CN1855997A - Image processing method, image processing apparatus, image forming apparatus, and recording medium - Google Patents

Image processing method, image processing apparatus, image forming apparatus, and recording medium Download PDF

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CN1855997A
CN1855997A CN 200610077045 CN200610077045A CN1855997A CN 1855997 A CN1855997 A CN 1855997A CN 200610077045 CN200610077045 CN 200610077045 CN 200610077045 A CN200610077045 A CN 200610077045A CN 1855997 A CN1855997 A CN 1855997A
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dither matrix
dithering process
cutting apart
definite result
pixel
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CN100452827C (en
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村上义则
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Sharp Corp
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Sharp Corp
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Abstract

In an image processing apparatus that performs a dither processing using a dither matrix based on the result of determination of the segmentation class to which the pixel to be processed belongs, to perform the dither processing, any of a plurality of pairs of threshold values is selected according to the result of determination of the segmentation class, and the selected pair of threshold values are compared with the value of the pixel to be processed, which are set so that in correspondence with each position of a dither matrix of a same configuration and a same size, a different dither processing is performed according to the result of determination of the segmentation class on part of the dither matrix and a same dither processing is performed irrespective of the result of determination of the segmentation class on the remainder of the dither matrix.

Description

Image processing method, image processing equipment, image forming apparatus and recording medium
Technical field
The present invention relates to a kind of image processing method, image processing equipment and image forming apparatus, its based on to the definite result of cutting apart classification under the pixel to be processed, utilize dither matrix (dither matrix) to carry out dithering process (dither processing), and the recording medium that relates to a kind of logger computer program, be used to make computer based in to the definite result of cutting apart classification under the pixel to be processed, utilize dither matrix to carry out dithering process.
Background technology
In recent years, because the digitlization of OA equipment promptly advances and the demand of coloured image output is constantly increased, be widely used such as the output equipment of electrofax digital color copier and ink-jet and thermal transfer printer.For example, use these output equipments can export from image information of importing such as the input equipment of digital camera and image reading apparatus and the image information of creating on computers.In these output equipments, often to carry out pseudo-tone reproduction processes (pseudo tone reproduction processing) to the image information of input.
A kind of pseudo-tone reproducing method is multistage (multi-level) dither method.For example, for the pixel of as shown in Figure 1 dither matrix (here, the order that the output valve that digitized representation in the grid is higher is assigned with), based on pixel value and a plurality of corresponding threshold are relatively carried out quantification, and export among a plurality of output valves, perhaps export output valve based on translation table.
A kind of like this technology has been proposed, that is: the dither matrix that has a concentrated type of k (k 〉=2) individual cores (core) by use forms screen angle (screen angle), and make that density in dither matrix (density) is not that the frequency of occurrences of the point (dot) of highest (level) is not more than k, can obtain the improvement of reproducibility and such as the stability of the picture quality of level and smooth tone performance (representation); And the density that increases in the dither matrix by (uniformly) equably makes the difference of the density level between the invocation point be not more than 1, thus, resolution can be maintained in the permissible scope, and half tone dot (halftone dot) is represented well-balancedly, thereby prevented screen angle disappearance (referring to, for example, Japanese Patent Application Publication file No.61-189774 (1986)).
For handling the pixel that is confirmed as fringe region by cutting apart (segmentation), in order clearly to reproduce character and fine rule, different with multistage dithering process for other zone except that the zone, edge, for example, be applied to all pixels by using 1 * 1 dither matrix that identical tint correction is handled, perhaps will make the difference of the density level between the invocation point be not more than 1 multistage dithering process and be applied to identical input value.
Make ripple be difficult to appear at the technology in the half-tone regions as in multistage dithering process, reproducing simultaneously than low-density, a kind of like this technology has been proposed, promptly, in the low-density part, output valve is distributed to pixel with predesigned order in dither matrix, so that increase partly, and in the high density part, output valve is distributed to pixel singly with predesigned order in dither matrix, so that increase (for example, Japanese Patent Application Publication file No.2001-257893) equably.
Summary of the invention
Show processing when all pixels being carried out multistage shake, in the dither matrix that comprises four submatrixs as shown in Figure 1, from the low-density to the high density, produce output (the digitized representation output valve in the grid, as shown in Figure 2 here; Upper left side density is low, lower right density height) time, shown in the concept map of dither matrix screen angle as shown in Figure 3, owing to formed screen angle (dotted line among Fig. 3), and distance between points is not short, has therefore caused the sawtooth (jaggy) of character and fine rule part.In the technology of Japanese Patent Application Publication file No.61-189774 (1986), also can partly cause sawtooth at character and fine rule.
When utilizing dither matrix (, the digitized representation in the grid distributes the order of higher output valve) as shown in Figure 4 to carry out multistage dithering process here, (here, the numeral in the grid is an output valve with generation output as shown in Figure 5 from the low-density to the high density; Upper left side density is low, lower right density height) time, though because screen angle is that 0 degree and point are shorter with the distance of putting, thereby make and compare sawtooth than difficult identification with the dither matrix of Fig. 1, but output valve is with a behavior cyclomorphosis, so that only delegation dark (dark) or triplex row are dark, thereby the fineness degree (thickness) of the fine rule that (horizontal direction in the accompanying drawing) extends on main scanning direction shows difference according to reading the position.
Even in the multistage dithering process of the pixel that is defined as the zone except that the zone, edge by dividing processing being used as shown in Figure 2, all pixels that are confirmed as fringe region are used identical tint correction to be handled, when perhaps making the difference of the density level between the invocation point be not more than 1 multistage dithering process to identical output valve application, because the reproduction density in edge region and the zone except that the zone, edge is difficult to (coinside) consistent with each other, and have difference between reproduction resolution edge region and the zone except that the zone, edge, the switching of processing also can be discovered.Even by using as shown in Figure 4 dither matrix not very poor and when reproducing resolution relatively well fringe region being carried out as shown in Figure 5 multistage dithering process to the tone reproducibility, owing to reproduce the resolution difference, can be easily consistent with each other although reproduce density, the switching of processing also can be perceived.
When the technology of Japanese patent application open file No.2001-257893 is applied to all pixels, though can export the image that has suppressed to be partly with sawtooth at character and fine rule, pixel has but more been exported unsettled point, so that can perceive more inhomogeneities in the image of output.
Consider that such situation made the present invention, and its objective is provides a kind of image processing method, it can utilize the dither matrix of identical configuration and same size, according to definite result of cutting apart classification is carried out different dithering process to the part of dither matrix, suppress thus owing to switching the graphical quality decline that dithering process causes.
Another object of the present invention provides a kind of image processing method, it can be according to any dither matrix in a plurality of dither matrixs of the combination of the dither matrix of the identical configuration of definite result of cutting apart classification being selected comprise varying number and same size, and be used to store the necessary memory span of a plurality of threshold values to (pair) according to definite result of cutting apart classification being carried out different dithering process to the part of the dither matrix that is included in configuration in the selected dither matrix, identical and same size, reducing with this.
Another object of the present invention provides a kind of image processing method, a kind of image processing equipment, a kind of image forming apparatus, a kind of computer program and a kind of recording medium, it can carry out only dithering process according to the zone, and can suppress as follows owing to threshold value is switched the image quality decline that causes, described step is: in order to carry out dithering process, according to selecting any threshold of a plurality of threshold value centerings right to definite result of cutting apart classification, and selected threshold value pair and value with processed pixel compared, wherein, described threshold value is to being configured such that each position corresponding to the dither matrix of identical configuration and same size, carry out different dithering process according to definite result of cutting apart classification being come a part to dither matrix, and no matter to definite result of cutting apart classification how, all the remainder of dither matrix is carried out identical dithering process.。
Another object of the present invention provides a kind of image processing method, whether it can according to being that fringe region selects threshold value right to definite result of cutting apart classification, comes thus in fringe region and the zone except that the zone, edge each is carried out only dithering process.
