CN1172263C - Frequency modulation Internet access method for copying images on multiple position imaging depth equipment - Google Patents
Frequency modulation Internet access method for copying images on multiple position imaging depth equipment Download PDFInfo
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Abstract
The present invention relates to a frequency modulation Internet access method for copying images on multiple-position imaging depth equipment. The method of the prior art is that after inputted image data is converted into one-position equipment output image data, the one-position data is munaully and forcibly converted into image data needed by corresponding-position depth equipment such as general two-position depth lattice data; then, the data is outputted. On the basis of a traditional error diffusion frequency modulation Internet access technique, the present invention uses a multi-threshold value error diffusion technique, adopts different diffusion parameters to different image hierarchies, and combines with random disturbance for directly outputting the image output data needed by multi-position depth equipment. The method of the present invention can be adopted for largely improving imaging quality to make the transition of the image hierarchies smooth. The distribution of websites of each hierarchy is uniform, and a touches part is exquisite.
Description
Technical field
The present invention relates to a kind of image hard copy and duplicate the site generation method in field, be specifically related to a kind of net hanging method that on the equipment of multi-position imaging depth, carries out copying image.
Background technology
The linked network plate-making technology that relates generally to printer and high-grade plate making equipment is duplicated in the hard copy of image.Be used for the screening technology that the image hard copy duplicates and be called the digital picture halftone technique again.The digital picture halftone technique can be divided into two classes, is respectively amplitude modulation screening and frequency-modulation screening.Amplitude modulation screening is called convergence point ordered dithering technology again, the stain that it is characterized in that the half tone image that generated is adjacent to condense together on the geometric position in twos, thereby formed the pigmented section of cluster cluster, these pigmented section site that is otherwise known as, because convergence point ordered dithering technology adopts the network point Method for Area to reproduce the original image gray scale, thereby is called as the amplitude modulation site.
Opposite with amplitude modulation screening, the frequency modulation half tone image is avoided the gathering of stain on the geometric position as far as possible in the process of its generation.It realizes the gray-scale rendition of original image by the number of stain in the control unit area.Because being the form with non-gathering, the stain in the frequency modulation half tone image distributes, therefore to different original copy gray levels, will be corresponding to the mean distance between the different stain, angle from Digital Image Processing, the frequency that promptly is image changes, the origin of the noun of Here it is frequency-modulation screening.In the process that generates the frequency modulation half tone image, because stain is being distributed on the image of isolating, so for the fixing original image zone of gray scale, the distribution of stain must guarantee very even, that is the distance between each stain and its neighbour's stain must very approaching foregoing mean distance, so just can avoid harmful texture that may occur.
In traditional frequency-modulation screening method, error diffusion method is the most frequently used method.Document " Dithering with blue noise ", (Robert A.Ulichney, Proceddings of The IEEE, Vol.76, No.1, January 1988, pp56-79) disclose a kind of error diffusion method, and its principle can be explained with accompanying drawing 1.In the processing procedure of error diffusion algorithm, pixel g (the m of original image, n) sequentially handled line by line, in the process of handling, each pixel is carried out threshold operation (quantizer Quantizer) with a fixing threshold value, the result of computing be converted into half tone image respective pixel b (m, n).Meanwhile, with this as a result pixel b (m, n) and asked the pixel g of threshold value (m n) compares, and (m n) diffuses on the not processed pixel around the current processed pixels with a diffusion filter (Error filter) with the difference e of relatively trying to achieve.In processing subsequently, the pixel value of being asked threshold value be original copy pixel g (m, n) and be flooded to error on this pixel and.Below, we introduce the calculating process of disclosed error diffusion method in the above-mentioned document.Algorithm 1: the citation form of error diffusion:
The wide height of supposing the original image N that treats linked network is w, h, and this algorithm is converted into this image the frequency modulation shadow tone binary map B of same size.
