Method and circuit for recognition of colors

• US 4,414,635 A
• Filed: 11/24/1981
• Issued: 11/08/1983
• Est. Priority Date: 11/28/1978
• Status: Expired due to Term

• Current Assignee: Heidelberger Druckmaschinen Ag
• Original Assignee: Dr ING Rudolf HELL GmbH
• Inventors: Kuhn, Franz, Jung, Eggert, Knop, Hans-Georg, Sommer, Rudiger, Redecker, Friedrich, Gast, Uwe, Wellendorf, Klaus, Mollgaard, Klaus, Sendtko, Ulrich
• Primary Examiner(s): Smith, Jerry
• Application Number:
  US06/324,615
• Time in Patent Office: 714 Days
• Field of Search: 364/526, 358/75, 358/78, 356/403, 356/405, 356/406, 356/419, 356/425, 250/226
• US Class Current: 382/165
• CPC Class Codes: G01J 2003/466 Coded colour; Recognition of predetermined colour; Determining proximity to predetermined colour
• CPC Class Codes: G01J 3/46 Measurement of colour; Colour measuring devices, e.g. colorimeters measuring colour temperature G01J5/60
• CPC Class Codes: G01J 3/462 Computing operations in or between colour spaces; Colour management systems
• CPC Class Codes: G01J 3/513 having fixed filter-detector pairs
• CPC Class Codes: H04N 1/62 Retouching, i.e. modification of isolated colours only or in isolated picture areas only

Abstract

An apparatus and a method for the recognition of colors on a colored image illuminated with a light source of a known spectrum composition, wherein the intensities of three primary colors are measured opto-electronically as color components, which represent the spatial co-ordinates of the color locations in a color space. Prior to color recognition the color components of at least one characteristic test point in each color or color region, which is to be recognized, are measured and noted. The test color components represent the corresponding test color locations in the color space. An identification symbol is assigned to each color component triplet of the test points and noted too. The plurality of color locations in the color space are associated automatically with identification symbols in dependence their respective positions with respect to a spatially close-by test color location, whereby all color locations associated with the same identification symbol appertains to one color recognition region within the color space. Then the colored image is scanned opto-electronically for actual color recognition and the color components thereby obtained are compared with the color components noted, and in case of correspondence, the corrresponding assigned identification symbol is read out, whereby the color components of the colors are verified regarding their correspondence to one of the defined color recognition regions of the color space.

Claims

1. In a method of preparing for and recognizing colors on a colored image with the aid of a light source of known spectral composition, each color corresponding to a color location in a color space, each color location being defined by a color component triplet representing the spatial coordinates of said color location in said color space, and being spaced from another color location by a spatial distance, said color space including at least one spatial color range being defined by at least one of said color locations,

the steps comprising:

preparatory to color recognition

selecting in said colors of said image a number of test points, each test point having a test point color;

illuminating said image with said light source;

photoelectrically measuring the color component triplets of the selected test point colors;

defining a certain identification symbol for each selected test point color;

assigning the defined identification symbols to the color locations corresponding to respective selected test point colors;

calling up a plurality of said color locations from said color space;

determining for each called-up color location the spatial distance separating said called-up color location from the color location of each selected test point color;

selecting the color location of each test point color having the shortest distance from any of said called-up color locations respectively;

determining the identification symbols corresponding to the color locations of said test point colors having said shortest distances, respectively;

assigning said determined identification symbols to said corresponding called-up color locations, so as to form color recognition ranges around the color locations of the selected test point colors within said color space, all color locations assigned the same identification symbol forming said color recognition ranges corresponding to said color ranges, respectively; and

thereafter performing the color recognition steps of;

photo-electrically scanning said colored image point-by-point and line-by-line so as to obtain the color component triplets corresponding to each color scanned from said image;

calling up the color locations represented by said color component triplets and the identification symbols associated therewith; and

reading out said associated identification symbols, whereby the image colors are identified.

