CN104614384B - Quality detecting method of printing product character - Google Patents
Quality detecting method of printing product character Download PDFInfo
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- CN104614384B CN104614384B CN201510065317.8A CN201510065317A CN104614384B CN 104614384 B CN104614384 B CN 104614384B CN 201510065317 A CN201510065317 A CN 201510065317A CN 104614384 B CN104614384 B CN 104614384B
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Abstract
The invention relates to a printing quality detecting method of a printing product character, and belongs to the technical field of printing. The printing detecting method comprises the following steps: performing printing output by using a vector character and a dual-dot icon loaded above the character as a digital origination to obtain a detection pattern; performing resolving power calibration and optical reflectivity calibration by adopting a digital imaging system; converting the detection pattern of a printing product character into an RGB digital image with high resolution by using the digital imaging system; obtaining an optical reflectivity gray scale image by virtue of a calibration relation; performing orientation correction; converting the resolution of the corrected character gray level image into a resolution of the digital origination, and extracting a character region in a sample image according to an extracting manner of the digital origination; and comparing with pixels in the same positions of the image of the character region of the digital origination and performing processing analysis to obtain a character quality index value. A printing product character quality index established by the printing quality detecting method is capable of characterizing characteristics of darkness, deformation and skip printing of character strokes, and can be used for quality characterization and control of layout and printing product characters in conventional and digital printing.
Description
Technical field
The present invention relates to a kind of quality determining method of printing word, belongs to printing technology.
Background technology
Leaflet is indispensable in daily life, such as books, package etc..For any printing, word
All it is important content, especially for printings such as books, newpapers and periodicals, and descriptions of commodity, the printing quality of word is particularly important.
But in current print quality detection, only the printing quality of different font size words is passed judgment on by visually-perceptible, still do not measured
The index of change.
In referential correlation technique, international standard ISO/IEC 13660 and ISO/IEC TS 24790, for printing
With the office equipment hard copy achromatic color forming monochrome image quality of the output in white substrate such as duplicate, to lines, large area on the spot
Color, and the image quality of the printing such as background noise carried out index definition, can be used for the visitor of the field hard copy image quality
Observed quantity and evaluation.Wherein, for character literal, in addition to associated line quality attribute, also define and reflect its pen
The index " filling " of the defect that is contained within biting is drawn, that is, the area bitten accounts for the area ratio of overall stroke.But this definition, for pen
Darkness, the stroke trace drawn it occur frequently that " expansion " or edge " incompleteness " etc., do not provide assessment indicator.Additionally, Chinese Character
Volume morphing is abundant, stroke is complicated and simple various, and identical printing condition, print quality also have very big difference.Such as, identical font size
Easily there is the phenomenon that stroke broadens in word, the relatively most wide black matrix of stroke, and the Song typeface of relative narrower, then easily there is stroke
Incomplete phenomenon.The darkness of different in width stroke word is also significantly different.These phenomenons are in such as blocking product, medical product explanation
Book etc. is more easy in the printing using small type size word to be occurred.
Therefore, it is possible to be directed to the morphological characteristic of Chinese character, directly give word darkness and stroke defect characteristic etc. and relatively believe comprehensively
The quantitatively evaluating of breath, the quality characterization of printing product word is very necessary.
The content of the invention
The purpose of the present invention is to set up a kind of print quality inspection method of printing word, including printing plate and final printing
Product.By obtain printing on word digitized video and utilize image analysis technology, the word is compared with its Digital Manuscript
To obtaining the printing quality of word.
A kind of quality determining method of printing word, comprises the following steps：
(1) the double dot charts loaded with vectorial characters and above word are denoted as Digital Manuscript, and Digital Manuscript is changed
For * .GIF or * .bmp images, print output and obtain detecting pattern；
(2) using the digital imaging system of high resolution, enter line definition to the imaging system and demarcate and luminous reflectance school
It is accurate；
(3) by digital imaging system, printing text detection pattern is converted into into high-resolution RGB digitized videos；
(4) the RGB digitized videos obtained to step (3), by the calibration relation of step (2), obtain luminous reflectance gray scale shadow
Picture；
(5) grayscale image obtained to step (4), carries out directional correction；
(6) after the correction for obtaining step (5), the resolution conversion of word grayscale image is the resolution of its Digital Manuscript,
And by the extracting mode of Digital Manuscript, extract the character area in the sample image；
(7) the word sample image obtained by step (6), by the same position picture with its Digital Manuscript image character region
Element compares and analyzes, and obtains text quality desired value.