Another object of the present invention provides a kind of image processing method, it can be according to the value of the pixel that will handle, no matter how to definite result of cutting apart classification, all with same position as starting point, increase is as the dithering process result's of each position of the dither matrix of identical configuration and same size pixel value, and the image quality that suppresses thus to cause owing to the right switching of a plurality of threshold values descends.Another object of the present invention provides a kind of image processing method, it can be when being fringe region to definite result of cutting apart classification, value according to the pixel that will handle, the pixel value of the starting point of the dither matrix of identical configuration and same size is increased to predetermined value, pixel value with other position is increased to predetermined value equably then, and sawtooth appears in the fringe region that is suppressed at thus such as character.
Another object of the present invention provides a kind of image processing method, it can form one group and to definite result of cutting apart classification during for fringe region at the dither matrix of a plurality of identical configurations and same size, value according to the pixel that will handle, the pixel value of the predetermined starting point of the starting point of described dither matrix is increased to predetermined value, then other starting point of dither matrix and the pixel value of other position are increased to predetermined value equably, sawtooth and acnode appear in the fringe region that comes thus better to be suppressed at such as character.
Another object of the present invention provides a kind of image processing method, it can come suppressing owing in the image quality decrease that the right switching of a plurality of threshold values causes, suppress the position inhomogeneities of the tone characteristic of fringe region and come by arranging predetermined starting point equably.
Another object of the present invention provides a kind of image processing method, it is when being not fringe region to definite result of cutting apart classification, according to value with processed pixel, the pixel value of the starting point of the dither matrix of identical configuration and same size is increased predetermined value, the pixel value of other position is increased to predetermined value with putting by turn then, improves the gray scale (gradation) in the zone except that the zone, edge thus.
No matter to definite result of cutting apart classification how another object of the present invention provides a kind of image processing method, and it is based on the total tint correction information and executing tint correction of pixel, and, improve the processing speed that tint correction information produces thus.
Another object of the present invention provides a kind of image processing method, a kind of image processing equipment, a kind of image forming apparatus, a kind of computer program and a kind of recording medium, its basis is to cutting apart definite result of classification, select any data in a plurality of data, and carry out dithering process based on selected data, it can carry out dithering process with two-forty thus, wherein, described a plurality of data representation (representativeof) utilizes every pair of the right dithering process of a plurality of threshold values relation of handling between preceding pixel value and the processing back pixel value, and described selected data also are to represent described relation.
According to of the present invention, based on the definite result of cutting apart classification under the pixel to be processed is carried out in the image processing method of the dithering process of utilizing dither matrix, have the right identical configuration of a plurality of threshold values and the dither matrix of same size by use, according to cutting apart definite result of classification, the part of dither matrix is carried out different dithering process.Thereby, can carry out the only dithering process in this zone this part.And, because according to not being to all but a part is carried out different dithering process to definite result of cutting apart classification, and not according to definite result of cutting apart classification being come remainder carry out different dithering process to dither matrix, so the switching of dither matrix is difficult for discovering, thereby can suppress the image quality decrease that the switching owing to dithering process causes.
According to of the present invention, carry out in the image processing method of the dithering process of utilizing dither matrix based on definite result the zone under the pixel to be processed, according to cutting apart definite result of classification, selection comprises any dither matrix of a plurality of dither matrixs of combination of the dither matrix (hereinafter referred to as submatrix) of the varying number of identical configuration and same size, and according to definite result of cutting apart classification is carried out different dithering process to the part of the dither matrix that is included in identical configuration in the selected dither matrix and same size.Thereby the quantity of submatrix that can be by reducing combination reduce and is used to store a plurality of threshold values to necessary memory span.In the zone that does not take the bulk continuum, even the reproducibility of tone is poor slightly, its influence to output image quality is also relatively very little.Therefore, at the dither matrix that is used for such zone is carried out dithering process, the minimizing of submatrix quantity can not go wrong yet.In the continuous tone zone,, therefore increased the quantity of the submatrix of combination owing to more emphasis is placed upon on the tone characteristic.
In image processing method according to the present invention, in order to carry out dithering process, according to selecting any threshold value of a plurality of threshold value centerings right to definite result of cutting apart classification, and the selected threshold value pair value with pixel to be processed is compared, described threshold value is to being configured such that each position corresponding to the dither matrix of identical configuration and same size, according to definite result of cutting apart classification is carried out different dithering process to the part of dither matrix, and no matter how definite result of cutting apart classification is carried out identical dithering process to the remainder of dither matrix.Thereby, in the part of dither matrix, can carry out only dithering process corresponding to this zone, and in the remainder of dither matrix, carry out total dithering process by consideration of regional not, can suppress because threshold value is switched the image quality decrease that causes.Here, above-mentioned dithering process not only can form the image forming apparatus of image by image processing equipment or on paper and carry out, and also can be carried out by computer.When above-mentioned processing is carried out by computer, for example offer computer by program being recorded the computer program that to carry out above-mentioned processing on the recording medium.
In image processing method according to the present invention, according to whether being that fringe region selects described threshold value right to definite result of cutting apart classification.Thereby, for carrying out suitable dithering process as the fringe region of character and as in the zone except that the zone, edge in half-tone regions and continuous tone zone each.
In image processing method according to the present invention, according to pixel value to be processed, no matter how to definite result of cutting apart classification, all with identical position, the position with other threshold value as starting point, increase as pixel value the dithering process result of each position of dither matrix with the right identical configuration of threshold value and same size.Thereby, owing to not considering that the definite result to cutting apart classification forms fixing screen angle, and no matter to definite result of cutting apart classification how the output valve of starting point all be similar value, therefore because the switching of the dithering process that the threshold value switching causes is inconspicuous, thereby can suppress the image quality decrease that causes owing to the right switching of a plurality of threshold values.
In image processing method according to the present invention, when definite result of cutting apart classification is fringe region, according to pixel value to be processed, the pixel value of the starting point of the dither matrix of identical configuration and same size is increased to predetermined value, and the pixel value with other position of dither matrix is increased to predetermined value equably then.Thereby sawtooth appears in the fringe region that can be suppressed at such as character.
In image processing method according to the present invention, when a plurality of dither matrixs of identical configuration and same size constitute one group, and when definite result of cutting apart classification is fringe region, according to pixel value to be processed, the pixel value of the predetermined starting point of the starting point of dither matrix is increased to predetermined value, then other starting point of dither matrix and the pixel value of other position is increased to predetermined value equably.Thereby,, also can be suppressed at better in the fringe region such as character and sawtooth and acnode occur although the gray scale of fringe region is low slightly.
In image processing method according to the present invention, described predetermined starting point is distributed equably.Thereby, when the image quality that can suppress to cause owing to the right switching of a plurality of threshold values descends, can also suppress the position inhomogeneities of the tone characteristic of fringe region.
In image processing method according to the present invention, when definite result of cutting apart classification is not fringe region, according to pixel value to be processed, the pixel value of the starting point of the dither matrix of identical configuration and same size is increased to predetermined value, and ground, position is increased to predetermined value with the pixel value of other position of dither matrix one by one then.Thereby, improved gray scale such as the zone except that the zone, edge in half-tone regions or continuous tone zone.
According to image processing method of the present invention, based on the total tint correction information and executing tint correction of pixel, and no matter to definite result of cutting apart classification how.Thereby and for each all prepares tint correction information and switch to compare to definite result of cutting apart classification, the speed that produces the tint correction information processing is improved, and can reduce the memory span that is used to store tint correction information.And total tint correction information carries out because tint correction is based on, so the switching of dithering process is inconspicuous.