2. In a method as claimed in claim 1, wherein at least two image colors are to be combined into a color range and recognized as a single color, and wherein the selecting step of said test points and said test point colors is further defined by

selecting at least one test point in each of said image colors, which are to be combined to a color range;

and

wherein the step of defining identification symbols is further defined by

defining certain identification symbols for each color range, the colors of which are to be recognized as a single color; and

wherein the assigning step of said identification symbols is futher defined by

assigning to all color locations of the test point colors which are to be combined to a certain color range the identification symbol already assigned to said color range.

3. In a method as claimed in claim 1 or 2, carried out with the aid of memory means having a plurality of storage locations, each storage location representing a color location of said color space, said storage locations being addressable by digital signals representing the color component triplets of said corresponding color locations, and further comprising the steps of:

storing the color locations associated with said identification symbols, respectively;

said color-recognition step of calling-up color locations represented by said color component triplets and the identification symbols associated therewith including the step of recognizing the image colors in terms of said digital signals;

obtaining said digital signals representing said color component triplets from the photo-electrical scanning step,

addressing the storage locations of said memory means by said digital signals obtained during the recognizing step; and

reading out said corresponding identification symbols from said memory means,

said determining, selecting, assigning and readout steps being carried out by digital processing steps, whereby the image colors obtained during the color recognition steps are identified by said digital processing steps.

4. In a method as claimed in claim 1 or 2, wherein some called-up color locations are equidistant from the color locations of several selected test point colors, and wherein some of said identification symbols allotted to said test point colors occur more frequently than others, and further comprising the step of assigning, in the event one of said called-up color locations is equidistant from the color locations of said several selected test point colors, the identification symbol occurring most frequently among said several test point colors allotted to said one called-up color location.

24. In a method as claimed in claims 1 or 5, further utilizing a memory having available a plurality of storage locations, and wherein said image has a limited color content compared to a theoretically available full color content of the color space,

the steps further comprising

subdividing said color space into a plurality of color zones,

digitizing the color component triplets, said color zones being defined by corresponding of said digitized color component triplets,

assigning said plurality of said storage locations to said plurality of color zones, respectively,

a first plurality of digitized color component triplets representing said full color content of the color space, said plurality of storage locations being addressable by said first plurality of the color component triplets,

obtaining a second plurality of digitized color component triplets from said scanning step, so as to represent said limited color content of said image, and matching said second plurality of digitized color component triplets to said first plurality of digitized color component triplets.

25. In a method as claimed in claims 1 or 5, further including at least one photo-electric transducer, and wherein the measuring step includes measuring the color component triplet of each selected test point color by means of said photo-electric transducer.

26. In a method as claimed in claims 1 or 5, further utilizing a color monitor and a cursor, and further comprising the steps of displaying said colored image on said color monitor, and pin-pointing the test points on said image with the aid of said cursor.

27. In a method as claimed in claims 1 or 5, further comprising the steps of digitizing the color component triplets obtained from said colored image at different respective resolutions.

28. In a method as claimed in claims 1 or 5, wherein the color component triplets correspond to the primary color signals of Red, Green, and Blue.

29. In a method as claimed in claims 1 or 5, wherein said color space is a Red, Green and Blue color space, and further comprising the step of coordinate-transforming said Red, Green and Blue color space into a Chrominance/Luminance color space containing chrominance signals (X,Y), and a luminance signal, and wherein said color component triplets correspond to said chrominance signals and to said luminance signal.

30. In a method as claimed in claims 1 or 5, wherein said color space is a Red, Green and Blue color space, and further comprising the step of coordinate-transforming said Red, Green and Blue color space into a Saturation/Hue/Luminance color space containing cylindrical color coordinates, and wherein said color component triplets correspond to said cylindrical color coordinates.

31. In a method as claimed in claim 30, wherein said Saturation, Hue and Luminance color space includes a gray axis, and wherein the color-recognition region forming step includes the step of surrounding said gray axis with said color-recognition region so as to identify a gray color.

32. In a method as claimed in claim 31, further comprising the step of shaping said color-recognition region in the form of a barrel.