For (i=0; I＜h; I++) For (j=0; J＜w; J++) { the former pictorial data of lining by line scan is got (i, the visual pixel value of j) locating: p=Nij; If (p＞127) Bij=255; Else Bij=0; Calculate the error of input brightness with respect to output brightness: Err=Nij-Bij; This error (Err) be multiply by the coefficient of diffusion filter respectively, then respectively with the original image pixel addition of relevant position, and the result replaced the corresponding pixel value of original image; }
Be to use fixing diffusion parameter in actual use, for example, the normal parameter of using is:
d1＝1 d2＝2 d3＝5 d4＝4 d5＝8
Modulating net image quality according to above-mentioned algorithm realization, test by reality, obtain accompanying drawing 2, in the distribution of the regional site of shallow accent, have the frequency modulation point of a large amount of regular distribution as can be seen from Figure 2, make that the site to occur at some level coarse, cause gradual change excessively bad, level is not fully withdrawn, and does not reach practical level.Therefore find out that this frequency modulation algorithm exists potential deficiency.
In addition, be not difficult to find out from above-mentioned algorithm, the level that the site of tradition modulating net can be reproduced has only the embodiment of two levels, both 255 (white points), 0 (stain), be directed on the equipment of an imaging depth, be feasible, but on the equipment of multi-position imaging depth, if still generate frequency-modulation halftone dot according to this algorithm, the one, can not embody the abundanter level effect that multi-position imaging depth device can show, the 2nd, because the change of the equipment image-forming mechanism of multi-position imaging depth finally also can change the regularity of distribution of a frequency-modulation halftone dot more or less, thereby influence output quality.
Summary of the invention
The objective of the invention is at traditional error diffusion method in the second-rate defective of reality output frequency-modulation halftone dot, proposed a frequency-modulation screening method that is applicable to multi-position imaging depth device, thereby finally reached the effect that on multi-position imaging depth device, produces high-quality frequency-modulation halftone dot based on traditional error diffusion algorithm.
For reaching above purpose, the technical solution used in the present invention is: a kind of frequency-modulation screening method that carries out copying image on the equipment of multi-position imaging depth may further comprise the steps:
1) input original image, to the pixel g of original image (m n) carries out threshold operation, the result of computing be converted into the respective pixel b of half tone image (m, n);
When carrying out threshold operation, the threshold value number is not fixed, but determines that by the imaging depth of output device imaging depth is the equipment of n, and the gray-level that can reproduce is 2
nIndividual, corresponding threshold also has 2
nIndividual, realize the linked network result of the multidigit degree of depth by adopting the method for setting a plurality of threshold values; And, when carrying out computing, also to make random processing to preset threshold, in each use threshold value, all add a random number, random number is an integer between [8 8];
2) with b (m, n) and asked threshold value pixel g (m n) compares, and try to achieve both differences be error e (m, n);
3) with error e (m n) diffuses on the not processed pixel around the current processed pixels with a diffusion filter, the pixel value of promptly being asked threshold value be original copy pixel g (m, n) and be flooded to error on this pixel and;
With error to three pixels diffusion that closes on, be respectively the next consecutive point of next consecutive point, these row of one's own profession and lower left to consecutive point; Carrying out the weight allocation ratio of error diffusion can regulate to these points, reaches by the weight allocation ratio of regulating different error amounts and improves the purpose that frequency-modulation halftone dot distributes;
4) to the pixel g of original image (m according to the sequential processes of changing direction line by line, repeats above step when n) handling, up to all pixel g of original image (m, n) processed intact, form the half tone image of original image at last;
In order to have better effect, the setting of threshold value is a five equilibrium not in the step 1), and promptly when dividing the level zone, the panchromatic accent area dividing with 0 to 255 becomes not a plurality of zones of five equilibrium, and the imaging bit depth that what of zone can be supported by equipment is determined.
Effect of the present invention is: by method of the present invention, can be at the modulating net image of supporting outputting high quality on the equipment of multi-position imaging depth, can effectively improve traditional modulating net the intrinsic systematicness site deficiency of arranging, improve the irreproducible image level of modulating net, make the image of equipment output can greatly satisfy the requirement of actual print digital sample printing qualitatively at color and level.