In image processing method according to the present invention, in order to carry out dithering process, according to the arbitrary data in a plurality of data that definite option table as a result of cutting apart classification are shown in pixel value before the dithering process and the relation between the pixel value after the dithering process, and value according to the data transaction pixel to be processed of the described contact of selected expression, wherein, described data are set so that according to definite result of cutting apart classification is carried out different dithering process to the part of the dither matrix of identical configuration and same size, and no matter how definite result of cutting apart classification are carried out identical dithering process to the remainder of dither matrix.In the present invention, in order to carry out dithering process, be illustrated in the pixel value before the every pair of processing that utilizes the right dithering process of a plurality of threshold values and handle after pixel value between the data of relation be stored in advance in the storage area, according to any data in the data of definite result of cutting apart classification being selected represent described relation, and, thereby no longer need to carry out comparison with threshold value based on the data transaction pixel value to be processed of the described relation of selected expression.Therefore, can carry out dithering process at a high speed.Here, above-mentioned dithering process not only can form the image forming apparatus of image by image processing equipment or on paper and carry out, and also can be carried out by computer.When this is handled when being carried out by computer, for example offer computer by the computer program that computer program recorded will be carried out this processing to the recording medium.
According to of the present invention, based on the definite result of cutting apart classification under the pixel to be processed being utilized dither matrix carry out in the image processing equipment of dithering process, provide following parts: storage area, it is right that it stores a plurality of threshold values, these threshold values are to being configured such that each position corresponding to the dither matrix of identical configuration and same size, according to definite result of cutting apart classification is carried out different dithering process to the part of dither matrix, and no matter how definite result of cutting apart classification is carried out identical dithering process to the remainder of dither matrix; And selection part, it is right according to any threshold value that definite result's selection of cutting apart classification is stored in the described threshold value centering in the described storage area, wherein, in order to carry out dithering process, will pair compare by the threshold value of described selection portion component selections with pixel value to be processed.
According to of the present invention, carry out in the image processing facility of dithering process based on the definite result of cutting apart classification under the pixel to be processed being utilized dither matrix, provide following parts: storage area, the pixel value of its storage representation before dithering process and a plurality of data of the relation between the pixel value after the dithering process, these data are configured such that according to definite result of cutting apart classification is carried out different dithering process to the part of the dither matrix of identical configuration and same size, and no matter how definite result of cutting apart classification is carried out identical dithering process to the remainder of dither matrix; And selection part, it is according to the arbitrary data in the data of definite result of cutting apart classification being selected the described relation of expression in the described storage area that is stored in, wherein, in order to carry out dithering process, based on value by the data transaction pixel to be processed of the described relation of expression of described selection portion component selections.
Image forming apparatus according to the present invention is provided with the image processing equipment of the invention described above, and forms the image processing system by the image of image processing device processes on paper.
In recording medium according to the present invention, write down computer program to be used for based on the definite result of cutting apart classification under the pixel to be processed being utilized dither matrix carry out dithering process, described computer program comprises step: make computer according to selecting any threshold value of a plurality of threshold value centerings right to definite result of cutting apart classification, these threshold values are to being configured such that each position corresponding to the dither matrix of identical configuration and same size, according to definite result of cutting apart classification is carried out different dithering process to the part of dither matrix, and no matter how definite result of cutting apart classification is carried out identical dithering process to the remainder of dither matrix; And make described computer that the selected threshold value pair value with pixel to be processed is compared, so that carry out dithering process.
In recording medium according to the present invention, write down computer program to be used for based on the definite result of cutting apart classification under the pixel to be processed being utilized dither matrix carry out dithering process, described computer program comprises step: make computer according to the arbitrary data in a plurality of data that definite option table as a result of cutting apart classification are shown in pixel value before the dithering process and the relation between the pixel value after the dithering process, these data are configured such that according to definite result of cutting apart classification is carried out different dithering process to the part of the dither matrix of identical configuration and same size, and no matter how definite result of cutting apart classification is carried out identical dithering process to the remainder of dither matrix; And make described computer based in the value of the data transaction pixel to be processed of the described relation of selected expression, to carry out dithering process.
By below in conjunction with accompanying drawing in detail, describing above and other objects of the present invention and feature will be clearer.
Description of drawings
Fig. 1 is the view of example that expression is used for the dither matrix of multistage dithering process;
Fig. 2 is the view that is illustrated in the example from low-density to highdensity output valve when using dither matrix shown in Figure 1;
Fig. 3 is the conceptual view of screen angle;
Fig. 4 is the view of the example of the traditional dither matrix of expression;
Fig. 5 is the view that is illustrated in the example from low-density to highdensity output valve when using shown in Figure 4 traditional dither matrix;
Fig. 6 is the block diagram that expression has the schematic construction of the digital color copier (image forming apparatus) according to image processing equipment of the present invention;
Fig. 7 is the block diagram of example of structure of the relevant portion of expression tone rendering processing section;
Fig. 8 is the table that is illustrated in the example of the contact between input density value (pixel density value), threshold value and the output valve;
Fig. 9 is the view that is illustrated in the example from low-density to highdensity output valve when using dither matrix shown in Figure 1;
Figure 10 is the view of another example of expression from low-density to highdensity output valve;
Figure 11 is the view that is illustrated in the example of the relation between input value in the dither matrix and the total output valve;
Figure 12 is the view of another example that expression is used for the dither matrix of multistage dithering process;
Figure 13 is the view that is illustrated in the example from low-density to highdensity output valve when using dither matrix shown in Figure 12;
Figure 14 is that expression comprises the block diagram according to the example of structure of the image formation system of image processing equipment of the present invention;
Figure 15 is the block diagram of the example of expression computer configuation;
Figure 16 is the flow chart of the example of expression dithering process program;
Figure 17 is the block diagram of another example of structure of the relevant portion of expression tone rendering processing section;
Figure 18 is the block diagram of the example of expression computer configuation;
Figure 19 is the flow chart of another example of expression dithering process program;
Figure 20 is the view of another example of expression from low-density to highdensity output valve;
Figure 21 is the view of another example of expression from low-density to highdensity output valve;
Figure 22 is a view of explaining the method for selecting wherein the submatrix that the output valve as the numbering of core at first increased from a plurality of submatrixs;
Figure 23 is another example of the submatrix that the output valve as the numbering of core at first increased is selected wherein in expression from a plurality of submatrixs a view; And
Figure 24 is the view of another example of expression from low-density to highdensity output valve.
Embodiment
Accompanying drawing below with reference to the expression embodiment of the invention specifically describes the present invention.
(first embodiment)
Fig. 6 is that expression has the block diagram according to the schematic construction of the digital color copier (image forming apparatus) 30 of image processing equipment 10 of the present invention.Digital color copier 30 has image input device 32, image processing equipment 10, image output device (image forming apparatus) 34 and guidance panel 36.Image processing equipment 10 has A/D (modulus) conversion portion 11, shade (shading) correction portion 12, input tint correction part 13, dividing processing part 14, colour correction part 15, black generates and background color (under color) is removed part 16, space filtering processing section 17, output tint correction part 18 and tone rendering processing section 19.
Image input device 32 comprises, for example, have the image reading apparatus of CCD (charge coupled device), it is read from the light image (light image) of the paper reflection of record original image by CCD, as analog rgb (red, green, blue) signal, and they are outputed to image processing equipment 10.The analog rgb signal that is read by image input device 32 is transferred to image processing equipment 10 by the order with A/D conversion portion 11, shadow correction part 12, input tint correction part 13, dividing processing part 14, colour correction part 15, black generation and undercolour removal part 16, space filtering processing section 17, output tint correction part 18 and tone rendering processing section 19, and in the end, digital CMYK (blue or green, pinkish red, yellow, black) signal is output to image output device 34.