33. In a method as claimed in claim 31, further comprising the step of shaping said color recognition region in the shape of a cylinder.

34. In a method as claimed in claim 30, wherein said color-recognition region forming step includes the step of narrowing said color recognition range along the direction of the Hue axis by a coordinate conversion of the color component triplets.

5. In a method for preparing and recognizing colors on a colored image with the aid of a light source of known spectral composition, each color location corresponding to a color location in a color space, said color locations being defined by color component triplets representing the spatial coordinates of said color locations in said color space, said color space including at least one spatial color range being defined by at least one color location,

the steps comprising:

preparatory to color recognition

selecting in said colors of said image a number of test points, each test point having a test point color;

illuminating said image with said light source;

photo-electrically measuring the color component triplets of the selected point colors;

defining a certain identification symbol for each selected test point color;

assigning the defined identification symbols to the color locations corresponding to respective selected test point colors;

surrounding the color location of each test point color with selected color locations so as to form shells of successively increasing size around the color location of the color location of the corresponding test point color,

calling-up said selected color locations shell by shell at successively increasing distances from the color location of the corresponding test point color,

checking each called-up color location to determine whether an identification symbol has already been allotted thereto

assigning the identification symbol allotted to a corresponding selected test point color to said called-up color location, provided no identification symbol has already been allotted to said called-up color location, all color locations bearing the same identification symbol thereby forming a color recognition region around the color locations of each corresponding selected test point color, each color recognition region representing a corresponding color range,

thereafter performing the color recognition steps of;

photo-electrically scanning said colored image so as to obtain the color component triplets corresponding to each image color,

calling-up the color locations represented by said color component triplets and the identification symbols associated therewith, and

reading out said identification symbols, whereby the image colors are identified.

6. In a method as claimed in claim 5, wherein at least two image colors are to be combined to a color range and recognized as a single color, respectively, and wherein the selecting step of said test points and test point colors is further defined by

selecting at least one test point in each of the image colors which are to be combined to a color range;

defining certain identification symbols for each color range, the colors of which are to be recognized as a single color; and

wherein the assigning step of said identification symbols is further defined by

assigning to all color locations of the test point colors which are to be combined to a certain color range the same identification symbol already assigned to said certain color range.

7. In a method as claimed in claims 5 or 6, wherein the color location surrounding step further comprises the step of forming a plurality of first shells around said color locations of said test point colors, and equidistant therefrom, respectively, and thereafter forming other shells of successively increasing size in timely succession.

8. In a method as claimed in claims 5 or 6, wherein the step of calling-up said selected color locations comprises calling-up said color locations successively.

9. In a method as claimed in claim 5 or 6, wherein the color location surrounding step further comprises the step of forming each shell substantially as a sphere.

10. In a method as claimed in claim 5 or 6, wherein the color location surrounding step further comprises the step of forming said shells substantially in the shape of a cube.

11. In a method as claimed in claim 5 or 6, wherein said color space is subdivided into a plurality of color zones representing said color locations, said color zones being defined by digital signals, further comprising the steps of:

generating said digital signals by digitization of said color component triplets, respectively, obtained from the photo-electric scanning step, and

approximating said shells by said digital signals corresponding to said selected color locations, respectively.

12. In a method as claimed in claim 11, further utilizing first, second and third memories, having a plurality of first, second and third storage locations, respectively, and further comprising the steps preparatory to color recognition, of

digitizing the color component triplets,

subdividing said color space into a plurality of color zones,

assigning said plurality of said first storage locations of said first memory to said color zones and to said identification symbols, respectively, said first storage locations being addressable by corresponding digitized color component triplets,

storing the identification symbols associated with each selected test point color in corresponding of said first storage locations of said first memory;

the digitized color component triplets (x_pn, y_pn, z_pn) of the color locations of the test point colors and the identification symbols corresponding thereto constituting a sample list,

storing said sample list in corresponding second storage locations of said second memory,

the spatial coordinates (x_sm, y_sm, z_sm) of the selected color locations forming said shells constituting a shell list,

