus; and a halftone processing part which converts the dot generation rate data into data in which presence/absence of formed dots is expressed.

Description

  The present invention relates to an image processing apparatus for printing and the like, and in particular, it is possible to adjust color and black separately and execute density adjustment that can control the amount of color material according to the density, so that the user needs for density adjustment can be accurately met. The present invention relates to an image processing apparatus and the like that can meet the requirements.

  Conventionally, printers such as inkjet printers are used for various purposes. In the printer, printing is executed by forming dots by driving a color material onto a printing medium such as paper. Such print processing requires image processing for converting image data to be printed into data representing the presence or absence of dots, and the image processing is performed by a driver in a host device or a printer controller.

  Further, in the image processing, density adjustment processing based on a user request or the like may be performed. As a conventional density adjustment method, as described in Patent Document 1 below, the density of each color included in image data is set as follows. There is one that converts the density according to the set adjustment value. In addition, as described in Patent Documents 2 and 3 below, density adjustment by undercolor removal is often used.

JP 2009-141941 A JP 2006-279922 A JP 2008-205964 A

  However, as described above, when the density adjustment process is performed on the image data, if the color expression of the processed data is different from the color expression by the color material used in the printer, the density increase / decrease by the density adjustment process is As such, the amount of the color material to be printed on the printing medium is not increased or decreased, and in some cases, the increase or decrease may be reversed. For example, when the color material used in the printer is CMYK (cyan, magenta, yellow, black) and the image data is expressed in RGB (red, green, blue), conversion from RGB to CMYK is Since it is not determined uniformly, the change in the color material amount due to the density increase / decrease can have various results depending on the design of the conversion content. Specifically, as an example, the density is 10% with respect to data expressed in RGB (0, 0, 0) (data expressing the density of each color in 256 gradations and corresponding to black). When the adjustment process is performed, the data becomes (20, 20, 20), and then data expressed in CMYK (for example, data expressed by the color material coverage per unit area proportional to the amount of the color material) ), The value becomes (10%, 10%, 10%, 75%). However, when the original RGB (0, 0, 0) is converted as it is, it becomes CMYK (0%, 0%, 0%, 100%), and the result of the above density adjustment is that the density is reduced by 10%. Regardless, the result is that the amount of the color material increases (100% (K) → 105% (CNYK total)).

  The purpose of density reduction in density adjustment includes prevention of back-through and bleeding on paper (printing medium) and reduction of ink (coloring material) cost used for printing. Although it is necessary to reduce not only the density of the color material but also the amount of the color material to be physically applied, in the above-described situation, it is difficult to adjust because it is impossible to grasp the specific color material reduction amount.

  In addition, the purpose of increasing the density in the density adjustment is to eliminate the so-called “insufficient” situation in the printing result. An increase needs to be obtained, and such an objective cannot be realized in the situation described above.

  Further, the above-described conventional technique using undercolor removal is a technique in which color ink is replaced with black ink, and there is a problem that it is difficult to separately adjust color and black.

  For example, when the purpose of reducing the total ink ejection amount by a specified amount without degrading the quality of black characters, barcodes, etc. and without increasing the black ink, a method using the above under color removal It is difficult.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is an image processing apparatus for printing, in which color and black can be adjusted separately and density adjustment capable of controlling the amount of color material according to the density is executed, and the user needs for density adjustment It is to provide an image processing apparatus and the like that can appropriately meet the requirements.

  In order to achieve the above object, according to one aspect of the present invention, an image processing device connectable to an image recording device uses image data expressed in the first color space as a color material used in the image recording device. A color conversion unit that converts the color material amount data expressed in the second color space, a density adjustment unit that increases or decreases the color material amount data based on a specified adjustment value, and the color material amount data after the increase or decrease Is converted into dot generation amount data expressed by the dot generation amount for each dot size formed by the image recording apparatus, and the dot generation amount data represents the presence or absence of the dot formation. A halftone processing unit that converts the data into data.

  Further, in the above invention, a preferable aspect is that the adjustment value is separately specified for chromatic color and black, and the density adjustment unit is configured to use the color material of chromatic color based on the adjustment value specified for chromatic color. The amount data is increased or decreased, and the black color material amount data is increased or decreased based on the adjustment value specified for black.

  Furthermore, in the above invention, a preferable aspect is a table in which the image data and the color material amount data are associated with each other so that a total color material amount of the color material is within a limit value, and the limit value A plurality of color conversion tables different from each other, and the color conversion unit selects the color conversion table based on the designated adjustment value, and performs the conversion using the selected color conversion table. And

  Furthermore, in the above invention, according to one aspect, the color conversion unit is configured such that, when the designated adjustment value indicates an increase in density, the color conversion table having the limit value larger than the reference color conversion table. It is characterized by selecting.

