CN103400355A

CN103400355A - Method for extracting edge roughness characteristic of shaftless printing dot

Info

Publication number: CN103400355A
Application number: CN2013103621127A
Authority: CN
Inventors: 孔令罔
Original assignee: Wuhan University WHU
Current assignee: Wuhan University WHU
Priority date: 2013-08-19
Filing date: 2013-08-19
Publication date: 2013-11-20
Anticipated expiration: 2033-08-19
Also published as: CN103400355B

Abstract

The invention provides a method for extracting an edge roughness characteristic of a shaftless printing dot, and belongs to the field of printing image processing. The method particularly comprises the steps of inputting enhanced processing and shape characteristic resolving of a single dot image, extracting an edge and a central region of the dot, extracting a geometric center parameter and a shape parameter of the dot through Hough conversion, reconstructing the inputted dot with the extracted parameters, conducting exclusive or operation on the reconstructed dot and an enhanced binaryzation dot, extracting a dot crown structure, and outputting a dot crown structure spectrum, namely the edge roughness characteristic of the shaftless printing dot. The method solves the problem that the geometrical characteristic parameter of the dot, which is extracted based on a dot cluster is insufficient for describing a fine characteristic of the edge roughness of the practical printing dot currently, and provides a technological means for achieving dot-level product quality detection and analysis, and printing production control.

Description

A kind of method that realizes the feature extraction of shaftless printing net-point edge roughness

Technical field

The invention belongs to the printing images process field, particularly a kind of method that realizes the feature extraction of shaftless printing net-point edge roughness.

Technical background

The occasion that needs to extract the site geometric properties mainly contains typography control and print quality detection and analyzes, the geometrical characteristic parameter that at present printing net-point extracted all is aimed at by carrying out in zone that many sites form, i.e. geometrical characteristic parameter towards site bunch.Take typical amplitude modulation printing net-point as example, they are processed by the regional area to the collection halftone dot image, extract the geometrical characteristic parameters such as dot shape, site size, screen frequency, screen angle.

Printing is the coefficient technological process of multivariate, and the present site geometrical characteristic parameter that extracts is to be not enough to realize precision and the different levels print reproduction product quality of different printing duplication process are carried out precisely describing: the edge roughness site of low printing quality can be realized by the compensation of typography parameter and the geometric parameter values such as the identical dot shape of the bright and clean site, edge of high printing quality, site size, screen frequency, screen angle.This just makes the site geometrical characteristic parameter that extracts at present lose not the meaning of its fine-feature because describing precision.The solution of this problem need to be extracted the lattice point structure feature under small spatial scale more.

Summary of the invention

For the problem that background technology exists, for the lattice point structure feature under the small spatial scale of realizing the site level, describe, the inventor studies the method for shaftless printing net-point edge roughness feature extraction, and the present invention program produces thus.

The present invention realizes the extraction of its edge roughness feature to the shaftless printing net-point of current main-stream, with conventional site geometrical characteristic parameter under the solution Small-scale Space, describe the problem of precision deficiency.For realizing above-mentioned technology contents, scheme of the present invention comprises the steps:

Step 1, at first to the input site Dot _OrgCarry out greyscale transformation and obtain Dot _Gry, then to Dot _GryCarry out binary transform and obtain Dot _Bin, again to Dot _BinStrengthen processing, site Dot is enhanced _Enh

Step 2, to strengthening site Dot _EnhExtract edge Edg and calculate dot area Sqr, utilizing Edg and Sqr to resolve dot shape feature Shp;

Step 3, to strengthening site Dot _EnhExtract central area CA;

Edge Edg, central area CA and dot shape feature Shp that step 4, foundation are extracted, extract and strengthen site Dot by the Hough conversion _EnhGeometric center parameters C P and form parameter SP;

Dot shape parameter S P and geometric center parameters C P that step 5, utilization are extracted rebuild site, obtain rebuilding site Dot _Rec

Step 6, utilization strengthen site Dot _EnhWith reconstruction site Dot _RecCarry out XOR, extract site crown structure C S;

Geometric center point CP, dot shape parameter S P and site crown structure C S that step 7, utilization are extracted, obtain the crown structure spectrum CSS of site, thereby obtain shaftless printing net-point edge roughness feature.

In conventional typography, on stock, adhere to and fly Mo Mosi, in site, may there is simultaneously the situation of the construct noises such as cavity of hollow.Given this, need to strengthen processing to resulting two-value halftone dot image in described step 1 and with removal, fly the lattice point structure noises such as China ink, cavity.This enhancing processes that the opening and closing operation that is based on mathematical morphology carries out, and is that to obtain the simply connected region halftone dot image be mathematical morphology interative computation end condition.

Dot in step 2 _EnhThe extraction of edge Edg is to pass through Dot _EnhWith it, through single dot structure unit corrosion resulting image, carry out the difference realization.