storing said shell list in corresponding third storage locations of said third memory, calling up the addresses of said second and of said third storage locations,

determining the color component triplet coordinates (x_i, y_i, z_i) of said selected color locations of said shells from said sample list and from said shell list,

addressing said first storage locations by the so determined color component triplet coordinates, and wherein the checking step includes checking each of said addressed first storage locations of said first memory to determine whether an identification symbol has been stored therein, and in the event no identification symbol has been stored in a corresponding of said checked first storage location,

storing the identification symbol associated with the corresponding test point color therein,

and wherein the calling-up step of the color recognition steps includes addressing said first storage locations by the color component triplet coordinates obtained during the scanning step, and the reading out step includes reading out the identification symbols from said first storage locations.

13. In a method as claimed in claims 5 or 6, wherein a representative shell is designated as the m^th shell;

the color locations of said m^th shell having substantially a distance r_m from the corresponding color location of said test point color forming the center of said representative shell, and wherein the spatial coordinates of a selected color location of said m^th shell with respect to said center are x_xm, y_ym, and z_sm, and further comprising the step of deriving said spatial

x_sm, y_sm, and z_xm from the plurality of integers fulfilling the vectorial equation

space="preserve" listing-type="equation">r.sup.2.sub.m =x.sup.2.sub.sm +y.sup.2.sub.sm +z.sup.2.sub.sm.

14. In a method as claimed in claim 13, further comprising the step of determining said spatial coordinates of said selected color locations of said m^th shell by permutation and sign reversal from an ordered co-ordinate triplet fulfilling said vectorial equation

15. In a method as claimed in claims 5 or 6, wherein a representative shell is designated as the m^th shell, the selected color locations of said m^th shell having substantially a distance r_m from the corresponding color location of the test point color, said corresponding color location of said test point color forming the center of said representative shell, and wherein the spatial coordinates of a selected color location of said m^th shell with respect to said center are x_sm, y_sm, and z_sm, the spatial coordinates of a corresponding color location of the test point color being x_pn, x_pn and z_pn, the coordinates of the selected color locations called-up within said m^th shell being the triplet x_i, y_i, and z_i, and further comprising the step of determining said color component triplet coordinates x_i, y_i and z_i in accordance with the vectorial equation

x_i =x_pn +x_sm

y_i =y_pn +y_sm

z_i =z_pn +z_sm.

16. In a method as claimed in claim 15, further utilizing first, second and third memories, having a plurality of first, second and third storage locations, respectively, and further comprising the steps, preparatory to color recognition, of

digitizing the color component triplets,

subdividing said color space into a plurality of color zones,

assigning said plurality of said first storage locations of said first memory to said color zones and to said identification symbols, respectively, said first storage locations being addressable by corresponding digitized color component triplets,

storing the identification symbols associated with each selected test point color in corresponding of said first storage locations of said first memory;

the digitized color component triplets (x_pn, y_pn, z_pn) of the color locations of the test point colors and the identification symbols corresponding thereto constituting a sample list,

storing said sample list in corresponding second storage locations of said second memory,

the spatial coordinates (x_sm, y_sm, z_sm) of the selected color locations forming said shells constituting a shell list,

storing said shell list in corresponding third storage locations of said third memory, calling up the addresses of said second and of said third storage locations,

determining the color component triplet coordinates (x_i, y_i, z_i) of said selected color locations of said shells from said sample list and from said shell list,

addressing said first storage locations by the so determined color component triplet coordinates, and wherein the checking step includes checking each of said addressed first storage locations of said first memory to determine whether an identification symbol has been stored therein, and in the event no identification symbol has been stored in a corresponding of said checked first storage location,

storing the identification symbol associated with the corresponding test point color therein,

and wherein the calling-up step of the color recognition steps includes addressing said first storage locations by the color component triplet coordinates obtained during the scanning step, and the reading out step includes reading out the identification symbols from said first storage locations.

17. In a method as claimed in claims 5 or 6, further comprising the step of terminating the formation of said shells upon one of said increasing distances from the color location of the corresponding test point color reaching a limiting distance.