In step (1), vectorial characters pattern is made in software for composing, and double round dot icons, number are loaded above word
Word original copy is * .ai forms, and word icon design packet includes dark-coloured and light tone word；Afterwards, word vector pattern is converted to suitably
High-resolution * .GIF or * .bmp images, print output obtain detect pattern；Finally, the basis in high-resolution word image
Double dot charts are demarcated position and take out the only region comprising word, are detection character area image.
The Digital Manuscript of printing word used is the representational word of font size to be paid close attention to and font.Font size of interest
To need to apply or to the representational font size of printing quality in specific printing mode, such as 4 pounds；Representational font need to select energy
The conventional character feature of Chinese character, the such as Song typeface or black matrix are represented enough；Representational word need to be containing the different directions such as horizontal, vertical, oblique
Stroke.
Double dot charts above word are designated as separate two of horizontal direction with big dot, and the two round dot centers of circle are in same water
On horizontal line, distance of separation is slightly larger than character area width to be tested.
In step (2), the resolving power of digitized video imaging system must meet the requirement of analysis precision, i.e., must can guarantee that and be intended to point
The most thin stroke width of analysis can use several imaging pixels to represent.
For the CCD digital imaging systems being made up of optical amplifier and CCD imager part, CCD imager part to it is used into
As white light source is adjusted to white balance, from certain enlargement ratio, under the conditions of the micro-imaging selected, to the imaging system
Enter line definition to demarcate and luminous reflectance calibration.
The method demarcated to CCD imaging systems resolving power, comprises the steps：
1) double round dot scale icons are shot by CCD imager part, forms scale map target digitized video；Double round dot scale maps
Mark includes that two diameter identical round dots, the diameter of round dot and two round dot distance of center circle can be designed as needed and adjust.
2) calculated under the image-forming condition by the corresponding pixel count of two round dot distance of center circle in double round dot scale icon digitized videos
The resolving power of digitized video.
Wherein, the actual resolving power selected should be determined according to the font size to be detected.Such as examine for the word of 4 pounds of sizes
Survey, system institute is into no more than 2 μm of dimension on each pixel correspondence imaging object plane of digitized video.
The method calibrated to the luminous reflectance of CCD digital imaging systems, comprises the steps：
1) print the colour table of the several color lump compositions for changing from shallow to deep；Described colour table includes no less than 15
The color lump of different dot area percentages, each color lump are shaped as square, and the length of side is not less than 10mm.Such as dot area percentage value from
Uniform value between 0%～100%, chooses the color lump of more than 15 different dot area percentages as Digital Manuscript, with manuscript
Identical is printed output under the conditions of printing and obtains colour table.
2) measure and calculate the luminous reflectance ρ of each color lump of colour table；
To printing plate situation, by the spectral reflectivity of each color lump of spectrophotometer measurement colour table, further according to the face of plate imaging
Color characteristic, chooses a suitable wave-length coverage in its complementary color optical band, and such as aeruginouss, the light of different ink amount color lumps is anti-
The rate difference of penetrating occurs mainly in its complementary color light-red spectral band, then selectable wave-length coverage is between 600nm～700nm.It
Afterwards, ask for respectively each color lump spectral reflectivity in selected wave-length coverage and with standard white version spectral reflectivity and ratio, be
The luminous reflectance ρ of each color lump.
Printing product situation, then it is by (optics) density D of each color lump of spectrophotometer measurement colour table, further close by (optics)
Definition (1) formula of degree calculates luminous reflectance ρ.It is as follows：
D=-log10ρ (1)
ρ=10-D (2)
3) by CCD imaging systems to colour table colors block imaging, to the meansigma methodss that RGB is responded are asked in the middle part of digital picture,
Change maximum color value, and normalization with different color blocks in choosing rgb value, be designated as d；
4) ρ the and d values according to all color lumps of colour table, set up mathematical relationship between the two, i.e., the CCD shadows under the image formation state
As the calibration relation between response value and printing luminous reflectance.
In step (3), printing text detection pattern is shot into into high-resolution RGB digitized videos；Image-forming condition used
It is same as step (2).The RGB digitized videos of captured printing word, need to save as * .GIF or * .bmp forms.During shooting, on word
Double round dots of side will be substantially in same horizontal line, and two circle center line connectings are not more than 2 degree with horizontal line deviation angle.
In step (5), described directional correction is double round dot regions that top is automatically taken out using adaptive method, and
The central coordinate of circle of double round dots is solved, according to the two central coordinate of circle rotary sample image to the two round dot centers of circle in same horizontal line
On.
In step (6), the resolution conversion of the image is will to set up in the resolution match of sample image to step (1)
Alphanumeric master copy image, that is, reach and alphanumeric original copy identical pixel-physical size corresponding relation.Using method
A zoom factor k is to determine, the sample image after the directional correction that step (5) is obtained is zoomed in or out with the zoom factor.