A/D conversion portion 11 is the digital rgb signal with the analog rgb conversion of signals of input.12 pairs of digital rgb signals (hereinafter referred to as rgb signal) that come from 11 transmission of A/D conversion portion of shadow correction part are carried out and are handled, to remove the various distortions that produce in illuminator, image formation system and the image capture system of image input device 32.Input tint correction part 13 is adjusted the color balance of having been removed the rgb signal (RGB reflected signal) of various distortions by shadow correction part 12, and rgb signal is converted to signal such as density signal, such signal is handled by the image processing system that image processing equipment 10 is adopted easily.
Dividing processing part 14 is zone such as character zone (fringe region), half-tone regions and picture zone (picture area) based on the rgb signal of input with the pixel segmentation in the input picture.Dividing processing part 14 outputs to colour correction part 15, black generation and undercolour removal part 16, space filtering processing section 17, output tint correction part 18 and tone rendering processing section 19 with classification (segmentation classes) signal (to cutting apart definite result of classification) of cutting apart of represent pixel affiliated area, and will output to colour correction part 15 subsequently from the rgb signal former state of input tint correction part 13 inputs.
When carrying out dividing processing, for example, calculating is comprising that the n of current pixel to be processed * the m piece (for example, the density contrast of the maximum 15 * 15) and the numerous and diverse degree of summation density (sum total density busyness), and compare with a plurality of predetermined thresholds, be page layout background zone, (continuous tone zone, printing paper (picture) zone thus with pixel segmentation; The also corresponding described continuous tone of image zone by hot transfer printing and the printer output of sublimating and dyeing type), character zone (fringe region) or half-tone regions (for example referring to Japanese Patent Application Publication file No.2002-232708), wherein said maximal density difference is exactly poor between least density value (minimum pixel value) and high intensity values (maximum pixel value), and the numerous and diverse degree of described summation density is the summation of the absolute value of the density contrast (pixel value poor) between the neighbor.
In the density distribution in page layout background zone, usually because the density change is very little, so maximal density difference and the numerous and diverse degree of summation density are all very little.In the density distribution in printing paper zone because density changes smoothly, so maximal density difference and the numerous and diverse degree of summation density are all very little, but big slightly than in the page layout background zone.In the density distribution of half-tone regions, the maximal density difference changes among half tone dot, and density changes along with the variation of the half tone dot quantity in the numerous and diverse degree of summation density, so the numerous and diverse degree of summation density is very high with the ratio of maximal density difference.Therefore, when the numerous and diverse degree of summation density was higher than maximal density difference and character/halftoning and determines the product of threshold value (one of above-mentioned threshold value), current pixel was confirmed as half-tone regions.In the density distribution of character zone, though the maximal density difference is very big, and therefore the numerous and diverse degree of summation density is very high, and owing to density changes less than half-tone regions, so the numerous and diverse degree of summation density is lower than half-tone regions.Therefore, when the numerous and diverse degree of summation density was lower than maximal density difference and character/halftoning and determines the product of threshold value, current pixel was confirmed as character zone (fringe region).
Therefore, at first, carry out to the maximal density difference calculated and the comparison between the maximal density difference limen value and to the numerous and diverse degree of summation density that calculated and the comparison between the numerous and diverse degree threshold value of summation density.When the maximal density difference is lower than the numerous and diverse degree threshold value of density less than maximal density difference limen value and the numerous and diverse degree of summation density, current pixel is confirmed as page layout background/printing paper zone, and under other situation except this situation, current pixel is confirmed as character/half-tone regions.When current pixel is confirmed as page layout background/printing paper zone, carries out the maximal density difference calculated and page layout background/printing paper are determined comparison between the threshold value.In the maximal density difference hour, current pixel is confirmed as the page layout background zone, and when the maximal density difference was big, current pixel was confirmed as the printing paper zone.When current pixel is confirmed as character/half-tone regions, carries out the numerous and diverse degree of summation density that calculated and multiply by character/halftoning and determine comparison between the maximal density difference of threshold value.When summation density was low numerous and diversely, current pixel was confirmed as character zone (fringe region), and when the numerous and diverse degree of summation density was higher, current pixel was confirmed as half-tone regions.
For reproducing colors verily, colour correction part 15 is carried out the processing of removing look turbid (color muddiness) based on the spectral characteristic of the cmy color material that contains unwanted absorption composition.The example of this processing method comprises a kind of preparation in the rgb signal of input and the contact between the CMY signal of the output method as LUT (look-up table), and a kind of (colormasking) method of utilizing the color of following transformation matrix to shelter:
C M Y = a 11 a 12 a 13 a 21 a 22 a 23 a 31 a 32 a 33 R G B
When using the color masking method, with the L of the color of when given CNY data are provided for image output device 34, exporting *a *b *Value (CIE1796L *a *b *(CIE represents CommissionInternational de l ' Eclairage, L to signal *Expression brightness, a *Expression redness-green, and b *Expression yellow-blueness)) identical L *a *b *The colour code of value (color patch) when being read by image input device 32 the RGB data and the cmy data that is provided for image output device 34 by with many compositions to providing (amultiplicity of pairs), and calculate from a from their combination 11To a 33The transformation matrix coefficient.Utilize these coefficients to carry out colour correction.In order to strengthen accuracy, can add secondary or high-order term more.
Black generates and undercolour removal part 16 is carried out the black generation so that generate black (K) signal from the CMY tristimulus signal, and convert the CMY tristimulus signal to CMYK four chrominance signals, wherein, described CMY tristimulus signal has passed through colour correction and has produced new CMY Signal Processing by the part that deducts original CMY signal overlap.Handle from the image of the CMYK signal of black generation and 16 inputs of undercolour removal part space filtering processing section 17, thereby so that by utilizing digital filter execution space filtering to handle the correction space frequency characteristic to prevent that smudgy (blur) of output image and granularity from reducing (granularity degradation) based on cutting apart sorting signal.Output tint correction part 18 carries out that the output tint corrections are handled so that density signal etc. is converted to the half-tone regions ratio, and described half-tone regions is than the characteristic value that is image output device 34.Tone rendering processing section 19 is carried out tone rendering to the image of CMYK signal and is handled based on cutting apart sorting signal, so that the final tone of (pseudly) reproduced image virtually.
For example, be defined as by dividing processing part 14 in the zone of character zone (fringe region), in order to increase the reproducibility of black character particularly or color character, acutance (sharpness) enhancement process during handle by space filtering space filtering processing section 17 strengthens radio-frequency component.Simultaneously, 19 pairs of tone rendering processing sections are suitable for reproducing the high-resolution screen execution binaryzation (binarizing) or the multistep treatment of radio-frequency component.Be defined as by dividing processing part 14 on the zone of half-tone regions, carry out the halftoning composition of low-pass filtering treatment by space filtering processing section 17, and focus on the screen execution binaryzation or the multistep treatment of gray scale by 19 pairs of tone rendering processing sections with the removal input.In the zone that is defined as the printing paper zone by dividing processing part 14, the screen that is focused on the tone reproducibility by 19 pairs of tone rendering processing sections is carried out binaryzation or many-valuedization processing.
In the present invention, 19 bases described after a while segmentation result in tone rendering processing section is carried out different multistage dithering process.Here, different dithering process are meant the dithering process of using different threshold values.Though view data comprises the density value of the color of CMYK, but because no matter how the colour component of view data all carries out similar multistage dithering process, therefore in the following description, only explain processing, and will be omitted the explanation of the processing of other colour component for a kind of density value (pixel value) of colour component.