  Furthermore, in the above-described invention, a preferable aspect is that the density adjusting unit selects the color conversion table having a large limit value, so that the color material amount data generated by the conversion processing by the color converting unit is the specified data. When the adjusted value becomes an increased value exceeding the concentration increase, the excess is decreased.

  Further, in the above invention, according to one aspect, the color conversion unit is configured to calculate a total color material amount of the color material amount data obtained after processing by the density adjustment unit when the reference color conversion table is used. When the maximum value does not exceed the limit value of the reference color conversion table, the reference color conversion table is selected.

  In order to achieve the above object, another aspect of the present invention provides an image processing method in which image data expressed in a first color space is converted into color expressed in a second color space of a color material used for printing. A color conversion step for converting the color material amount data; a density adjustment step for increasing / decreasing the color material amount data based on a designated adjustment value; A dot decomposition step for converting the dot generation amount data expressed by the generation amount of dots by size, and a halftone processing step for converting the dot generation amount data into data expressing the presence or absence of the dot formation. That's it.

  In order to achieve the above object, according to still another aspect of the present invention, there is provided a color conversion step in which an image processing program converts image data for printing into color material amount data expressed by the amount of color material used for printing. And a density adjustment step for increasing / decreasing the color material amount data based on a specified adjustment value, and converting the increased / decreased color material amount data into dot generation amount data expressed by dot generation amount for each dot size. And causing the image processing apparatus to execute a dot separation step and a halftone processing step of converting the dot generation amount data into data expressing the presence or absence of dots.

  Further objects and features of the present invention will become apparent from the embodiments of the invention described below.

1 is a configuration diagram according to an embodiment of an image processing apparatus to which the present invention is applied. 5 is a diagram illustrating a dot separation table 128. FIG. 3 is a flowchart illustrating a procedure of processing performed by a driver 12. It is the figure which illustrated the density adjustment input screen. It is the figure which showed the transition of the data in a 1st specific example. It is a figure showing change of data in the 2nd example. It is a figure showing change of data in the 3rd example. It is the figure which illustrated the result of the dot separation process in the 3rd example. It is the flowchart which illustrated the procedure of the image processing in a modification. It is the figure which illustrated transition of data in a modification.

  Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention. In the drawings, the same or similar elements are denoted by the same reference numerals or reference symbols.

  FIG. 1 is a configuration diagram according to an embodiment of an image processing apparatus to which the present invention is applied. The host computer 1 shown in FIG. 1 is an image processing apparatus to which the present invention is applied, and the density adjustment unit 123 performs density adjustment processing (color material) after the color conversion unit 122 performs density adjustment processing specified by the user. (Quantity data) is separately executed for black (black) and color (chromatic color). With this apparatus, color and black can be adjusted separately, and density adjustment that can control the amount of color material according to the density is executed, and it is possible to appropriately meet the user needs related to density adjustment.

  In FIG. 1, the apparatus configuration in the present embodiment is functionally shown. The host computer 1 is a host device of the printer 2 that gives a print instruction to the printer 2 (image recording apparatus), and is configured by, for example, a personal computer. Therefore, although not shown, the host computer 1 includes a CPU, RAM, ROM, HDD, display, operation device, and the like.

  The application 11 is a print request source, and there may be applications having various functions such as a text creation application and a graphic creation application. The application 11 includes a program that instructs processing contents, the CPU that executes processing according to the programs, the RAM, and the like, and outputs image data representing the printing contents when a print request is made.

  The driver 12 is a driver for the printer 2, performs image processing on the image data output from the application 11 to obtain image data (print data) for the printer 2, sends the print data to the printer 2, and This is a part that issues a print instruction for printing requested by the application 11.

  The driver 12 includes a driver program for instructing processing contents, the CPU for executing processing according to the program, various data used for processing, the RAM, and the like. The specific functional configuration and processing contents will be described later. . The driver program is stored in the HDD of the host computer 1 by being copied from a storage medium such as a CD to the host computer 1 or downloaded to the host computer 1 via a network such as the Internet. The

  The printer 2 is, for example, a line head ink jet printer that executes print processing in accordance with the print instruction of the host computer 1. As shown in FIG. 1, the printer 2 includes a controller 13 and a print execution unit 14.

  The controller 13 is a part that receives print data according to the print instruction and causes the print execution unit 14 to execute print processing according to the print data. Specifically, it is configured by a program describing processing contents, a CPU that executes processing according to the program, a RAM, a ROM that stores the program, an ASIC, and the like.

  The print execution unit 14 is a part that actually executes print processing on a print medium such as paper in accordance with an instruction from the controller 13. Here, a line head including a plurality of nozzles that eject ink that is a color material to the print medium, a transport device that transports the print medium at a predetermined speed, and the like are provided. Here, as an example, CMYK (cyan, magenta, yellow, black) four color inks are used as color materials, and ink is ejected from the respective nozzles corresponding to the respective colors. Then, printing is performed by ejecting the ejected ink into the printing medium to form dots. Moreover, the line head is divided into a plurality of head units as an example, and these are alternately arranged in a so-called zigzag pattern.