Zoom factor k is two round dot distance of center circle of sample image after the distance of center circle and directional correction of two round dots in alphanumeric master copy image
Ratio.
With the upper left corner center of circle as round dot, when being extracted with alphanumeric original copy, identical positions and dimensions extract sample image
In character area, formed with Digital Manuscript character area image targeted by can with position pixel ratio compared with sample image.
In step (7), the quality index of printing word include word luminous reflectance, the broken string number of character stroke, broken string and
Empty number and cyst areas ratio in incomplete gross area ratio, expansion area ratio, stroke.
Each index is defined as follows：
1) word luminous reflectance or density
For the average luminous reflectance in character stroke or (optics) density, the darkness of word is represented.
2) the broken string number of character stroke
It is printing stroke compared with the standard stroke of alphanumeric original copy, the stroke open position number of appearance, reflection one
Plant incomplete defect.
3) broken string and incomplete gross area ratio
It is that, compared with the standard stroke of alphanumeric original copy, the stroke area lacked at broken string and stroke edge accounts for standard
The percentage ratio of stroke area, reflects the deficiency of text printout inking amount.
4) expand area ratio
The percentage ratio of standard stroke area is accounted for for the area that stroke extends away, reflects what printing ink quantity was sprawled on base material
Affect.
5) empty number in stroke
The empty number of the independence to be formed of biting for stroke endogenous cause of ill.
6) cyst areas ratio in stroke
The percentage ratio of standard stroke area, reflection printing bite journey of the inking on base material are accounted for for cyst areas in stroke
Degree.
Equally applicable for base material inking, the word formed by non-inking (referred to as " leakage is white "), above-mentioned definition, only inking contains
It is adopted contrary.
The method for solving of each quality index is as follows：
(1) a gray threshold is set, extracts the stroke area of word；For the stroke area that each is closed, remove
There is no the noise region of common ground with corresponding alphanumeric master copy image character area, retain the trace for belonging to character stroke
Region.
(2) for belonging to the region of character stroke in sample image, luminous reflectance (gray value) meansigma methodss are asked for, as text
The luminous reflectance of word；For final printing word situation, further according to the relation of luminous reflectance ρ and (optics) density D, i.e.,
(1) formula relation D=-log10ρ obtains (optics) density D of word.
(3) the sample grayscale image for only being retained character area is converted to two-value image, and character area part value is 1,
Remainder value is 0 (identical with alphanumeric master copy image).
(4) belong to the closed area number of word segment in asking for sample image, it is due that the number deducts word used
Place's number of closed area number, as word broken string.
(5) difference of alphanumeric original copy and sample word two-value image is asked for, difference is that 1 part is sample word pen
Incomplete part is drawn, sum that is all 1 values and being worth divided by original copy for type composition stroke all 1 obtains breaking and the incomplete gross area
Than.
(6) difference of sample word two-value image and alphanumeric original copy is asked for, difference is that 1 part is sample word pen
Draw the part of expansion, sum that is all 1 values and being worth divided by original copy for type composition stroke all 1, the gross area ratio for as expanding；And difference
Part for -1 is the hollow sectors in word trace stroke, and its closed area number is empty number, owns the absolute of -1 value sums
It is worth the sum divided by all 1 values of alphanumeric original copy stroke, that is, obtains cyst areas ratio in stroke.
The word and double round dot identification images of present invention design font size of interest and font, respectively constitute printing file and
Detection image file.Printing word pattern to exporting carries out micro- amplification and CCD imagings, and imaging system is carried out by image
It is worth the calibration of printing ink marks luminous reflectance, and printing word image is changed into luminous reflectance grayscale image with this.Using image
In double round dot centers of circle positioning function, be consistent with original copy for type composition by printing word grayscale image directional correction；Further, convert
Its resolution is identical with original copy for type composition, and extracts identical character area.By printing image and master copy image phase identical text
The respective pixel in block domain compares, and realizes that the quality index of printing word is solved.The printing text quality index set up can
Characterize the darkness of character stroke, deform and bite etc. feature, can be used for the matter of the traditional and digital printed middle space of a whole page and printing word
Scale is levied and control.
The present invention reflects word trace with the deformation behaviour of the digital image response value and character stroke of word trace respectively
Light reflection and quality morphology.Quality index includes the darkness feature of word, and the number of drawbacks feature of character stroke, can
The visual quality of printing word is comprehensively characterized more.
Description of the drawings
Flow charts of the Fig. 1 for detection method.