The view data through above-mentioned processing is temporarily stored in the unshowned storage device, and is read out in predetermined timing, outputs to image output device 34 then.Image output device 34 outputs to recording medium (for example, paper) based on view data with coloured image.Although can enumerate use xerography or ink-jet method the coloured image output equipment as an example, image output device 34 is not limited thereto.Above-mentioned processing is controlled by unshowned CPU (CPU).Guidance panel 36 comprises that for example, touch panel wherein is together with each other such as the display part of LCD with such as the operation part that button is set.The operation of image input device 32, image processing equipment 10 and image output device 34 is controlled according to the information of importing from guidance panel 36 by CPU.
Fig. 7 is the block diagram of example of structure of the relevant portion of expression tone rendering processing section 19.Tone rendering processing section 19 has threshold process part 42, threshold value is selected part (selector) 44 and threshold value output storage area (memory) 46.Threshold value output storage area 46 is each location of pixels 15 threshold values of storage and 16 output valves that are used for the dither matrix of dithering process.Here, for such as each storage threshold and output valve in the segmentation result in fringe region (for example, character zone) and other zone except that the zone, edge (for example, half-tone regions, printing paper zone, page layout background zone).Cut apart sorting signal and be imported into threshold value selection part 44, and it is that fringe region is selected threshold value and output valve that threshold value selects part 44 to cut apart sorting signal based on this, perhaps select threshold value and output valve for the zone except that the zone, edge, read them from threshold value output storage area 46, and threshold value and the output valve that reads is transferred to threshold value selection part 44.Though in the present embodiment, be used for the threshold value in the zone except that the zone, edge and the pixel that output valve is used to belong to half-tone regions, but also can prepare to be used for the threshold value and the output valve of half-tone regions individually, so that under the situation of half-tone regions, select and use them.
The pixel of 42 pairs of input image datas of threshold process part according to according to cut apart sorting signal select the order of threshold value carry out with the position that has been assigned with the high output valve (pixel value) in the dither matrix corresponding a plurality of (for example, 15) comparison of threshold value, and export in a plurality of (for example, 16) output valve one based on the result of described comparison.In the present embodiment, 0 to 255 input image data (input density value) is carried out multistage dithering process to export the output image data (output valve) of 16 grades (0 to 15).
Figure 8 illustrates the example of the contact between input density value (pixel density value), threshold value and output valve.
As shown in Figure 8, according to be in the dither matrix each position i (i=0,1,2 ..., n) a plurality of threshold value Th[i of Zhun Beiing] [j] (j=0,1,2 ..., 14; Here, Th[i] [j]≤Th[i] [j+1]), and which higher (result relatively) exports a plurality of output valve Out[j among the input density value x] (j=0,1,2 ..., 15; Here, Out[j]≤Out[j+1]) in one.Here, threshold value is set, so that in the part of dither matrix, according to definite result of cutting apart classification is carried out different dithering process, and in the remainder of dither matrix, no matter how definite result of cutting apart classification is carried out identical dithering process.
Fig. 1 is the view of example that expression is used for the dither matrix of multistage dithering process.Fig. 2 and Fig. 9 are the views of representing the example from low-density to highdensity output valve respectively.The dither matrix of Fig. 1 comprises a plurality of submatrixs (among the figure being four), the order that on behalf of the output valve of Geng Gao, the numeral in the grid (hereinafter referred to as numbering) be assigned with.Digitized representation output valve in Fig. 2 and 9 the grid.
Under the situation of as shown in Figure 1 dither matrix, the multistage dithering process that is used for the zone except that the zone, edge is such, for example, and by the relation between the following threshold value:
Th[i][j]≤Th[i+1][j]
Th[4k+3][j]≤Th[4k][j+1]
Th[4k+3][14]≤Th[4k+4][0]
(k＝0，1，2，…，8)，
As shown in Figure 2, so that in each submatrix, be increased to 15 from 1 according to the order of numbering, the output valve of each numbering from low-density (upper left side of Fig. 2) to high density (lower right of Fig. 2).For example, be increased to after 15 from 1 in output valve as the numbering " 0 " of the core (starting point) of submatrix, " 1 ", " 2 " and " 3 ", the output valve of numbering " 4 ", " 5 ", " 6 " and " 7 " is increased to 15 from 1, then, by similar mode, the output valve of the numbering of a position in each submatrix is increased to 15 from 1.
Under the situation of as shown in Figure 1 dither matrix, the multistage dithering process that is used for fringe region is such, comes by the relation between the following ground threshold value:
Th[i][j]≤Th[i+1][j]
Th[3][j]≤Th[0][j+1]
Th[3][14]≤Th[4][0]
Th[39][j]≤Th[4][j+1]，
As shown in Figure 9, in each submatrix from low-density (upper left side of Fig. 9) to high density (lower right of Fig. 9), be increased to 15 as the output valve of the numbering " 0 " of core, " 1 ", " 2 " and " 3 " from 1, and the output valve of other numbering is increased equably with the order of numbering.For example, be increased to after 15 from 1 in output valve as the numbering " 0 " of core (starting point), " 1 ", " 2 " and " 3 ", the output valve of numbering " 4 " to " 39 " is increased to 1 with its numeral order, then, the output valve of numbering " 4 " to " 39 " by similar mode is increased to 15 from 2 equably with its numeral order.
In the present invention, numbering " 0 ", " 1 ", " 2 " and " 3 " for fringe region as the core of dither matrix, and be positioned at identical position for numbering " 0 ", " 1 ", " 2 " as the core of dither matrix in the zone except that the zone, edge with " 3 " in dither matrix, and its output valve increases in a similar fashion.Therefore, even when fringe region is carried out different multistage dithering process with the zone except that the zone, edge, also can prevent the change (shifting) of screen angle.
Shown in Fig. 2 and 9, to compare with the multistage dithering process that the zone except that the zone, edge is carried out, edge region is carried out the bigger multistage dithering process of inhomogeneities; But because fringe region is not continuous on the scope of a broad, so the influence of inhomogeneities is very little.In multistage dithering process to fringe region, because four pixels in 40 pixels of dither matrix, be that a pixel (as numbering " 0 ", " 1 ", " 2 " and " 3 " of core) in ten pixels of each submatrix is converted into and the identical output valve of multistage dithering process that is used for the zone except that the zone, edge, therefore the switching of multistage dithering process is inconspicuous.In addition, because the output valve of nine pixels in ten pixels of each submatrix equates with each input density value basically, therefore partly can export the image that has fabulous reproducibility and suppressed sawtooth for character part and fine rule.
Though in the present embodiment, output valve Out[j] (j=0,1,2 ..., 15; Here, Out[j]≤Out[j+1]) be from 0 to 15 4 bit integer, but they also can be based on 16 integer values that the characteristic of image output device 34 is selected from 0 to 255 8 bit integer.