18. In a method as claimed in claim 17, wherein said limiting distance is predetermined.

19. In a method as claimed in claim 17, wherein said limiting distance depends on the number of test point colors selected.

20. In a method as claimed in claims 5 or 6, wherein the checking step is carried out at a predetermined rate and further comprising the steps of terminating the formation of said shells, if the allotted identification symbols are encountered at a predetermined frequency.

21. In a method as claimed in claims 5 or 6, further comprising the step of terminating the formation of said shells upon shells formed from neighboring color locations of different test point colors making contact with one another.

22. In a method as claimed in claims 5 or 6, further comprising the steps of

terminating the formation of said shells, and the assignment of said identification symbols,

thereafter calling up the color locations still free of any assigned identification symbols,

assigning to each of said color locations still free of any assigned identification symbols the identification symbol corresponding to the color location of the test point color spatially closest to a corresponding of the color locations called-up.

23. In a method as claimed in claim 22, wherein first, second and third memories are utilized, which have a plurality of first, second and third storage locations, respectively, and further comprising the steps, preparatory to color recognition, of

digitizing the color component triplets,

subdividing said color space into a plurality of color zones,

assigning said plurality of said first storage locations of said first memory to said color zones, and to said identification symbols, respectively, said first storage locations being addressable by corresponding digitized color component triplets,

storing the identification symbols associated with each selected test point color in corresponding first storage locations of said first memory,

the digitized color component triplets (x_pn, y_pn, z_pn) of the color locations of the test point colors and the identification symbols corresponding thereto constituting a sample list,

storing said sample list in corresponding second storage locations, of said second memory,

the spatial coordinates (x_sm, y_sm, z_sm) of the selected color locations forming said shells constituting a shell list,

storing said shell list in corresponding third storage locations of said third memory,

calling up the addresses of said second and of said third storage locations,

determining the color component triplet coordinates (x_i, y_i, z_i) of said selected color locations of said shells from said sample list and from said shell list,

addressing said first storage locations by the so determined color component triplet coordinates, and wherein the checking step includes checking each of said addressed first storage locations of said first memory to determine whether an identification symbol has been stored in a corresponding of said checked first storage location,

storing the identification symbol associated with the corresponding color location of the test point color therein, and

following termination of the shell formation, alternately addressing and calling up

said first storage locations still free from having an identification symbol stored therein, and thereafter

said second storage locations,

determining from the addressed and called-up first and second storage locations the color location of a test point color having the smallest spatial distance from each called-up color location, and the identification symbol stored in said second storage location corresponding thereto,

storing each identification symbol corresponding to the color location of the test point color having the smallest spatial distance from each of said called-up color locations in said first storage locations, and wherein the calling-up step of the color recognition steps includes addressing said first storage locations by the color component triplets obtained during the scanning step, and the reading out step includes reading out the identification symbols corresponding to the color component triplets obtained during the scanning step which have addressed said first storage locations, whereby the colors are identified.

35. In an apparatus preparing for, and recognizing colors on a colored image with the aid of a light source of known spectral composition to illuminate said colored image, each image color corresponding to a color location in a color space, said color locations being defined by a color component triplet representing the spatial coordinates of said color locations in said color space, selected image colors being denoted as test point colors and the image colors being identifiable by corresponding color identification symbols,

comprising in combination:

photo-electric transducer means for scanning said colored image and for measuring the color component triplets of the test point colors and of the image colors to be identified,

analog-to-digital converter means postcoupled to said photo-electric transducer means for converting the measured analog component triplets into digitized color component triplets,

color recognition memory means postcoupled to said analog-to-digital converter means, and including a plurality of first storage locations for storing said color identification symbols, said first storage locations being addressable by said digitized color component triplets,

an identification symbol processor connected to said color recognition memory means, and including

an input stage for the assignment of the identification symbols to the test point colors, respectively,

a sample list being defined by the digitized color component triplets associated with the color locations of said test point colors, and the identification symbols assigned to the color locations of said test point colors, respectively,