Fig. 2 (a) to Fig. 2 (f) word pattern master copy images used by the embodiment of the present invention；Wherein, Fig. 2 (a) and Fig. 2 (b)
For dark word pattern original copy；Fig. 2 (c) and Fig. 2 (d) are bright word pattern original copy；Fig. 2 (e) and Fig. 2 (f) are detection character area shadow
Picture.
Fig. 3 is double round dot icons of different distance of center circle used by the embodiment of the present invention.
Fig. 4 (a) and Fig. 4 (b) imaging system calibration colour table images used by the embodiment of the present invention；Wherein, Fig. 4 (a) is
To plate imaging calibration colour table；Fig. 4 (b) is the black trace imaging calibration colour table to paper printing products.
Fig. 5 (a) and Fig. 5 (b) is respectively the printing plate dead color word pattern image of embodiment of the present invention printout, Fig. 5 (c)
The printing plate light colour word pattern image of embodiment of the present invention printout is respectively with Fig. 5 (d).
Fig. 6 (a) and Fig. 6 (b) is respectively embodiment of the present invention paper printing products black letters dead color word pattern image, Fig. 6
C () and Fig. 6 (d) are respectively embodiment of the present invention paper printing products black letters light colour word pattern image.
Fig. 7 is double round dot icon area extraction method schematic diagrams used by the embodiment of the present invention.
For the double round dot centers of circle of the embodiment of the present invention, Fig. 8 (a) and Fig. 8 (b) determines that result illustrates image.
Fig. 9 (a) and Fig. 9 (b) is detected the character area signal image that pattern is extracted for the embodiment of the present invention；Wherein,
Fig. 9 (a) is character area luminous reflectance grayscale image；Two-value images of the Fig. 9 (b) for character area.
Figure 10 is that the qualitative character after the tested printing word of the embodiment of the present invention is aligned with original copy word illustrates image.
Figure 11 (a) to Figure 11 (c) is the embodiment of the present invention to printing plate and two kinds of paper printing products text quality testing result figures；
Wherein, Figure 11 (a) is character stroke average light reflectivity results；Figure 11 (b) compares result for character stroke incompleteness area；Figure 11
C () compares result for character stroke expansion area.
Specific embodiment
The present invention is further illustrated below in conjunction with drawings and Examples, but can not be used for limiting the scope of the present invention.
As shown in figure 1, for the flow process of detection method, including word pattern original copy make and print, pattern it is aobvious
Micro- amplification and CCD imagings, carry out yardstick demarcation and calibration, image reflectivity conversion, image direction correction, word to CCD imagings
Strokes extraction and quality index are solved.
Following examples are printing plate prepared by a kind of inkjet printing, and the black letters print being printed onto on two kinds of paper
Product.And the embodiment pays close attention to the word of 4 pounds of sizes, i.e., detected for the trace of 4 pounds of words.The following detailed description of detecting
Journey.
Detecting system used includes hardware and software two parts.Hardware includes micro- magnifying optics, CCD colour imagings
Device and computer；Software is by the image acquisition developed and the calculating instrument of each quality index.
Wherein, microscope used is Chongqing Austria spy SZ66-TR, continuously adjusts function, object lens with enlargement ratio and focal length
Enlargement ratio from 0.68 times to 4.5 times continuously adjustabe, the enlargement ratio of eyepiece is 10, and total enlargement ratio is 6.8 times to 45 times.
Microscope imaging terminates CCD imager part, and brand and model is COOLSNAP3.3M, with 2048 × 1536 CCD units, i.e. shape
Into digitized video have 2048 × 1536 pixels.CCD imager part is connected with computer, is imaged by computer controls.It is aobvious
Micro mirror object space end is fixed with D65 annular white light sources, irradiation it is lower can the movement of x, y direction object disposing platform.Detected sample
Pattern is placed on articles holding table, is gathered by CCD and form RGB digitized videos after micro-imaging, computer software to image at
Reason realizes detection.
Detection process is as follows：
1st, made comprising 4 pounds of Song typefaces and 4 pounds of black matrix words " sub- v " and double dot charts respectively in Illustrate softwares
Target two-value vectorial characters pattern.Wherein, above word, the size of two horizontal positioned round dots is identical, a diameter of 0.5mm, interval
For 2.4mm, such as Fig. 2 (a), Fig. 2 (b) are shown.The original copy saves as * .ai forms, keeps the vectorial property of image.
Word vector pattern is converted to into suitable high-resolution * .GIF or * .bmp images, printing obtains dead color and light tone
Word pattern.Fig. 2 (a) and Fig. 2 (b) is respectively the dark-coloured word of 4 pounds of Song typefaces and black matrix, and dark-coloured word segment will be by off-set oil
Ink or marking ink are constituted；Will be two images anti-phase, as a result as shown in Fig. 2 (c) and Fig. 2 (d), the respectively 4 pounds Song typefaces and black
The light tone word of body, dark-coloured background parts will be made up of ink or marking ink, and word segment will be by substrate surface color structure
Into such as paper surface.