For the multistage dithering process of fringe region, can use diverse ways.Figure 10 is the view of another example of expression from low-density to highdensity output valve.Under the situation of as shown in Figure 1 dither matrix, by the relation between the following threshold value:
Th[i][j]≤Th[i+1][j]
Th[3][j1]≤Th[0][j1+1]
Th[3][12]≤Th[4][0]
Th[39][j1]≤Th[4][j1+1]
Th[39][j2]≤Th[0][j2+1]
(j1=0,1,2 ..., 11, perhaps j2=12,13),
As shown in figure 10, for each submatrix from low-density (upper left side of Figure 10) to high density (lower right of Figure 10), output valve as the numbering " 0 " of core, " 1 ", " 2 " and " 3 " is increased to 13 from 1, and the output valve of other numbering is increased to 13 equably with numeral order, all is increased to 15 equably then.For example, be increased to after 13 from 1 in output valve as the numbering " 0 " of the core (starting point) of submatrix, " 1 ", " 2 " and " 3 ", the output valve of numbering " 4 " to " 39 " is increased to 1 with numeral order, then in a similar fashion, the output valve of numbering " 4 " to " 39 " is increased to 13 from 2 equably with numeral order, and the output valve of numbering " 0 " to " 39 " is increased to 15 equably with numeral order.In this case, compare with the above-mentioned multistage dithering process (output valve is increased to 15 from 1) that is used for fringe region, though the heterogeneity of high density (being not less than 13) is bigger, sawtooth is inconspicuous.
Output tint correction part 18 is carried out output calibrations and is handled, and density signal etc. is converted to half-tone regions ratio as the characteristic value of image output device 34.Because the input-output relation of output tint correction (before the conversion and the relation afterwards) be based on the characteristic of image output device 34 and determine by the processing that carry out tone rendering processing section 19, therefore usually, when the multistage dithering process of carrying out by tone rendering processing section 19 not simultaneously, be necessary to change the input-output relation of output tint correction according to multistage dithering process.For example, when utilizing checking list (tint correction information) to carry out the output tint correction, a plurality of checking lists are necessary.But, input-output relation as the output tint correction, only use and the corresponding input-output relation of the multistage dithering process that is used for the zone except that the zone, edge, and this input-output relation can be used to fringe region and the zone except that the zone, edge.When this relation be used to described zone both the time because the required memory span of storage checking list is littler, and does not carry out the switching of checking list, so the part of the switching of the higher and checking list of processing speed is difficult to discover more.
Be arranged in the shake matrix input value (input density value) and the total relation between the output valve by output characteristic according to image output device 34, can when the multistage dithering process of tone rendering processing section 19, carry out the output tint correction of output tint correction part 18 simultaneously and handle.Figure 11 is the view that is illustrated in the example of the relation between the input value and total output valve in the dither matrix in the zone except that the zone, edge.In Figure 11, input value is 0 to 255, and the total output valve in the dither matrix is 0 to 600 (15 * 40 pixel=600 of every pixel output valve).Based on the relation between input value and the total output valve, be provided with ten five threshold values corresponding and 16 output valves to (pairs) with the zone.As be used for the input value of multistage dithering process of fringe region and the relation between total output valve, can use the input value of the multistage dithering process that is used for the zone except that the zone, edge and the total relation between the output valve same as before.
Though in the present embodiment, described the dither matrix that comprises a plurality of submatrixs as shown in Figure 1 as an example, submatrix quantity is arbitrarily, and a submatrix can be used as dither matrix.Figure 12 is the view of another example that expression is used for the dither matrix of multistage dithering process.Figure 13 is the view of the example of expression from low-density to highdensity output valve.Submatrix that the dither matrix of Figure 12 comprises a plurality of (among the figure being two).Numeral in the grid (numbering) representative distributes the order of higher output valve, and the digitized representation output valve in the grid of Figure 13.
At the dither matrix that comprises four submatrixs as shown in Figure 1 with comprise that the switching between the dither matrix of two submatrixs as shown in figure 12 can carry out according to the zone.Comprise that more the dither matrix of the submatrix of smallest number has more advantage on size and cost savings, because its needed memory span is littler.
(second embodiment)
Figure 14 is that expression comprises the block diagram according to the example of structure of the image formation system of image processing equipment of the present invention.This image formation system has computer (image processing equipment) 50 and printer (image output device, image forming apparatus) 56.Printer 56 can carry out colour output, and can be the digital multifunction apparatus with copy function and facsimile function and printer function.Printer 56 forms according to xerography or ink-jet method carries out image.
For example, view data is input to computer 50 from image reading apparatus or the digital camera such as dull and stereotyped (flatbed) scanner or Film scanner, stores the unshowned storage device such as hard disk then into.The view data that is input to computer 50 can be come processed and editor by carrying out various application programs.Computer 50 is as dividing processing part 51 work in the zone under the pixel of the output image data of determining to output to printer 56; Carry out halftoning and produce the tone rendering processing section 53 of handling; With the printer language translator unit 54 that output image data is converted to printer language.Dividing processing part 51 is carried out and the similar dividing processing of being carried out by the dividing processing part 14 of the image processing equipment 10 of above-mentioned first embodiment of dividing processing (zone is determined to handle).Tone rendering processing section 53 is carried out to generate with the halftoning of being carried out by the tone rendering processing section 19 of the image processing equipment 10 of first embodiment and is handled similar halftoning and generate and handle (dithering process).Though not shown, computer 50 can be carried out with the colour correction part 15 of the image processing equipment 10 of first embodiment, black generates and undercolour removal part 16, space filtering processing section 17 and output tint correction part 18 are similarly handled.The data that are converted to printer language by printer language translator unit 54 are output to printer 56 by communication port 55 (Centronics port, LAN (local area network (LAN)) port etc.).
Figure 15 is the block diagram of the example of expression computer configuation.Computer 50 has CPU 61, RAM (random access memory) 62, hard drive (being abbreviated as hard disk later on) 63, such as the external memory 64 of floppy disc or CD-ROM (Compact Disc-Read Only Memory) and control the communication port of communicating by letter 55 with printer 56 etc.And computer 50 has such as the importation 65 of keyboard and mouse and such as the display part 66 of CRT (cathode ray tube) display or LCD.Communication port 55 comprises network interface card or modulator-demodulator, can be connected with the communication network such as LAN, internet and telephone wire.
The above-mentioned parts 62 to 66 and 55 of CPU 61 controls.And, CPU 61 will be from the importation 65 or communication port 55 program or the data accepted, perhaps program that reads from hard disk 63 or external memory 64 or storage are to RAM 62, execution is stored in the program among the RAM 62 or carries out processing such as data manipulation, and stores result or the ephemeral data that is used to handle into RAM 62.Be stored in that data such as result among the RAM 62 are stored in hard disk 63 by CPU 61 or from the display part 66 or communication port 55 outputs.
CPU 61 is as dividing processing part 51, tone rendering processing section 53 and 54 work of printer language translator unit.For example, view data is input to computer 50 from scanner or digital camera, and stores hard disk 63 into.And CPU 61 selects part (selector) 44 work as threshold process part 42 and the threshold value of first embodiment (Fig. 7).RAM 62 or hard disk 63 are as threshold value output storage area (memory) 46 work.
By by external memory 64 reading and recording such as the computer program on the recording medium 69 of CD-ROM, it is stored in hard disk 63 or RAM 62, and carries out these computer programs by CPU 61, can make computer 50 as above-mentioned parts work.And, can carry out by the communication port 55 that is connected to LAN etc. and accept computer program, and it is stored among hard disk 63 or the RAM 62 from another equipment.The computer program that realization is handled (dithering process) according to tone rendering of the present invention can be included in the printer driver, perhaps can be included in the application software that is used for image processing.
Figure 16 is the flow chart of the example of expression dithering process program.CPU 61 determines the zone under the pixel to be processed, and will determine that the result stores RAM 62 into.As definite result (S10: be) when the fringe region, CPU 61 read from hard disk 63 be used for fringe region threshold value to (S12), and they are stored in RAM 62.When determining the result (S10: deny) for regional except that the zone, edge, CPU 61 read from hard disk 63 be used for the zone except that the zone, edge threshold value to (S14), and store them into RAM62.Threshold value that CPU 61 relatively reads and pixel value to be processed read output valve (S16) based on threshold value comparative result (which is bigger) from hard disk 63, and are stored to RAM 62.Above-mentioned processing is carried out (S18: not) to all pixels.Be similar to that the first embodiment execution area is determined, threshold value is selected and output valve is selected.