  Next, the functional configuration of the driver 12 shown in the lower part of FIG. 1 will be described. The rasterizing unit 121 performs rasterization processing on the image data output from the application 11 and outputs bitmap data expressed in a first color space, for example, an RGB (red, green, blue) color space. This is the part to be generated.

  The color conversion unit 122 converts the bitmap data into data expressed in a CMYK color space that is a color space (second color space) of the color material, that is, ink amount data in accordance with the color conversion table 127. is there.

  The color conversion table 127 is a LUT (lookup table) prepared in advance, and for each density gradation value of RGB (for example, a value expressed by 256 gradations from 0 to 255), a corresponding CMYK It is a table in which each ink amount data is stored. Here, the ink amount data is data expressing the coverage with the color material per pixel, and is proportional to the ink amount. The ink amount data can also be expressed by ink weight or volume. The color conversion table 127 is designed for printing conditions such as the type of printing medium (paper type) and resolution, and is stored in the HDD or the like. Here, as an example, three color conversion tables 127 (1), 127 (2), and 127 (3) are prepared, and are positioned in order for low density, medium density, and high density, respectively. Specifically, when the total amount of ink amount data of all color materials (CMYK) is the total ink ejection amount, the limit value (maximum value) is set for low density, medium density, and high density. Designed to be 120%, 160%, and 200%, respectively, in order. Therefore, regardless of the value of the image data before color conversion, the total amount of ink amount data (total color material amount of the color material) as a result of processing using each color conversion table 127 is the total ink amount. The limit value (maximum total ink ejection amount) of the ejection amount is not exceeded.

  The color conversion unit 122 includes an LUT selection unit 122a that selects the plurality (three) of color conversion tables 127. The LUT selection unit 122a selects an appropriate color conversion table 127 according to the printing conditions and the density adjustment request by the user during the color conversion process, and the color conversion process is performed by the selected color conversion table 127.

  Each color conversion table 127 is generated in advance by a conventional method and stored in the same manner as the driver program described above.

  Next, the density adjustment unit 123 is a part that executes density adjustment processing on the ink amount data after the color conversion processing. The density adjusting unit 123 executes a process of separately changing the color (CMY) ink amount data and the black (K) ink amount data in accordance with the density adjustment value designated by the user.

  Next, the dot separation unit 124 is a part that converts the ink amount data after the density adjustment into data expressed by dot generation amounts according to the dot separation table 128. Here, as an example, there are three sizes, small dots (S), medium dots (M), and large dots (L), that can be formed on the print medium by ejecting ink from each nozzle. The ink amount data (0% -100%) is converted into the data of the generation amount of these three dots. Here, the generation amount of each dot is represented by a numerical value obtained by dividing the pixel into a mesh and arranging the dots in the divided area, and can be represented by a value from 0 to 4096, for example.

  The dot separation table 128 is a table in which the generated amounts of the three dots are associated with CMYK ink amount data (0% -100%), and is stored in the HDD or the like. The storage method is the same as that of the driver program described above.

  FIG. 2 is a diagram illustrating the dot separation table 128 in a graph format. In the graph shown in FIG. 2, the horizontal axis represents the ink amount (data) before the dot separation, and the vertical axis represents the dot generation amount after the dot separation. Graphs S, M, and L show the generation amounts of small dots, medium dots, and large dots, respectively. As can be seen from the figure, when the amount of ink is small, only small dots are generated, resulting in low density printing. Conversely, when the amount of ink is large, three dots including large dots are generated and the density is reduced. High printing will be realized.

  Next, the halftone processing unit 125 is a part that performs so-called halftone processing and converts the data converted into the dot generation amount into data representing the presence / absence of formation of each dot. As a processing method, a conventional dither method, an error diffusion method, or the like can be used.

  Next, the print data conversion unit 126 is a part that converts the data after the halftone process into the print data expressed by a command for the printer 2.

  In the driver 12 in the present embodiment having the configuration as described above, image processing is executed as follows. FIG. 3 is a flowchart illustrating a procedure of processing performed by the driver 12. Hereinafter, specific contents of the image processing will be described with reference to FIG.

  First, when the user using the application 11 executes a print request operation as described above and executes a density adjustment request operation, the driver 12 receives the density adjustment request (step S1). Upon receiving the request, the driver 12 displays a density adjustment input screen on the display device of the host computer 1 (step S2).