The word icon is designed with dark-coloured and light tone word, is considered in addition to books and periodicals class printing mainly uses dark-coloured word,
Often by paper substrate color presentation word is exposed on dark background in packaging printing, with aobvious noble quality.Both words are all detection
Content, can reflect the adaptability of two kinds of different applications of printing.
The Song typeface and black matrix is selected to be because, black matrix is that stroke is most wide in Chinese character, and the same width of horizontal, vertical stroke, and the Song typeface
Horizontal, vertical stroke it is narrower, and horizontal, vertical stroke width difference is maximum, and the Song typeface and black matrix are also two kinds of conventional fonts in Chinese character,
Thus it is most representative.
" son " and " v " two characters are selected, in allowing for word there be horizontal, vertical, oblique stroke, and stroke is simple, Neng Gouti
The disappearance and expansion characteristics of existing stroke.
In the embodiment, printing plate is made first in the way of inkjet printing, print resolution is 1200dpi.Afterwards, then make
With the printing plate in printed on paper.For this purpose, above-mentioned word icon file need to be converted to the pdf document of 1200dpi for printing plate-making.
Meanwhile, it is that text quality detection is used, the word icon file is also converted to the bi-level digital image of 15000dpi, * is saved as
.GIF form.Now, a diameter of 295 pixels of round dot, two distance of center circle are 1417 pixels.
Afterwards, with Fig. 2 (a), Fig. 2 (b) upper left corners round dot center of circle as origin, one determines that position is intercepted comprising text to the right
The region of 1151 pixel × 715 pixels about 1.95mm × 1.21mm sizes of word, formation comprise only the image part of word, and instead
Phase transformation is that the two-value image that stroke and background area shown in Fig. 2 (e), Fig. 2 (f) are represented by 1 and 0 value respectively is standby, is referred to as examined
Character area image is used in survey.
The resolution of detection character area image is not definitely fixed.15000dpi is designed as in the embodiment, be for
With the similar resolution of detection imaging system sample digitized video that CCD is formed under suitable enlargement ratio.
2nd, digital imaging system have selected a suitable enlargement ratio so that visual field is just accommodated including two round dot icons
Word printing pattern.
Double round dot scale icons of different distance of center circle are as shown in Figure 3.Calibration process is：Ask for two in double round dot scale images
The center of circle pixel coordinate of individual round dot, carries out the directional correction of two circle center line connectings according to two central coordinate of circle, becomes horizontal line, and really
Fixed pixel distance of center circle now；The resolving power of image is characterized by the distance of center circle for designing and the pixel distance of center circle ratio.The embodiment
In, double round dot imagings of C scales are almost full with whole visual field, are easy to using larger pixel distance of center circle value improve resolving power
Computational accuracy.Therefore, from C scales to be imaged object plane yardstick resolving power calibration result be 1.531 μm/px (micron/as
Element).
In the 4 pounds of Song typefaces to be detected and black matrix character stroke, about 34 μm of the horizontal stroke width of the most thin Song typeface, therefore, image
1.531 μm of pixel resolving power ensure that the practical sign precision of 4 pounds of character stroke width.The printing plate word pattern for being formed
Shown in image such as Fig. 5 (a) to Fig. 5 (d).
It is as follows to the calibration process of CCD digital imaging systems：
(1) uniform value between printing or printing 0%～100%, the pros that totally 15 different dot area percentages are formed
Shape color lump images original copy, the length of side of each color lump is 12mm.Shown in the situation of printing plate such as Fig. 4 (a), printed on paper black letters
Situation such as Fig. 4 (b) shown in.Wherein, low haze is base material used or paper color, and most dark color is mass colour on the spot.
(2) printing plate is printed as having used glaucous ink, calibrates the luminous reflectance of different ink amount color lumps on colour table
Main Differences occur in red spectral band.Chosen, in 640nm～700nm, between color lump, the difference of reflectance is relatively large, this
Sample, can be embodied and be characterized the difference of different color blocks ink amount by maximum difference.
By the luminous reflectance or (optics) density of each color lump of spectrophotometer measurement colour table, ρ or D is designated as.Wherein, printing plate feelings
The luminous reflectance ρ of condition be in 640nm～700nm wave-length coverages color lump spectral reflectivity and with standard white version spectral reflectivity
The ratio of sum, and the situation measured value of black printing is vision (optics) density D on paper, then ρ is converted to by (2) formula.Printing plate
Situation selects the wave-length coverage of 640nm～700nm, is because the difference of reflectance sum between printing plate each color lump in the wave-length coverage most
Greatly.