(the 3rd embodiment)
Though threshold value is used to carry out many-valued dithering process in the above-described embodiments, also can carry out multistage dithering process by utilizing conversion table (contacts list).Figure 17 is the block diagram of another example of structure of the relevant portion of expression tone rendering processing section 19.Tone rendering processing section 19 has conversion portion 43, table is selected part 45 and conversion table storage area 47.Conversion table storage area 47 is stored in the input value (input pixel value) of the dithering process of the threshold value of utilizing first embodiment and the contact (conversion table) between the output valve.Stored conversion table is according to determining that such as the zone in fringe region (for example, character zone) and the zone except that the zone, edge (for example, half-tone regions, printing paper zone and page layout background zone) result classifies.
Cut apart sorting signal and be imported into table selection part 45, and based on cutting apart sorting signal, table selects part 45 to select the conversion table that is used for the conversion table of fringe region or is used for the zone except that the zone, edge, and it is read and be transferred to conversion portion 43 from conversion table storage area 47.Though in the present embodiment, the conversion table that is used for the zone except that the zone, edge is used to belong to the pixel of half-tone regions, also can prepare to be used for the conversion table of half-tone regions, so that selected and use under the situation of half-tone regions.For input image data (input value), conversion portion 43 is based on the output image data (output valve) according to the conversion table output correspondence of cutting apart the sorting signal selection.In this case, owing to there is not the comparison of execution and threshold value, therefore can carry out dithering process at a high speed.Yet the memory capacity that is used for conversion table is essential.
(the 4th embodiment)
Similar above-mentioned second embodiment can make tone rendering processing section 19 work of computer as the 3rd embodiment.Figure 18 is the block diagram of the example of expression computer configuation.Though the structure of computer 50 and second embodiment's (Figure 15) is similar, but be recorded in the computer program difference on the recording medium 69, and, can make tone rendering processing section 19 work of computer as the 3rd embodiment by reading this computer program by external memory 64 and carrying out this program.In the present embodiment, CPU 61 selects part (selector) 45 work as conversion portion 43 and the table of the 3rd embodiment (Figure 17).RAM62 or hard disk 63 are as conversion table storage area (memory) 47 work.
Figure 19 is the flow chart of another example of expression dithering process program.CPU 61 determines the zone under the pixel to be processed, and will determine that the result stores RAM 62 into.As definite result (S20: be) when the fringe region, CPU 61 read be used for fringe region conversion table (contact data) (S22), and be stored to RAM 62.When determining the result (S20: deny) for regional except that the zone, edge, CPU 61 from hard disk 63 read be used for the zone except that the zone, edge conversion table (contact data) (S24), and be stored to RAM 62.CPU 61 determines and the corresponding output valve of pixel value to be processed (S26) based on the conversion table that reads, and is stored to RAM 62.All pixels are carried out above-mentioned processing (S28: not).Be similar to that the 3rd embodiment execution area is determined, conversion table is selected and output valve is selected.
Though as described in the second and the 4th embodiment, the computer program that computer is carried out according to tone rendering processing of the present invention (dithering process) is stored in the storage medium, but storage medium can be a kind of unshowned memory, for example, such as the program medium of ROM so that carry out this processing by microcomputer, perhaps can be a kind of program medium, can wherein read by providing such as the program reader of external memory 64 and with the recording medium insertion.Under any circumstance, also can adopt a kind of like this structure, accessed its microprocessor of institute's program stored is carried out, perhaps can adopt a kind of like this method, program is read, and the program that is read is downloaded to the program storage area of unshowned microcomputer then, and this program is performed.In this case, the program that be downloaded is pre-stored in the equipment.
Program medium is a kind of recording medium that is separated with main body that is constituted as, and can be a kind of medium, carry (fixedly carrying) program regularly, comprising: such as the belt of tape (magnetic tape) and cassette tape (cassette tape); Disk such as floppy disc and hard disk; Such as the dish of CD, for example, CD-ROM, MO (magneto-optic) dish, MD (mini-disk), DVD (digital versatile disc); Card such as IC (integrated circuit) card (comprising storage card) and light-card; And semiconductor memory, such as mask rom, EPROM (erasable programmable ROM), EEPROM (electrically erasable ROM) and flash ROM.
Can be connected in system configuration under the situation of the communication network that comprises the internet, program medium can be a kind of medium that fluidly carries (fluidly carrying) program, such as from the downloaded program.When like this by the downloaded program, the program that download can be pre-stored in the equipment or can be installed from another recording medium.
(the 5th embodiment)
Though in above-mentioned first embodiment, under the situation of edge region, as shown in Figure 9 for each submatrix, output valve as the numbering of core is increased to 15 from 1, and under the situation in the zone except that the zone, edge, output valve increases equably with numeral order, in multistage dithering process for fringe region, replace at first the output valve as the numbering of core (starting point) of all submatrixs is increased to predetermined value, have only output valve at first to be increased to predetermined value as the numbering of the core (starting point) of predetermined submatrix.
Figure 20 is the view of another example of expression from low-density to highdensity output valve.In dither matrix as shown in Figure 1, by the relation between the threshold value of the following multistage dithering process that is used for fringe region:
Th[i][j]≤Th[i+1][j]
Th[1][j]≤Th[0][j+1]
Th[1][14]≤Th[2][0]
Th[39][j]≤Th[2][j+1]
As shown in figure 20, from low-density (upper left side of Figure 20) to high density (lower right of Figure 20), be increased to 15 as the output valve of the numbering " 0 " of two core in four submatrixs and " 1 " from 1, and the output valve of other numberings increases equably with numeral order.For example, be increased to after 15 from 1 as the numbering " 0 " of the core (starting point) of two submatrixs and the output valve of " 1 ", the output valve of numbering " 2 " to " 39 " is increased to 1 with numeral order, and the output valve of numbering " 2 " to " 39 " is increased to 15 from 2 equably according to numeral order in a similar fashion then.Thereby, because each submatrix all comprises the output valve of 38 pixels in 40 pixels of four submatrixs of ten pixels and equates basically with respect to the input density value, so can fabulous reproducibility be arranged and suppressed the image of sawtooth to character part and fine rule part output device.
For the multistage dithering process that is used for fringe region, can use diverse ways.Figure 21 is the view of another example of expression from low-density to highdensity output valve.In dither matrix as shown in Figure 1, by the relation between the following threshold value:
Th[i][j]≤Th[i+1][j]
Th[1][j1]≤Th[0][j1+1]
Th[1][9]≤Th[2][0]
Th[39][j1]≤Th[2][j1+1]
Th[39][j2]≤Th[0][j2+1]
(j1=0,1,2 ..., 8, perhaps j2=9 ..., 13)
As shown in figure 21, from low-density (upper left side of Figure 21) to high density (lower right of Figure 21), be increased to 10 as the numbering " 0 " of two core in four submatrixs and the output valve of " 1 " from 1, and the output valve of other numbering evenly is increased to 10 with numeral order, all is increased to 15 equably then.For example, be increased to after 10 from 1 as the numbering " 0 " of the core (starting point) of two submatrixs and the output valve of " 1 ", the output valve of numbering " 2 " to " 39 " is increased to 1 with numeral order, then in a similar fashion, the output valve of numbering " 2 " to " 39 " is increased to 10 from 2 equably with numeral order, and the output valve of numbering " 0 " to " 39 " then is increased to 15 from 11 equably with numeral order.In this case, compare with the above-mentioned multistage dithering process that is used for fringe region (output valve of " 0 " and " 1 " at first is increased to 15 from 1), though the inhomogeneities of high density (being not less than 10) is bigger, sawtooth is inconspicuous.