  FIG. 4 is a diagram illustrating the density adjustment input screen. On the input screen, the user can separately instruct the density adjustment for color and black. The color density adjustment can be performed by operating the slide bar indicated by a in FIG. Each is instructed by operating the slide bar indicated by b in the figure. For example, an instruction is given such that both are 30% darker (+ 30%, + 30%), or the color is 30% thinner and the black is 10% thinner (OLE_LINK1OLE_LINK2-30%, OLE_LINK1OLE_LINK2-10%).

  When the user performs an input operation on the displayed input screen as described above, the input density adjustment value (the values of the two density adjustment ratios (%) input by the slide bar) and the application 11 are displayed. The image data to be printed from is received by the driver 12 (step S3).

  At this stage, the received image data is usually in a data format expressed in units of objects such as text, graphics, and images. Therefore, the rasterizing unit 121 executes rasterization processing and converts the image data into Conversion into bitmap data (step S4). Specifically, the rasterizing unit 121 converts each pixel into data having density gradation values (0-255) of RGB colors. A conventional method can be used for rasterization.

  Next, the generated bitmap data is transferred to the color conversion unit 122, and color conversion processing using the color conversion table 127 described above is executed. Specifically, first, the LUT selection unit 122a selects the color conversion table 127 corresponding to the printing conditions included in the image data or the color conversion table 127 determined as a default as a reference table.

  Next, the LUT selection unit 122a determines whether or not the received density adjustment value means an adjustment for increasing the density (the density adjustment ratio is positive) (step S5). If not, that is, if the density adjustment is not performed, or if the density adjustment value means an adjustment for decreasing the density (the density adjustment ratio is negative) (No in step S5), the above In order to perform the process using the selected reference color conversion table 127, the process proceeds to step S8.

  On the other hand, when the density adjustment value means an adjustment for increasing the density (Yes in step S5), the LUT selection unit 122a switches the color conversion table 127 to be used (step S6). Specifically, the selected color conversion table is switched to a color conversion table 127 for higher density than the reference table. More specifically, it is equal to or greater than the value (X × (1 + Y% / 100%)) obtained by multiplying the maximum total ink ejection amount (X) of the reference table by the larger value (+ Y%) of the density adjustment value. The color conversion table 127 having the maximum total ink ejection amount is switched.

Thereafter, the color conversion unit 122 obtains the amount of density reduction required by switching the table (step S7). Specifically, it is calculated by the following formulas (1) and (2).
Color density reduction (%) = (X × (1 + Y1 / 100) / Z−1) × 100 (1)
Black density reduction amount (%) = (X × (1 + Y2 / 100) / Z−1) × 100 (2)
X is the maximum total ink ejection amount (%) of the reference table, Y1 is the color density adjustment value (%), Y2 is the black density adjustment value (%), and Z is This is the maximum total ink ejection amount (%) in the color conversion table 127 after the switching.

  Next, the color conversion unit 122 uses the color conversion table 127 selected at that time, that is, if the density adjustment is not increased, if the density adjustment is increased by using the above-described reference table. Executes color conversion processing using the table after the switching (step S8). Specifically, the color conversion unit 122 refers to the color conversion table 127 and converts the data represented by (R, G, B) of each pixel of the generated bitmap data in the color conversion table 127. The data is sequentially converted into (C, M, Y, K) values associated with the data values, and ink amount data in which each pixel is expressed by the ink amount of each color of CMYK is generated.

  In this way, when the color conversion process is executed, the generated ink amount data is transferred to the density adjustment unit 123, where the density adjustment process is executed (steps 9 and 10). Specifically, for each color (CMY) ink amount and black (K) ink amount, a process of decreasing the density (reducing the value) is executed. More specifically, with respect to the ink amount data, for each pixel, the CMY values are reduced according to the color density reduction rate, and the K values are reduced according to the black density reduction rate. To do. Here, the density reduction ratio of color and the density reduction ratio of black are density adjustment values inputted by the user when the density adjustment designated by the user is not increased, and the density designated by the user. When the adjustment is an increase, the color density reduction amount and the black density reduction amount obtained in step S7.

  Next, (C ′, M ′, Y ′, K ′), which is ink amount data after density adjustment, is transferred to the dot separation unit 124, and the separation processing for each dot is performed on the data after adjustment. It is executed (step S11). The processing is performed by the dot separation unit 124 using the dot separation table 128 described above. Specifically, referring to the dot separation table 128, (C ′, M ′, Y ′, K ′) for each pixel. The ink amount data is converted into the generated amount data (S, M, L) for each dot.

  Thereafter, the converted data is transferred to the halftone processing unit 125, where halftone processing is executed (step S12). Then, the dot generation amount data (S, M, L) of each color of each pixel is converted into data representing the presence / absence (on / off) of small, medium, and large dots.