(3) by CCD imaging systems to colour table colors block imaging, and to the average of RGB responses is asked in the middle part of digital picture
Value, chooses R values, is normalized to d；Colour imaging used is encoded for 8, then d=R/255.
(4) ρ the and d values according to all color lumps, are set up the mathematical relationship between ρ and d by one-dimensional approximating method；In the embodiment
The situation of printing plate and black printing employs 3 rank multinomial relations, respectively：
ρ=0.098d3+0.064d2+0.959d+0.000 (3)
ρ=0.459d3-0.115d2+1.094d-0.005 (4)
(3), (4) formula relation be under the image formation state CCD imagings response value respectively with printing plate and printing black ink marks light
Calibration relation between reflectance.
3rd, the word pattern printed is shot, * .GIF forms are saved as.During shooting, it is ensured that the double round dots above word are basic
In same horizontal line, two circle center line connectings are less than 2 degree with horizontal line deviation angle.Fig. 5 (a) show to Fig. 5 (d) and passes through
Word image on 1200dpi inkjet printing printing plates, Fig. 6 (a) to Fig. 6 (d) be then be printed onto with the printing plate it is black on a kind of paper
The image of color word trace.
4th, to printing plate and paper printing products, the R values in image are extracted, respectively by (2) formula and (3) formula relation, by R values
Luminous reflectance is converted to, reflectance grayscale image is formed.
5th, for bright word luminous reflectance grayscale image, the image is deducted with 1 value image of equidimension, and dark word image is then protected
Hold constant, so, the word of two kinds of situations is converted into character stroke and circular segment gray value is less, and background parts gray scale
The larger situation of value.
Hereafter, all row of word image are averaging, and carry out certain smooth, obtain average gray value retinue coordinate
Change curve it is as shown in Figure 7.In Fig. 7, the row coordinate pair of curve answers the position of 90 degree of word image rotate counterclockwise, equivalent to
The row coordinate of former image, luminous reflectance of the vertical coordinate for column average.
In Fig. 7 curves change procedure from left to right, it is the high reflectivity regions on round dot top first, is double round dots afterwards
The average low reflectivity regions for being formed, then to the high reflectivity regions between double round dots and word.Therefore, change from left to right
Cheng Zhong, first luminous reflectance peak position then correspond to double clear areas between round dot and lower section word.So, solve the peak position point
Corresponding curve level coordinate position A, as extracts the row coordinate position in double round dot regions, and 1 row to A image in the ranks is
Double round dot regions.
Double round dot regions are carried out with edge extracting and the center of circle solves.Using method be：It is respectively directed to each single round dot area
Domain carries out edge extracting and binary conversion treatment, then asks the center of circle to round dot region, as a result as shown in Fig. 8 (a) and Fig. 8 (b).
Wherein the threshold value of edge extracting is that background gray levels add 0.1.The ranks coordinate in two centers of circle be respectively (219,
191) and (211,1786).If two centers of circle are adjusted in same horizontal line, can obtain and need to turn clockwise 0.2874 °.
Afterwards, whole word image is rotated by the anglec of rotation, obtain word image of double round dots in same horizontal line, and
Now this pair of round dot central coordinate of circle and distance of center circle can be obtained.
6th, as the resolution of the sample word image that gathers and alphanumeric original copy during test is inconsistent, position can such as be corresponded to
Pixel ratio is put compared with then needing resolution consistent.In the alphanumeric master copy image of design, the distance of center circle of double round dots is known, is
1431 pixel distances, the situation for solving sample word image is 1595, then need sample word image by 1417/1595
Multiple scales sample word image.So, then obtain the corresponded to picture consistent with the same resolution of alphanumeric master copy image, orientation
The sample word image that element compares.
To sample word image now, with the upper left corner round dot center of circle as starting point, original copy for type composition image is taken from containing double
Identical row and column to the right in dot chart target digitized video, and identical row, column scope takes out word segment, such as schemes
Shown in 9 (a).
7th, the image 9 (a) obtained for step 6, deducts one by the average background reflectivity gray value of surrounding mean pixel
Individual threshold value, it is 0 that pattern word image two-value is turned to stroke area for 1, background area, as a result as shown in Fig. 9 (b).The enforcement
In example, printing plate condition threshold is 0.1, and printing black letters condition threshold is 0.15.