Description of drawings
Fig. 1 is the disclosed error diffusion method principle schematic of documents;
Fig. 2 is modulating net site gradual change synoptic diagram of tradition;
Fig. 3 is the error diffusion filter schematic;
Fig. 4 is the modulating net of a bit depth and the modulating net comparison diagram of two bit depth;
Fig. 5, Fig. 6 are 0 to 100% step-wedge linear gradient comparison diagrams, and wherein Fig. 5 is modulating net step-wedge gradual change synoptic diagram of tradition, and Fig. 6 is two modulating net step-wedge gradual change synoptic diagram after improving;
Fig. 7, Fig. 8 are 0 to 70% step-wedge linear gradient comparison diagrams, and wherein Fig. 7 is modulating net step-wedge gradual change synoptic diagram of tradition, and Fig. 8 is two modulating net step-wedge gradual change synoptic diagram after improving;
Fig. 9, Figure 10 are 0 to 50% step-wedge linear gradient comparison diagrams, and wherein Fig. 9 is modulating net step-wedge gradual change synoptic diagram of tradition, and Figure 10 is two modulating net step-wedge gradual change synoptic diagram after improving.
Embodiment
Below in conjunction with accompanying drawing the present invention is done to describe further: a kind of frequency-modulation screening method that carries out copying image on the equipment of multi-position imaging depth may further comprise the steps:
1) input original image, to the pixel g of original image (m n) carries out threshold operation, the result of computing be converted into the respective pixel b of half tone image (m, n);
When carrying out threshold operation, the threshold value number is not fixed, but determines that by the imaging depth of output device imaging depth is the equipment of n, and the gray-level that can reproduce is 2
nIndividual, corresponding threshold also has 2
nIndividual, realize the linked network result of the multidigit degree of depth by adopting the method for setting a plurality of threshold values; And, when carrying out computing, also to make random processing to preset threshold, in each use threshold value, all add a random number, the random number that is added is an integer between [8 8];
2) with b (m, n) and asked threshold value pixel g (m n) compares, and try to achieve both differences be error e (m, n);
3) with error e (m n) diffuses on the not processed pixel around the current processed pixels with a diffusion filter, the pixel value of promptly being asked threshold value be original copy pixel g (m, n) and be flooded to error on this pixel and;
As shown in Figure 3, with error to three pixels diffusion that closes on, be respectively the next consecutive point of next consecutive point, these row of one's own profession and lower left to consecutive point; Carrying out the weight allocation ratio of error diffusion can regulate to these points, reaches by the weight allocation ratio of regulating different error amounts and improves the purpose that frequency-modulation halftone dot distributes;
4) (m according to the sequential processes of changing direction line by line, repeats above step when n) handling, and (m, n) processed finishing forms the half tone image of original image at last up to all pixel g of original image at the pixel g to original image.
The included step of this method can be referring to following algorithm:
2: two imaging modulating nets of algorithm algorithm:
The width of supposing the original image N that treats linked network is w * h, because what adopted here is two imagings, therefore the level that can reproduce at a frequency-modulation halftone dot have 2 n power individual, hierachy number at this should reach 4, that is: 0 (00), 1 (01), 2 (10), 3 (11), the data in the bracket are binary expressions, also can be described as the representation on the equipment.At the area dividing of above-mentioned level, for ease of explanation, suppose here panchromatic accent be divided into three gradient: 0-R1, R1-R2, and R2-255,, each region threshold is assumed to: M1, and M2, its corresponding relation of dividing in level of M3 should be:
0 --0(00)， R1 --1(01)，
R2 --2(10)， 255 --3(11)，
In view of the above, we can do following improvement with a traditional modulating net algorithm.Thereby reach the characteristic of two frequency modulation imagings.