  The halftone processed data is converted into print data (command) for the printer 2 by the print data conversion unit 126 (step S13) and transmitted to the printer 2 (step S14). Thereafter, the transmitted print data is received by the controller 13 and a printing process according to the print data is executed. That is, ink is ejected from each nozzle according to print data, and small, medium, and large dots are formed on the print medium. Then, printing is realized with an ink amount that reflects the density adjustment specified by the user.

  Next, a specific example of the portion relating to the density adjustment of the image processing described above will be described. FIG. 5 is a diagram showing data transition in the first specific example. In the first specific example, as shown in FIG. 5 (1), the density adjustment value designated by the user and received in step S3 is + 50% for color and + 10% for black. Show.

  Further, as shown in (2) of FIG. 5, the values of (R, G, B), which are image data of the pixel of interest as an example, are (200, 150, 150), and (3) of FIG. As shown, the table selected as the reference table by the LUT selection unit 122a is a color conversion table 127 (1) (here, LUT1) having a maximum total ink ejection amount of 120%.

  In the first specific example, since the designated density adjustment is an increase, switching of the color conversion table 127 is executed according to step S6 described above, as shown in (4) and (5) of FIG. The color conversion table 127 (3) (here, LUT3) having a maximum total ink ejection amount 200% exceeding a value 180% obtained by enlarging the maximum total ink ejection amount 120% of LUT1 with the larger density adjustment value 50%. Is selected as the table after switching.

  After that, as shown in (6) of FIG. 5, the color and black density reduction amounts are calculated by the process of step S7. As a result, the color density reduction amount is -10%, and the black density reduction amount is -34%.

  After that, as shown in (7) of FIG. 5, the color conversion process by the selected LUT 3 is executed by the process of step S8, and CMYK ink amount data is generated. The ink amount data of the target pixel is (C, M, Y, K) = (0%, 50%, 50%, 33%).

  Next, as shown in FIG. 5 (8), density adjustment (decrease) is performed for the color ink amount of the target pixel by the process of step S9. Each ink amount data of (C, M, Y) = (0%, 50%, 50%) is reduced by 10% according to the obtained density reduction amount−10%, and (C ′, M ′, Y ') = (0%, 45%, 45%).

  Similarly, by the process of step S10, as shown in (9) of FIG. 5, the density adjustment (decrease) process is performed for the black ink amount of the target pixel. The ink amount data of K = 33% decreases by 34% in accordance with the obtained density reduction amount−34%, and K ′ = 22%.

  In this way, the density adjustment process in the first specific example is executed. In the first specific example, the color conversion table 127 is switched by increasing the density, and the amount that has been increased by the switching is adjusted later.

  Next, a second specific example will be described. FIG. 6 is a diagram showing data transition in the second specific example. In the second specific example, as shown in (1) of FIG. 6, the density adjustment value designated by the user and received in step S3 is + 30% for color and + 30% for black. Show.

  Moreover, as shown in (2) of FIG. 6, the value of (R, G, B) of the pixel of interest as an example is (100, 100, 100), and as shown in (3) of FIG. The table selected as the reference table by the LUT selection unit 122a is the color conversion table 127 (2) (here, LUT2) having a maximum total ink ejection amount of 160%.

  In the second specific example, since the designated density adjustment is an increase, switching of the color conversion table 127 is executed in accordance with step S6 described above, as shown in (4) and (5) of FIG. A color conversion table 127 (3) (here, LUT3) having a maximum total ink ejection amount of 200% from a value 208% obtained by enlarging the maximum total ink ejection amount 160% of LUT1 with a density adjustment value of 30%. It is selected as the table after switching. As described above, when there is no color conversion table 127 having the maximum total ink ejection amount exceeding the enlarged value, the color conversion table 127 having the maximum maximum total ink ejection amount is selected.

  Thereafter, as shown in (6) of FIG. 6, the color and black density reduction amounts are calculated by the process of step S7. However, in such a case, since an excessive increase is not made by switching the table, the color density reduction amount and the black density reduction amount are set to 0%. In the case of this example, there is no significant difference between the enlarged value 208% and the maximum total ink ejection amount 200% of the LUT 3, so that the density adjustment desired by the user can be realized.

  After that, as shown in FIG. 6 (7), the color conversion processing by the selected LUT 3 is executed by the processing in step S8, and CMYK ink amount data is generated. The ink amount data of the target pixel is (C, M, Y, K) = (50%, 50%, 50%, 50%).

  Next, the density adjustment (decrease) process is performed for the color ink amount of the target pixel by the process of step S9. However, since the color density decrease amount is 0% as described above, (8) in FIG. ), The ink amounts of (C, M, Y) = (50%, 50%, 50%) remain unchanged.

  Similarly, the density adjustment (decrease) process is performed for the black ink amount of the target pixel by the process of step S10. However, since the black density decrease amount is 0% as described above, (9 in FIG. 6). ), The ink amount of K = 50% is left as it is.