test point color memory means connected to said analog-to-digital converter means and to said input stage, and including a plurality of second storage locations for storing said sample list,

address-control means connected to said color recognition memory means and to said test point color memory means for selecting addresses of said test point color memory means and of said color recognition memory means, and for calling up chosen color locations represented by said digitized color component triplets, and

processing means connected to said test point color memory means, to said address control means, and to said color recognition means for determining the spatial distances separating called-up color locations represented by said called-up digitized color component triplets from said color locations of said test point colors represented by color component triplets contained in said sample list, respectively, and for determining the identification symbols to be assigned to the called-up digitized color component triplets, the so determined identification symbols being storable in said color recognition memory means and being capable of being called up therefrom.

38. An apparatus as claimed in claims 35, 36 or 37, wherein said color component triplets represent the primary colors Red, Green and Blue, and wherein said photo-electric transducer means generate corresponding primary color signals, and further comprising first color coordinate transformation means postcoupled to said photo-electric transducer means for converting said primary color signals into chrominance signals and into a luminance signal.

39. An apparatus as claimed in claims 35, 36 or 37, wherein said color component triplets representing the primary colors are Red, Green and Blue, and wherein said photo-electric transducer means generate corresponding primary color signals, and further comprising first color coordinate transformation means postcoupled to said photo-electric transducer means for converting said primary color signals into chrominance signals and a luminance signal, and second color coordinate transformation means postcoupled to said first color coordinate transformation means for converting said chrominance signals and said luminance signal into a saturation signal, a hue signal, and a brightness signal.

36. An apparatus for recognizing colors on a colored image with the aid of a light source of known spectral composition to illuminate said colored image, each image color corresponding to a color location in a color space, said color locations being defined by a color component triplet representing the spatial coordinates of said color locations in said color space, selected image colors being denoted as test point colors and the image colors being identifiable by corresponding color identification symbols,

comprising in combination:

photo-electric transducer means for scanning said colored image and for measuring the color component triplets of the test point colors and of the image colors to be identified,

analog-to-digital converter means postcoupled to said photo-electric transducer means for converting the measured analog component triplets into digitized color component triplets,

color recognition memory means postcoupled to said analog-to-digital converter means, and including a plurality of first storage locations for storing said color identification symbols, said first storage locations being addressable by said digitized color component triplets, and

an identification symbol processor connected to said color recognition memory means, including

an input stage for the assignment of the identification symbols to the test point colors, respectively, a sample list being defined by the digitized color component triplets associated with the color locations of said test point colors and the identification symbols assigned to the color locations of said test point colors, respectively,

test point color memory means connected to said analog-to-digital converter means and to said input stage, and including a plurality of second storage locations for storing said sample list,

a shell being defined by surrounding the color location of each test point with selected color locations so as to form a multiplicity of shells of successively increasing size around the corresponding test point color, each shell having a plurality of shell coordinates, the shell coordinates of all shells defining a shell list,

shell memory means including a plurality of third storage locations for storing said shell list,

address-control means connected to said test point color memory means and to said shell memory means for addressing said test point color memory means and said shell memory means,

processing means connected to said test point color memory means, to said shell memory means and to said color recognition memory means for determining selected addresses from said sample list and from said shell list for addressing said color recognition memory means by said selected addresses, and for determining the identification symbols to be assigned to the called-up addresses of said color recognition memory means, and

switching means for checking whether said first storage locations of said color recognition memory means are free from any identification symbols already stored therein.

37. An apparatus as claimed in claim 36, wherein said address-control means are further connected to said color recognition memory means for addressing said color recognition memory means, and for calling up chosen color locations represented by digitized color component triplets, and wherein said processing means are additionally arranged to terminate the formation of said shells, and to subsequently call up the storage locations of the color recognition memory means free of any identification symbol stored therein, and to store in each of the subsequently called-up storage locations the identification symbol assigned to the color location of the test point color spatially nearest to the color location corresponding to said called-up storage location.