| For (i=_0; I＜h; I++) For (j=0; J＜w; J++) { get (i, the visual pixel value of j) locating: the p=Nij if (Bij=0 of p＜M1); Else if (the Bij=R1 of M1＜=p＜R1-1); Else if (the Bij=R1 of R1＜=p＜M2); Else if (the Bij=R2 of M2＜=p＜R2-1); Else if (the Bij=R2 of R2＜=p＜M3); Else if (M3＜=p＜=255) Bij=255; Calculate the error of input brightness with respect to output brightness: Err=Nij-Bij multiply by this error (Err) respectively the coefficient of diffusion filter, then respectively with the original image pixel addition of relevant position, and the result replaced the corresponding pixel value of original image; }
Top method can be promoted just can realize multi-position imaging modulating net algorithm, but we find from practice, simple going is modified into two or multidigit modulating net with a modulating net, though satisfied the requirement of equipment, but because the deficiency that itself exists on the algorithm must not have great improvement to final net-point quality, we are by four kinds of following innovative approachs for this reason, originally improved on one's body from algorithm, make the idea of frequency modulation output obtain qualitative leap:
Innovative approach one: the not five equilibrium of threshold setting
The method of mentioning in the algorithm 2 of dividing equally whole level zone, because imaging device uses the printing ink of variable concentrations or volume usually, toner or other colour generation material embody different imaging depths, ratio between the different imaging depths may be uneven, therefore, therefore the setting of the FM threshold of multi-position imaging also can be arranged to uneven, be that we are when dividing the level zone, can be according to the characteristic of output device, panchromatic accent area dividing with 0 to 255 becomes not a plurality of zones of five equilibrium, and the imaging bit depth that how much can be supported by equipment in zone is determined.
Innovative approach two: threshold value shake mechanism
Threshold setting in traditional error diffusion algorithm is that the mid point by the level zone decides, and normally constant, and we have adopted the method for threshold value random number disturbance at this, its method is, in each use threshold value, all add a random number, the scope of random number is [8 8].Its objective is by the effect of random number and remove the regular lines that occurs easily at some gray-level, make output image in all even irregular distribution in the site at all levels.This point can be by following algorithmic descriptions
Algorithm 3: based on threshold value shake and each different in nature error diffusion algorithm of error diffusion coefficient
For ease of explanation, we use the algorithm of a frequency modulation for the time being here, and this algorithm is easy to expand in two or the multidigit error diffusion algorithm.The wide height of supposing the original image N that treats linked network is respectively w, h, and this algorithm is converted into this image the frequency modulation shadow tone binary map B of same size.
For (i=0; I＜h; I++) For (j=0; J＜w; J++) { the former pictorial data of lining by line scan is got (i, the visual pixel value of j) locating: p=Nij; If (p＞D[Rand (i, j)]) Bij=255; Else Bij=0; Calculate the error of input brightness with respect to output brightness: Err=Nij-Bij; This error (Err) be multiply by the coefficient of the diffusion filter among Fig. 3 respectively, then respectively with the original image pixel addition of relevant position, and the result replaced the corresponding pixel value of original image; }
D[Rand wherein (i, j)] be according to the difference of the position of visual pixel value at random in the threshold value dither table, obtain a current threshold value at random.As for definite method of threshold value dither table D, can realize by following algorithm:
Algorithm 4: threshold value dither algorithm
At first we set up a threshold value table F of [8,8], and determining of this table list item can be done random alignment according to 16 values in front and back of level zone mid point and form.Specifically how to obtain final D table, realize by following algorithm by table F:
Set reference mark: P1, P2, P3,
Parameter: d1, d2, d3 are adjusted in the shake of each reference mark correspondence
(the concrete control of setting is counted and corresponding value is set according to actual test result)
Parameter is adjusted in the shake of corresponding each level: d
j
For (i=0; I＜256; I++) { if (the interpolation result else if of dj=(0--d1) of i＜P1) (the interpolation result else if of dj=(d1-d2) of P1＜i＜P2) (interpolation result of dj=(d2-d3) of P2＜i＜P3) } formula below the di value substitution that obtains obtained the weight＜br/ of [8,8] the individual dithering threshold under the corresponding level〉new combination table D for (j=0; J＜32; J++) Djj=((Fj-hierarchy domain mid point) Xdj)+hierarchy domain mid point.
Innovative approach three: each opposite sex of error diffusion coefficient
The setting of the error diffusion coefficient in algorithm 1 and the algorithm 2 is certain, the change with gray-level does not change, and we to propose each opposite sex of coefficient of diffusion here be exactly to refer to poor between input image pixels value and the threshold value, as error, be to the pixel diffusion that closes on.Because the existence of each opposite sex, consider the efficient of actual linked network, so we just do not adopt the diffusion on 12 traditional directions yet, and adopt three diffusions on the direction, concrete dispersal direction is referring to the Fig. 3 in the accompanying drawing.When the point to these three directions spreads, coefficient of diffusion (weight allocation ratio just) is to regulate according to different error amounts, in concrete the enforcement, to each error amount, test different weight allocation ratios, and determine the weight allocation ratio that effect is best according to the frequency characteristic of final frequency-modulation halftone dot.