  In this way, the density adjustment process in the second specific example is executed. In the second specific example, the color conversion table 127 is switched by increasing the density. However, since there is no excessive increase due to the switching, the subsequent adjustment processing is not performed.

  In the second specific example, if the density adjustment (increase) is performed on the RGB values of the image data, (R, G, B) = (100, 100, 100) of the pixel of interest is The ink amount data obtained by adjusting to (R ′, G ′, B ′) = (50, 50, 50) and the subsequent color conversion processing is (C, M, Y, K) = (20%, 20%). , 20%, 70%). On the other hand, when (R, G, B) = (100, 100, 100) without density adjustment is color-converted with the same table, (C, M, Y, K) = (35%, 35%, 35 %, 45%). The total ink ejection amount of both is 150% when the density adjustment is not performed, and 130% when the density adjustment is performed. Therefore, in spite of instructing the density increase, the ink amount is decreased.

  Further, in the second specific example, when the process of simply increasing the ink amount after the color conversion process is performed as instructed without switching the color conversion table 127, (C, M, Y, K) = (40%, 40%, 40%, 40%) ink amount data is obtained, and then each ink amount is increased by 30%. Therefore, the ink amount data after density adjustment is (C ′ , M ′, Y ′, K ′) = (52%, 52%, 52%, 52%). In this case, the total ink ejection amount is 208%, which exceeds the maximum total ink ejection amount 200% of the high density LUT 3. This is because ink that exceeds the design limit is applied, which is not preferable from the viewpoint of bleeding and show-through.

  Next, a third specific example will be described. FIG. 7 is a diagram showing data transition in the third specific example. In the third specific example, as shown in (1) of FIG. 7, the density adjustment value designated by the user and received in step S3 is −30% for color and −30% for black. Shows the case.

  Moreover, as shown in (2) of FIG. 7, the value of (R, G, B) of the pixel of interest as an example is (70, 70, 70), and as shown in (3) of FIG. The table selected as the reference table by the LUT selection unit 122a is the color conversion table 127 (2) (here, LUT2) having a maximum total ink ejection amount of 160%.

  In the third specific example, since the reduction of the density is instructed, the color conversion table 127 is not switched, and the color conversion processing by the reference table LUT2 is executed according to step S8, and (7) in FIG. As shown in FIG. 4, CMYK ink amount data is generated. The ink amount data of the target pixel is (C, M, Y, K) = (30%, 30%, 30%, 70%).

  Next, density adjustment (decrease) processing is performed for the color ink amount of the target pixel by the processing in step S9. Each ink amount data of (C, M, Y) = (30%, 30%, 30%) decreases by 30% according to the specified density adjustment value −30%, and (C ′, M ′, Y ') = (21%, 21%, 21%).

  Similarly, by the process of step S10, as shown in (9) of FIG. 7, the density adjustment (decrease) process is performed for the black ink amount of the target pixel. The ink amount of K = 70% is reduced by 30% according to the specified density adjustment value of −30%, and K ′ = 49%.

  In this way, the density adjustment process in the third specific example is executed. In the third specific example, since the density is decreased, the color conversion table 127 is not switched, and the density adjustment is performed on the ink amount data after the color conversion processing by the reference table.

  In the third specific example, if the density adjustment (decrease) is performed on the RGB values of the image data, (R, G, B) = (70, 70, 70) of the pixel of interest is The ink amount data obtained by adjusting to (R ′, G ′, B ′) = (100, 100, 100) and subsequent color conversion processing is (C, M, Y, K) = (35%, 35%). , 35%, 45%). On the other hand, when color adjustment is not performed (R, G, B) = (70, 70, 70) with the same table, (C, M, Y, K) = (30%, 30%, 30 %, 70%). The total ink ejection amount of both is 160% when the density adjustment is not performed, and 150% when the density adjustment is performed. Therefore, the ink amount does not decrease correspondingly even though the density reduction of -30% is instructed.

  In the third specific example, a case is considered where density adjustment (decrease) is performed after dot separation processing by the dot separation unit 124. FIG. 8 is a diagram illustrating the result of the dot separation process in the third specific example. (1) of FIG. 8 shows a case where the density reduction is performed after the dot separation process. The upper row shows dot generation amount data of the pixel of interest before density adjustment, and the lower row shows the result of density adjustment of −30% for the data.

  On the other hand, (2) of FIG. 8 shows dot generation amount data of the target pixel obtained as a result of step S11 after density adjustment is performed by the method of the present embodiment described above.

  Comparing the two, in the former ((1) in FIG. 8), medium dots are generated for a relatively low density of color (CMY), and large dots are generated for a density of black (K) which is not high. However, in the latter ((2) in FIG. 8), such medium dots and large dots are not observed. In the former case, a dot generation situation that is not preferable for image quality in terms of graininess or the like in the printing result is caused.