Afterwards, Fig. 2 (e) the alphanumeric master copy images for being prepared by Fig. 9 (b) images and step 1, carry out region and compare and together
The difference of pixel and calculating etc., obtain aforementioned every text quality index.By taking one of printing plate word pattern as an example, formed
Character stroke luminous reflectance, incomplete and expansion area compared than as shown in Figure 10.Wherein, light gray areas are original copy for type composition pens
Part is drawn, black and white pixel is compared to the part of the expansion of original copy for type composition stroke and incompleteness respectively.Additionally, the printing character
Inside does not have cavity.
Using above-mentioned test process, to the printing plate and the black printing word on two kinds of paper, test obtains each word
Shown in quality indicator value such as Figure 11 (a)～Figure 11 (c).
From Figure 11 (a), the optical reflection values and size of dark-coloured word trace stroke are relatively found out, for printing plate, Song
The luminous reflectance of body trace stroke is higher than black matrix situation, shows that Song typeface stroke color is shallow, and not as good as black matrix situation, which ties institute's inking amount
Also always the ink of the Song typeface is measured not as good as black matrix situation really to cause the printing stroke on same paper.Indicate different stroke widths
Depth difference between degree printing word.See simultaneously, for the light colour word situation formed by " showing money or valuables one carries unintentionally ", change in value situation is
Contrary, but this result exactly give also the advantage of black matrix word width stroke.Additionally, relatively seeing also between two kinds of paper
Go out, paper affects very big to word trace quality, and paper therein 1 has more preferable word expressive ability.
From Figure 11 (b), the incomplete area ratio value and size of word trace stroke is relatively found out, either dark word is still
Bright word, performance of the incomplete amount of the thinner Song typeface stroke of stroke always compared with black matrix situation to overall word are more unfavorable.And print to paper
Zhang Shang, the incomplete degree of dark word are substantially reduced, and the incomplete degree of bright word is then significantly improved.Should be in printing process ink in paper
Caused by irregularity on is sprawled.Dark word, bright word these intensity of variations it is still closely related with paper.
From Figure 11 (c), the expansion area ratio value and size of word trace stroke is relatively found out, similarly, either secretly
Word or bright word, performance of the thinner Song typeface stroke swell increment of stroke always compared with black matrix situation to overall word are more unfavorable.Print
After on paper, the degrees of expansion of dark word is significantly increased, and the degrees of expansion of bright word is then substantially reduced.In reflecting printing process
Ink sprawls degree on paper.These intensity of variations are also closely related with paper.
On the whole, either on printing plate, or on paper printing products, the incomplete and expansion of stroke is all while existing
, reason is that the irregularity of stroke edge is coarse and fuzzy.But after this defect of printing plate is transferred on paper printing products, dark word
Situation incompleteness degree always reduce, what degrees of expansion always increased；Bright word situation is then contrary.
Above-mentioned Testing index, can be different literals need for exhibition, different printing plates and different paper situation, there is provided the matter of quantization
Amount characterization method, can pass through the accumulation and analysis of achievement data, instruct process optimization and developing material process, it can also be used to produce
Quality control.
Claims (10)
1. a kind of quality determining method of printing word, comprises the following steps：
(1) the double dot charts loaded with vectorial characters and above word are denoted as Digital Manuscript, are printed output and are obtained detection figure
Sample；
(2) enter line definition to demarcate and luminous reflectance calibration to digital imaging system；
(3) by digital imaging system, printing text detection pattern is converted into into high-resolution RGB digitized videos；
(4) to RGB digitized videos, by calibration relation, obtain luminous reflectance grayscale image；
(5) to the grayscale image for obtaining, carry out directional correction；
(6) it is by the resolution that the resolution conversion of word grayscale image after the correction for obtaining is its Digital Manuscript and former by numeral
The extracting mode of original text, extracts the character area in the sample image；
(7) to the word sample image for obtaining, by with the same position pixel ratio of its Digital Manuscript word image compared with process point
Analysis, obtains text quality desired value.
2. the quality determining method of printing word according to claim 1, it is characterised in that：Double dot charts above word
Separate two of horizontal direction are designated as with big dot, in the same horizontal line, distance of separation is more than literal field in the two round dot centers of circle
Field width degree.
3. the quality determining method of printing word according to claim 1, it is characterised in that：Digital imaging system is by light
The CCD digital imaging systems amplified with CCD imager part composition are learned, CCD imager part is adjusted to imaging white light source used
White balance, under the conditions of micro-imaging, enters line definition and demarcates and luminous reflectance calibration to imaging system.
4. the quality determining method of printing word according to claim 1, it is characterised in that：Digital imaging system is CCD
Digital imaging system, the method that digital imaging system resolving power is demarcated comprise the steps：
1) double round dot scale icons are shot by CCD imager part, forms scale map target digitized video；
2) numeral under the image-forming condition is calculated by the corresponding pixel count of two round dot distance of center circle in double round dot scale icon digitized videos
The resolving power of image.