Innovative approach four: image pixel parity rows scan mechanism
So-called image pixel parity rows scan mechanism is meant and has adopted forward and reverse staggered method of carrying out on the processing sequence of input picture, for example, first line data individual element point is from left to right handled, and second line data is handled from right to left, the third line again from left to right, the rest may be inferred.Its effect is to offset because the systematicness on the error diffusion that horizontal sequential scanning pictorial data causes changes, and further eliminates the regular lines that some gray-levels occur easily.The specific implementation algorithm is as follows:
Algorithm 5: the error diffusion algorithm supposition based on visual parity rows scan mechanism treats that the wide height of the original image N of linked network is w h, and this algorithm is converted into this image the frequency modulation shadow tone binary map B of same size.
For (i=0; I＜h; I++) { if (i%2==0) { // even number line data processing For (j=0; J＜w; J++) { the former pictorial data of the every row of incremental scan is got (i, the visual pixel value of j) locating: p=Nij; If (p＞127) Bij=255; Else Bij=0; Calculate the error of input brightness with respect to output brightness: Err=Nij-Bij; This error (Err) be multiply by the coefficient of the diffusion filter among Fig. 3 respectively, then respectively with the original image pixel addition of relevant position, and the result replaced the corresponding pixel value of original image; Else { odd-numbered line data processing For (j=w-1; J＞=0; J--) { the former pictorial data of the every row of scanning of successively decreasing is got (i, the visual pixel value of j) locating: p=Nij; If (p＞127) Bij=255; Else Bij=0; Calculate the error of input brightness with respect to output brightness: Err=Nij-Bij; This error (Err) be multiply by the coefficient of the diffusion filter among Fig. 3 respectively, then respectively with the original image pixel addition of relevant position, and the result replaced the corresponding pixel value of original image;＜!--SIPO＜DP n=" 8 "〉--〉＜dp n=" d8 "/
Below all be to improve and improve the new modulating net algorithm that draws at the existing in prior technology deficiency.By above-mentioned improvement and optimized Algorithm, we have obtained meeting the effect of re-set target, following legend is the modulating net output effect that combines two bit depth of being done behind our all improvement algorithms, and we have adopted the legend of linear gradient figure linked network to illustrate, referring to accompanying drawing 4.
The modulating net of two bit depth has produced perfect frequency-modulation halftone dot through the optimized Algorithm that we realize as can be seen from accompanying drawing 4, and this point can compare with accompanying drawing 2.
Shown in accompanying drawing 5-accompanying drawing 7, here we make an example, suppose the modulating net of only making two imaging depths, parameter is provided with as follows: 0 to 255 grade level zone is divided into three region R 1=85, and R2=171, then the level area dividing is as follows: 0-85 (Rangel), 85-171 (Range2), 171-255 (Range3) gets each regional mid point and shakes basic point as threshold value, and then each level zone dither table is as follows before the shake:
Suppose that the dither table size is [8,8]
F1＝{45，39，43，38，45，46，41，40，39，44，43，44，40，38，41，46}，
F2＝{126，125，130，129，124，132，127，125，131，130，127，126，129，132，124，131}，
F3＝{215，212，210，211，214，209，216，212，217，210，216，214，215，217，211，209}；
In the threshold value shake, we set four reference mark, and we get this level zone of 0-85 here, can make corresponding getting final product: P1=24 owing to divide equally other zones of characteristic, P2=48, and P3=54.P4=64, corresponding shake is adjusted parameter and is set to:
Interval Range1 shake coefficient (d) Range2 shake coefficient (d) Range3 shake coefficient (d)
(0，24) 0.438 1.0 0.438
(24，48) 3.8 3.8 3.8
(48，54) 0.438 1.0 0.438
(54，64) 3.8 3.8 3.8
By behind the top parameter setting we made the modulating net of tradition in the different levels zone and improve after the reference diagram of two modulating nets contrasts, can be referring to accompanying drawing 5, Fig. 6, Fig. 7.