  Next, a modification of the above embodiment will be described. The apparatus configuration according to the modification is the same as that of the above-described embodiment shown in FIG. The difference from the above embodiment is that, even when the density adjustment is increased, the maximum value of the total ink ejection amount after density adjustment (the maximum value of the total color material amount) is within the maximum total ink ejection amount of the reference table. If there is, the color conversion table 127 is not switched in the high density direction. Hereinafter, differences from the above embodiment will be described.

  FIG. 9 is a flowchart illustrating the procedure of image processing in the modification. In steps S21 to S24 in FIG. 9, processing is performed in the same manner as steps S1 to S4 shown in FIG. Further, when the density adjustment designated by the user is not increased thereafter (No in step S25), the subsequent processing (steps S31 to S37) is the same as in FIG. 3 (No in step S5, S8 to S14). It is.

  If it is determined in step S25 that the density adjustment designated by the user is an increase (Yes in step S25), the color conversion unit 122 first determines whether the density adjustment specified by the user is an increase or not. The RGB color image data is converted into CMYK ink amount data by the reference color conversion table 127 (step S26).

  Thereafter, the color conversion unit 122 increases each ink amount of each pixel according to the density adjustment value received in step S23, and obtains the total ink amount of each pixel after the increase. For example, a pixel of (C, M, Y, K) = (30%, 30%, 30%, 30%) is 1.2 (120%) if the density adjustment value is + 20% for both color and black. ) To obtain (36%, 36%, 36%, 36%), and 144% is obtained as data of the total ink amount.

  Next, the color conversion unit 122 sets the data having the largest total ink amount among all the pixels as the maximum value of the total ink ejection amount after the density adjustment (step S27), and uses the value as the reference table. Is compared with the maximum total ink ejection amount (step S28).

  As a result, if the maximum value of the total ink ejection amount after density adjustment is larger and the ink ejection amount has exceeded (Yes in Step S28), the color conversion table 127 used by the LUT selection unit 122a is switched. It performs (step S29). In this switching, the color conversion table 127 having the maximum total ink ejection amount equal to or greater than the maximum value of the total ink ejection amount after the density adjustment is switched. Then, the color conversion unit 122 calculates the density reduction amount in the same manner as in step S7 described above (step S30).

  Thereafter (S31-S37) is processed in the same manner as in the case of FIG. 1 (S8-S14).

  On the other hand, if the actual maximum total ink ejection amount does not exceed the maximum total ink ejection amount of the reference table in step S28 (No in step S28), the density adjustment unit 123 performs color conversion in step S26. Color and black density increase processing is executed on the result, that is, on the color conversion result based on the reference table (steps S32 and S33). Specifically, for the ink amount data of the color conversion result, for each pixel, the CMY values are increased according to the color density adjustment value, and the K value is increased according to the black density adjustment value. Execute.

  Subsequent processing (S34-S37) is performed similarly to the case of FIG. 1 (S11-S14).

  FIG. 10 is a diagram illustrating data transition in the modified example. The example shown in FIG. 10 shows the case of the same conditions as the specific example shown in FIG. Accordingly, in this specific example, as shown in (1) of FIG. 10, the density adjustment value designated by the user and received in step S23 is + 50% for color and + 10% for black. Yes.

  Further, as shown in (2) of FIG. 10, the value of (R, G, B) of the pixel of interest as an example is (200, 150, 150), and as shown in (3) of FIG. The table selected as the reference table by the LUT selection unit 122a is the color conversion table 127 (1) (here, LUT1) having a maximum total ink ejection amount of 120%.

  In this specific example, since the density adjustment is an increase, the color conversion table 127 is switched to LUT3 in the case shown in FIG. 5, but here, the maximum value of the total ink ejection amount after the density adjustment is LUT1. As shown in (7) of FIG. 10, the reference table LUT1 is used as it is, and the color conversion process is executed by the process of step S26. As a result, (C, M, Y, K) = (0%, 30%, 30%, 20%) is obtained as the ink amount data of the focused pixel.

  Next, as shown in (8) of FIG. 10, the density adjustment (increase) process is performed for the color ink amount of the target pixel by the process of step S32. Each ink amount data of (C, M, Y) = (0%, 30%, 30%) increases by 50% according to the density adjustment value + 50%, and (C ′, M ′, Y ′) = ( 0%, 45%, 45%).

  Similarly, by the process of step S33, as shown in (9) of FIG. 10, the density adjustment (increase) process is performed for the black ink amount of the target pixel. The ink amount data of K = 20% increases by 10% according to the density adjustment value + 10%, and becomes K ′ = 22%.

  In this way, in this modification, even if the density adjustment is increased, the color conversion table 127 is not switched when the reference table can cover it, and the change in color condition due to table switching can be eliminated.