Hope is in a plurality of submatrixs, the submatrix of selecting wherein the output valve as the numbering of core at first to be increased, so as from as the pixel of the numbering " 1 " of the core of submatrix to as the distance (arrow the figure) of the pixel of the numbering " 0 " of the core of submatrix on every side with shown in Figure 22 identical.The submatrix that is at first increased for the output valve of selecting as the numbering of core, though described distance is possible (referring to Figure 24 that the method that increases output valve is shown) with different arrangement shown in Figure 23, but when described distance with shown in Figure 22 when identical, the position inhomogeneities that can suppress the tone characteristic of fringe region can suppress simultaneously the reduction of the picture quality that causes owing to the right switching of a plurality of threshold values.

Claims (16)

1. image processing method is wherein based on carrying out the dithering process of utilizing dither matrix to the definite result of cutting apart classification under the pixel to be processed, wherein
Have the right identical configuration of a plurality of threshold values and the dither matrix of same size by use, according to definite result of cutting apart classification is carried out different dithering process to the part of dither matrix.
2. image processing method, wherein based on the definite result of cutting apart classification under the pixel to be processed is carried out the dithering process of utilizing dither matrix, described method comprises step:
According to cutting apart definite result of classification, select to comprise any dither matrix in a plurality of dither matrixs of combination of dither matrix of the identical configuration of varying number and same size; With
According to cutting apart definite result of classification, the part of the dither matrix that is included in configuration in the selected dither matrix, identical and same size is carried out different dithering process.
3. according to the image processing method of claim 1 or 2, wherein
In order to carry out dithering process, according to selecting any threshold value of a plurality of threshold value centerings right to definite result of cutting apart classification, and the selected threshold value pair value with pixel to be processed is compared, wherein said threshold value is to being configured such that each position corresponding to the dither matrix of identical configuration and same size, according to definite result of cutting apart classification is carried out different dithering process to the part of dither matrix, and no matter how definite result of cutting apart classification is carried out identical dithering process to the remainder of dither matrix.
4. according to the image processing method of claim 3, wherein
According to whether being that fringe region selects described threshold value right to definite result of cutting apart classification.
5. according to the image processing method of claim 1 or 2, wherein
According to pixel value to be processed, no matter how to definite result of cutting apart classification, all with the position identical with position with other threshold value as starting point, increase as pixel value the dithering process result of each position with a dither matrix threshold value, identical configuration and same size.
6. according to the image processing method of claim 5, wherein
When definite result of cutting apart classification is fringe region, according to pixel value to be processed, the pixel value of the starting point of the dither matrix of identical configuration and same size is increased to predetermined value, and the pixel value with other position of dither matrix is increased to predetermined value equably then.
7. according to the image processing method of claim 5, wherein
When a plurality of dither matrixs of identical configuration and same size constitute one group, and when definite result of cutting apart classification is fringe region, according to pixel value to be processed, the pixel value of the predetermined starting point of the starting point of dither matrix is increased to predetermined value, then other starting point of dither matrix and the pixel value of other position is increased to predetermined value equably.
8. according to the image processing method of claim 7, wherein
Described predetermined starting point is distributed equably.
9. according to the image processing method of claim 5, wherein
When definite result of cutting apart classification is not fringe region, according to pixel value to be processed, the pixel value of the starting point of the dither matrix of identical configuration and same size is increased to predetermined value, and ground, position is increased to predetermined value with the pixel value of other position of dither matrix one by one then.
10. according to the image processing method of claim 1 or 2, wherein
Based on the total tint correction information and executing tint correction of pixel, and no matter to definite result of cutting apart classification how.
11. according to the image processing method of claim 1 or 2, wherein
In order to carry out dithering process, according to the arbitrary data in a plurality of data that definite option table as a result of cutting apart classification are shown in pixel value before the dithering process and the relation between the pixel value after the dithering process, and value according to the data transaction pixel to be processed of the described contact of selected expression, wherein, described data are set so that according to definite result of cutting apart classification is carried out different dithering process to the part of the dither matrix of identical configuration and same size, and no matter how definite result of cutting apart classification are carried out identical dithering process to the remainder of dither matrix.
12. an image processing equipment, it is based on utilizing dither matrix to carry out dithering process to the definite result of cutting apart classification under the pixel to be processed, and described equipment comprises:
Storage area, it is right that it stores a plurality of threshold values, these threshold values are to being configured such that each position corresponding to the dither matrix of identical configuration and same size, according to definite result of cutting apart classification is carried out different dithering process to the part of dither matrix, and no matter how definite result of cutting apart classification is carried out identical dithering process to the remainder of dither matrix; With
Select part, it is right according to any threshold value that definite result's selection of cutting apart classification is stored in the described threshold value centering in the described storage area,
Wherein, in order to carry out dithering process, will pair compare by the threshold value of described selection portion component selections with pixel value to be processed.
13. an image processing equipment, it is based on utilizing dither matrix to carry out dithering process to the definite result of cutting apart classification under the pixel to be processed, and described equipment comprises:
Storage area, the pixel value of its storage representation before dithering process and a plurality of data of the relation between the pixel value after the dithering process, these data are configured such that according to definite result of cutting apart classification is carried out different dithering process to the part of the dither matrix of identical configuration and same size, and no matter how definite result of cutting apart classification is carried out identical dithering process to the remainder of dither matrix; With
Select part, it is according to the arbitrary data in the data of definite result of cutting apart classification being selected the described relation of expression in the described storage area that is stored in,
Wherein, in order to carry out dithering process, based on value by the data transaction pixel to be processed of the described relation of expression of described selection portion component selections.
14. an image forming apparatus comprises:
Image processing equipment according to claim 12 or 13; With
Image output device, it forms the image of being handled by described image processing apparatus on paper.
15. a recording medium has wherein write down computer program, is used for based on the definite result of cutting apart classification under the pixel to be processed being utilized dither matrix carry out dithering process, described computer program comprises step:
Make computer according to selecting any threshold value of a plurality of threshold value centerings right to definite result of cutting apart classification, these threshold values are to being configured such that each position corresponding to the dither matrix of identical configuration and same size, according to definite result of cutting apart classification is carried out different dithering process to the part of dither matrix, and no matter how definite result of cutting apart classification is carried out identical dithering process to the remainder of dither matrix; And
Make described computer that the selected threshold value pair value with pixel to be processed is compared, so that carry out dithering process.
16. a recording medium has wherein write down computer program, is used for based on the definite result of cutting apart classification under the pixel to be processed being utilized dither matrix carry out dithering process, described computer program comprises step:
Make computer according to the arbitrary data in a plurality of data that definite option table as a result of cutting apart classification are shown in pixel value before the dithering process and the relation between the pixel value after the dithering process, these data are configured such that according to definite result of cutting apart classification is carried out different dithering process to the part of the dither matrix of identical configuration and same size, and no matter how definite result of cutting apart classification is carried out identical dithering process to the remainder of dither matrix; And
Make described computer based in the value of the data transaction pixel to be processed of the described relation of selected expression, to carry out dithering process.
CNB2006100770454A 2005-04-26 2006-04-26 Image processing method, image processing apparatus, image forming apparatus, and recording medium Expired - Fee Related CN100452827C (en)

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US6582046B1 (en) * 1998-12-25 2003-06-24 Copyer Co., Ltd. Method and device for image processing
JP2001257893A (en) * 2000-03-09 2001-09-21 Sharp Corp Method and device for image processing and computer- readable recording medium with recorded image processing program
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