The shaftless printing net-point of current main-stream has two kinds of square site and circular shaped lattice points, site Dot in step 2 _EnhDot shape feature Shp be by resolving Dot _EnhGirth square-Area Ratio differentiate: near 16 the time, Shp is square when girth square-area ratio; During near 4 π, Shp is circular when girth square-area ratio.

Site Dot in step 3 _EnhThe extraction of central area CA is to carry out the realization of iteration erosion operation by corresponding structural elements (wherein the structural elements shape dot shape feature Shp that must resolve with step 2 is consistent) is set.

Be directed to the some shape of two kinds of shaftless printing net-points of circular shaped lattice point and square site, the realization in step 4 need to adopt two kinds of different Hough to vary one's tactics:

(1), for circular shaped lattice point, need to set up the 5 tuple data structures that comprise central coordinate of circle, radius, counter and vote.According to voting results output geometric center parameters C P and the form parameter SP of its Counter, this moment, SP was radius value r;

(2), for square site, need to set up the two tuple data structures that comprise slope, intercept and vote.The voting results front two groups of slopes of output and 4 values of intercept according to counter.By two groups of slopes wherein, calculated two slope value of square site; Further calculate form parameter SP and geometric center parameters C P, this moment, SP was length of side value a.

The crown structure spectrum CSS of the site that step 7 obtains is by distance and the Dot of each edge pixel on crown structure C S envelope apart from site center C P _RecThe difference of radius calculates.

CSS is the reflection of the variable of many printing link to printed image data hard copy process synthesis exercising result.It provides on the printability bases such as specific ink, paper, galley, to the Indirect evaluation of printing process conditions and direct-detection and the evaluation index information of print quality.

Compared with prior art, the present invention has the following advantages and beneficial effect:

The printing net-point crown structure spectrum CSS that the present invention extracts is how much lattice point structure features under small spatial scale; Its technology path can be realized direct-detection and the analysis to print quality with enforcement; Simultaneously it is as a quality index, can combine with the geometrical characteristic parameter (dot shape, site size, screen frequency, screen angle) of site bunch, and typography is controlled and evaluation.

The invention solves at present take site bunch the problem that the site geometrical characteristic parameter that is extracted for basis is not enough to describe the fine-feature of actual print site edge roughness, for the product quality detection that realizes the site level and analysis and print production control provide technological means.

The accompanying drawing explanation

Fig. 1 is process flow diagram of the present invention.

Fig. 2 is halftone dot image pretreating effect figure: (a) the original site Dot of input _Org(b) the site Dot that obtains after greyscale transformation and binary transform _Bin(c) strengthen the site Dot that obtains after processing _Enh.

Fig. 3 is the edge-central area figure Edg-CA of site.

Fig. 4 is the design sketch of circular shaped lattice point Hough conversion process: the site central point CP that (a) extracts and edge Edg signature; (b) Dot _EnhEdge, site and reconstruction site Dot _RecThe edge labelling figure at edge.In figure, central point is horizontal white line and the intersection point of vertical white line.

Fig. 5 is site crown structure and the crown structure spectrogram that extracts: (a) site crown structure C S figure; (b) the site crown structural drawing that launches; (c) site crown structure spectrum CSS figure.In figure (b-c), horizontal ordinate is the sequence number of crown structure envelope coboundary pixel, and ordinate is distance and the Dot of each pixel of crown structure envelope coboundary apart from the center, site _RecThe difference of radius r.

Embodiment

Below in conjunction with accompanying drawing, and the present invention will be described as example take the edge roughness feature extraction of the shaftless printing net-point of circle.Whole implementation is carried out according to appended Fig. 1 institute draft scheme.

From print sample, choose and input and obtain original halftone dot image Dot _Org, as shown in appended Fig. 2 (a).For shaftless site, select the site in the 30%-40% scope to become number to be advisable; Conventional greyscale transformation and binary transform processing are carried out in the input site, and output is as shown in appended Fig. 2 (b).

For eliminating around site the picture structure noise that is formed by the cavity that flies China ink and hollow etc., project organization unit carries out the enhancing processing of mathematical morphology opening and closing operation filtering to the two-value halftone dot image, obtain halftone dot image Dot _Enh.Wherein, structural elements is 3 * 3 pixels, to obtain the simply connected region halftone dot image as the interative computation end condition.Halftone dot image through strengthening processing is as shown in appended Fig. 2 (c).

With single pixel structure unit to site binary map Dot _EnhCarry out the erosion filter processing, and by figure as a result and the Dot of filtering processing _EnhCarry out difference processing, obtain the edge Edg of site.

Utilize Dot _EnhAnd Edg, add up respectively the area and perimeter of site binary map and calculate girth square-Area Ratio.On mathematics, circular and square girth square-Area Ratio is respectively 12.57 and 16, and selective value 14.3 is the judgement threshold limit value (TLV).Site Dot shown in accompanying drawing 2 _EnhGirth square-Area Ratio is 12.79, so the form parameter SP that can obtain site is for circular.