5. the quality determining method of printing word according to claim 1, it is characterised in that：Digital imaging system is CCD
Digital imaging system, the method for the luminous reflectance calibration of digital imaging system comprise the steps：
1) print the colour table of the several color lump compositions for changing from shallow to deep；
2) by spectrophotometer measurement and calculate the luminous reflectance ρ of each color lump of colour table；Wherein, for final printing situation, by
Optical density (OD) D of each color lump of spectrophotometer measurement colour table, calculates luminous reflectance ρ by definition (1) formula of optical density (OD)；Such as
Under：
D=-log10ρ (1)；
ρ=10-D(2)；
3) by CCD imaging systems to colour table colors block imaging, and to the meansigma methodss of RGB responses, choosing are asked in the middle part of digital picture
Change maximum color value, and normalization with different color blocks in taking rgb value, be designated as d；
4) ρ the and d values according to all color lumps of colour table, set up mathematical relationship between the two, i.e., under the image formation state, CCD images ring
Should be worth and the calibration relation between printing luminous reflectance.
6. the quality determining method of printing word according to claim 1, it is characterised in that：RGB digitized videos are * .GIF
Or * .bmp forms, two circle center line connectings and the horizontal line deviation angle of the double round dots above word are not more than 2 degree.
7. the quality determining method of printing word according to claim 1, it is characterised in that：Described directional correction is to adopt
Double round dot regions of top are automatically taken out with adaptive method, and solve the central coordinate of circle of pair round dots, according to two center of circle
Coordinate rotary sample image to the two round dot centers of circle in the same horizontal line.
8. the quality determining method of printing word according to claim 1, it is characterised in that：The resolution of described image
Conversion is to the alphanumeric master copy image set up by the resolution match of sample image.
9. the quality determining method of printing word according to claim 1, it is characterised in that：Described text quality index
Including empty number in word luminous reflectance, the broken string number of character stroke, broken string and incomplete gross area ratio, expansion area ratio, stroke
With cyst areas ratio.
10. the quality determining method of printing word according to claim 9, it is characterised in that：Described text quality refers to
Target preparation method comprises the steps：
(1) gray threshold is set, extracts the stroke area of word；For the stroke area that each is closed, remove and corresponding text
In characters/numerals master copy image, character area does not have the noise region of common ground, and reservation belongs to the trace region of character stroke；
(2) for belonging to the region of character stroke in sample image, luminous reflectance meansigma methodss, as the light reflection of word are asked for
Rate；When final printing, according to (1) formula relation D=-log10ρ obtains optical density (OD) D of word；
(3) the sample grayscale image for only being retained character area is converted to two-value image, and character area part value is 1, remaining
Part value is 0；
(4) belong to the closed area number of word segment in asking for sample image, the number deducts the due closing of word used
Place's number of areal, as word broken string；
(5) ask for the difference of alphanumeric original copy and sample word two-value image, it is residual that difference is that 1 part is sample character stroke
Scarce part, sum that is all 1 values and being worth divided by original copy for type composition stroke all 1, that is, obtain breaking and incomplete gross area ratio；
(6) ask for the difference of sample word two-value image and alphanumeric original copy, it is swollen that difference is that 1 part is sample character stroke
The part for going out, sum that is all 1 values and being worth divided by original copy for type composition stroke all 1, the gross area ratio for as expanding；And difference is -1
Part be hollow sectors in word trace stroke, its closed area number is empty number, and the absolute value of all -1 value sums is removed
With the sum of all 1 values of alphanumeric original copy stroke, that is, obtain cyst areas ratio in stroke.
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| CN106530289B (en) * | 2016-11-03 | 2019-04-30 | 刘国勇 | A kind of coding clarity machine vision detection method based on dot matrix |
| CN108681114A (en) * | 2018-05-17 | 2018-10-19 | 福建师范大学 | A kind of detection device and method of small size LCD character display defects |
| CN108982525A (en) * | 2018-08-23 | 2018-12-11 | 云南省印刷技术研究所 | A kind of analysis and detection method for books and periodicals green fine printing quality |
| CN110021048B (en) * | 2019-03-22 | 2021-04-02 | 杭州电子科技大学上虞科学与工程研究院有限公司 | Ink color evaluation method for newspaper printing |
| CN110501335B (en) * | 2019-08-23 | 2021-10-26 | 北京印刷学院 | Method for detecting and characterizing quality of star mark printing product |
| CN110514675B (en) * | 2019-08-29 | 2020-12-11 | 珠海格力电器股份有限公司 | Intelligent detection method and system for label |
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