  As described above, the embodiment and the modifications thereof have been described. When the color conversion table 127 is switched when the density is increased, the user is notified that there is a possibility that the color may change from a desired hue. It may be. In this case, for example, the driver 12 executes processing for displaying the message on the display device of the host computer 1.

  Also, the color conversion table 127 may be switched during adjustment to reduce the density.

  As described above, in the image processing apparatus according to the present embodiment and the modification, the density adjustment value specified by the user is applied to the ink ejection amount data (ink amount data) used in the printer 2. Since the process is executed, the ink ejection amount changes in proportion to the value input by the user. Therefore, the user can control the amount of ink (coloring material amount) by adjusting the density, and the user needs such as prevention of bleeding and back-through, cost reduction by reducing the amount of ink, so-called filling is sufficient. Can be easily achieved.

  In addition, the density adjustment is performed separately for color and black, and the ink amount can be increased or decreased with different density adjustment values. Accordingly, it is possible to reduce the total ink ejection amount without degrading the quality of black characters, barcodes, and the like.

  In addition, since the density is increased within the range using the color conversion table in which the maximum total ink ejection amount is determined, the problem that the ink ejection amount is exceeded can be suppressed.

  Further, as in the above-described modification, even if the adjustment is to increase the density, if the total ink placement amount can be covered by the color conversion table that is the reference in the printing conditions, the table is used as it is, so the color tone Can be prevented from changing.

  In this embodiment, the image processing apparatus is for a line head ink jet printer, but the apparatus of the present invention can be applied to other types of printers.

  Further, the processing performed by the driver 12 in this embodiment can be executed by using the controller 13 on the printer 2 side, or may be executed by being divided into the host computer 1 and the printer 2. .

  The protection scope of the present invention is not limited to the above-described embodiment, but covers the invention described in the claims and equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 Host computer, 2 Printer, 11 Application, 12 Driver, 13 Controller, 14 Print execution part, 121 Rasterization part, 122 Color conversion part, 122a LUT selection part, 123 Density adjustment part, 124 Dot separation part, 125 Halftone processing part 126 print data conversion unit, 127 color conversion table, 128 dot separation table

Claims (8)

An image processing apparatus connectable to an image recording apparatus,
A color conversion unit that converts the image data expressed in the first color space into color material amount data expressed in the second color space of the color material used in the image recording apparatus;
A density adjustment unit that increases or decreases the color material amount data based on a designated adjustment value;
A dot separation unit for converting the color material amount data after the increase / decrease into dot generation amount data expressed by dot generation amounts according to dot sizes formed by the image recording device;
An image processing apparatus, comprising: a halftone processing unit that converts the dot generation amount data into data expressing the presence or absence of the dot formation. In claim 1,
The adjustment value is specified separately for chromatic color and black color,
The density adjustment unit increases or decreases the color material amount data of the chromatic color based on the adjustment value specified for the chromatic color, and the black color material amount data based on the adjustment value specified for the black color An image processing apparatus characterized by increasing or decreasing the value. In claim 1 or 2,
A table in which the image data and the color material amount data are associated with each other so that a total color material amount of the color material is within a limit value, and includes a plurality of color conversion tables having different limit values;
The image processing apparatus, wherein the color conversion unit selects the color conversion table based on the designated adjustment value, and performs the conversion using the selected color conversion table. In claim 3,
The color conversion unit selects the color conversion table having a larger limit value than the reference color conversion table when the designated adjustment value indicates an increase in density. . In claim 4,
The density adjustment unit selects a color conversion table having a large limit value, so that the color material amount data generated by the conversion processing by the color conversion unit exceeds the density increase indicated by the designated adjustment value. In the case of an increased value, an excess is reduced. In claim 3,
When the color conversion unit uses the reference color conversion table, the maximum value of the total color material amount of the color material amount data obtained after the processing by the density adjustment unit is the value of the reference color conversion table. If the limit value is not exceeded, the reference color conversion table is selected. A color conversion step of converting the image data expressed in the first color space into color material amount data expressed in the second color space of the color material used for printing;
A density adjustment step of increasing or decreasing the color material amount data based on a designated adjustment value;
A dot separation step of converting the color material amount data after the increase / decrease into dot generation amount data expressed by dot generation amount for each dot size formed on the print medium,
A halftone processing step of converting the dot generation amount data into data expressing the presence or absence of the dot formation. An image processing method comprising: A color conversion step of converting the image data expressed in the first color space into color material amount data expressed in the second color space of the color material used for printing;
A density adjustment step of increasing or decreasing the color material amount data based on a designated adjustment value;
A dot separation step of converting the color material amount data after the increase / decrease into dot generation amount data expressed by dot generation amount for each size of dots formed on the print medium;
An image processing program that causes an image processing apparatus to execute a halftone processing step of converting the dot generation amount data into data expressing the presence or absence of the dot formation.