Circular configuration unit with 3 * 3 pixels carries out the iteration erosion filter to Dot2, obtains the central area CA of site; The edge of output site-central area figure, as shown in Figure 3.

According to the thought of Hough conversion, be directed to the ballot device that circular shaftless net-pont design comprises 5 tuple data structures of centre coordinate, radius, counter and travel through respectively EdgHe site, edge, site central area CA, vote.By the maximum statistical value output center CP coordinate of ballot device Counter, and the numerical value of radius r, the site central point that extracts and sideline mark are as accompanying drawing 4(a) as shown in.According to this centre coordinate and radius, site is rebuild, obtain site Dot _Rec, as accompanying drawing 4(b) as shown in.

To site Dot _EnhWith site Dot _RecCarry out XOR, remove both common factors, keep the actual print site and rebuild the difference region between site, thereby extract, obtain site crown structure C S, result is as accompanying drawing 5(a) as shown in.

Site geometric center point CP and the radius r of utilizing the Hough conversion to extract, carry out spatial alternation to the site crown structure C S that extracts, and obtains the site crown structure of expansion, as accompanying drawing 5(b) as shown in.

The site crown structure of launching is successively calculated and horizontal pixel distance along the pixel on its envelope, is obtained the crown structure spectrum CSS of site, be shaftless printing net-point geometry feature, as accompanying drawing 5(c) as shown in.The statistics parameters such as the average that CSS distributes, variance are that the reference position of launching with site crown structure is irrelevant.

Above case study on implementation only, for explanation technological thought of the present invention, can not limit protection scope of the present invention with this, every technological thought that proposes according to the present invention, and any change of doing on the technical scheme basis, all in protection domain of the present invention.

Claims

1. method that realizes the feature extraction of shaftless printing net-point edge roughness is characterized in that: comprises the following steps,

Step 3, to strengthening site Dot _EnhExtract central area CA;

Step 4, the above extracted edge Edg, central area CA of foundation and dot shape feature Shp, extract and strengthen site Dot by the Hough conversion _EnhGeometric center parameters C P and form parameter SP;

Step 5, utilize above extracted dot shape parameter S P and geometric center parameters C P to rebuild site, obtain rebuilding site Dot _Rec

Step 7, utilize above extracted geometric center point CP, dot shape parameter S P and site crown structure C S, obtain the crown structure spectrum CSS of site, obtain shaftless printing net-point edge roughness feature.

2. a kind of method that realizes the feature extraction of shaftless printing net-point edge roughness as described in claim 1, it is characterized in that: it is the opening and closing operation realization by mathematical morphology that the enhancing in described step 1 is processed, and to obtain the simply connected region halftone dot image as mathematical morphology interative computation end condition, the final lattice point structure noise that causes by flying China ink, cavity of removing.

3. a kind of method that realizes the feature extraction of shaftless printing net-point edge roughness as described in claim 1, is characterized in that: in described step 2, strengthen site Dot _EnhThe leaching process of edge Edg is: first by single dot structure unit, it is carried out to the resulting corrosion of mathematical morphology erosion operation site Dot _E, then carry out Dot _EnhWith Dot _EImage difference.

4. a kind of method that realizes the feature extraction of shaftless printing net-point edge roughness as described in claim 1, it is characterized in that: in described step 2, resolving of dot shape feature Shp is by statistics Dot _EnhThe pixel count at edge and Dot _EnhThe pixel count of itself, obtain corresponding perimeter L and area S, and with L ²With the ratio of S, differentiate dot shape feature Shp: as (L ²/ S) value was near 16 o'clock, and Shp is square; As (L ²/ when S) value was near 4 π, Shp was circular.

5. a kind of extracting method of realizing shaftless printing net-point edge roughness feature as described in claim 1, is characterized in that: Dot in described step 3 _EnhThe extraction of central area CA is to carry out the realization of iteration erosion operation by the consistent structural elements of dot shape feature Shp of resolving with step 2.

6. a kind of extracting method of realizing shaftless printing net-point edge roughness feature as described in claim 1, it is characterized in that: the dot shape feature Shp that described step 4 need to be resolved for step 2, adopt respectively two kinds of different Hough realization that varies one's tactics, be respectively:

(1) for circular shaped lattice point, set up the 5 tuple data structures that comprise central coordinate of circle, radius, counter and vote, according to voting results output geometric center parameters C P and the form parameter SP of its Counter, this moment, SP was radius value r;

(2) for square site, set up two tuples comprise slope, intercept and votes according to structure, according to the voting results front two groups of slopes of output and 4 values of intercept of counter, by two groups of slopes wherein, calculated two slope value of square site; Further obtain form parameter SP and geometric center parameters C P, this moment, SP was length of side value a.

7. a kind of extracting method of realizing shaftless printing net-point edge roughness feature as described in claim 1, it is characterized in that: described step 7 middle coroan structure spectrum CSS is by distance and the Dot of each edge pixel on crown structure C S envelope apart from site center C P _RecThe difference of radius calculates.