Claims (2)
1. frequency-modulation screening method that carries out copying image on the equipment of multi-position imaging depth may further comprise the steps:
1) input original image, to the pixel g of original image (m n) carries out threshold operation, the result of computing be converted into the respective pixel b of half tone image (m, n);
2) with b (m, n) and asked threshold value pixel g (m n) compares, and try to achieve both differences be error e (m, n);
3) with error e (m n) diffuses on the not processed pixel around the current processed pixels with a diffusion filter, the pixel value of promptly being asked threshold value be original copy pixel g (m, n) and be flooded to error on this pixel and;
4) repeat above step, up to all pixel g of original image (m, n) processed intact, form the half tone image of original image at last;
It is characterized in that:
(1) the threshold value number in the step 1) is not fixed, but determines that by the imaging depth of output device imaging depth is the equipment of n, and the gray-level that can reproduce is 2n, and corresponding threshold also has 2n;
(2) in step 1), preset threshold is made random processing, in each use threshold value, all add a random number, random number is an integer between [88];
(3) in step 3), with error to three pixels diffusion that closes on, be respectively the next consecutive point of next consecutive point, these row of one's own profession and lower left to consecutive point; Carrying out the weight allocation ratio of error diffusion can regulate to these points, reaches by the weight allocation ratio of regulating different error amounts and improves the purpose that frequency-modulation halftone dot distributes;
(4) in the step 4), (m according to the sequential processes of changing direction line by line, has promptly adopted forward and reverse staggered processing sequence of carrying out when n) handling at the pixel g to original image.
2. a kind of frequency-modulation screening method that on the equipment of multi-position imaging depth, carries out copying image as claimed in claim 1, it is characterized in that: the setting of threshold value is a five equilibrium not in the step 1), promptly when dividing the level zone, panchromatic accent area dividing with 0 to 255 becomes not a plurality of zones of five equilibrium, and the imaging bit depth that how much can be supported by equipment in zone is determined.
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| JP4396896B2 (en) * | 2005-01-07 | 2010-01-13 | 大日本スクリーン製造株式会社 | Threshold matrix generation method, threshold matrix generation apparatus, and recording medium |
| CN100385909C (en) * | 2005-02-03 | 2008-04-30 | 凌阳科技股份有限公司 | Error-diffusion half-tone image treatment system and method |
| JP4780374B2 (en) * | 2005-04-21 | 2011-09-28 | Ｎｋワークス株式会社 | Image processing method and program for suppressing granular noise, and granular suppression processing module for implementing the method |
| CN100338936C (en) * | 2005-04-27 | 2007-09-19 | 北京北大方正电子有限公司 | Double-feedback error diffusion based frequency-modulation screening method |
| CN100377567C (en) * | 2005-10-26 | 2008-03-26 | 北京北大方正电子有限公司 | FM and AM mixed net point net shape controlling method in multi-position imaging depth device |
| CN100435548C (en) * | 2006-09-15 | 2008-11-19 | 北京大学 | Method and device for generating multi-site modulating web site simultaneouslly |
| JP5345138B2 (en) * | 2007-06-08 | 2013-11-20 | トムソン ライセンシング | Method and apparatus for multi-grid sparsity-based filtering |
| CN101763628B (en) * | 2008-12-23 | 2011-11-16 | 北京大学 | Screening image boundary position smoothing method and device |
| CN101527774B (en) * | 2009-03-17 | 2011-01-05 | 北大方正集团有限公司 | Method for optimizing image lattice quality and device thereof |
| CN102263881B (en) * | 2010-05-24 | 2013-08-07 | 北大方正集团有限公司 | Method and device for processing halftone image frequency modulation mesh hanging |
| CN103139440B (en) | 2011-11-30 | 2015-06-17 | 北大方正集团有限公司 | Method and device for multi-bit-depth halftone amplitude modulation dot generating |
| CN102567971B (en) * | 2012-01-04 | 2013-12-18 | 上海理工大学 | Correction method for multiple error-diffusion half-tone |
| CN107948462A (en) * | 2017-11-24 | 2018-04-20 | 无锡祥生医疗科技股份有限公司 | Ultrasound image optimization method and system |
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