WO2002033957A1 - Preservation des couleurs grises - Google Patents

Preservation des couleurs grises Download PDF

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Publication number
WO2002033957A1
WO2002033957A1 PCT/US2000/041337 US0041337W WO0233957A1 WO 2002033957 A1 WO2002033957 A1 WO 2002033957A1 US 0041337 W US0041337 W US 0041337W WO 0233957 A1 WO0233957 A1 WO 0233957A1
Authority
WO
WIPO (PCT)
Prior art keywords
objects
color
colors
gray
color space
Prior art date
Application number
PCT/US2000/041337
Other languages
English (en)
Inventor
Manish S. Kulkarni
Original Assignee
Adobe Systems Incorporated
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Adobe Systems Incorporated filed Critical Adobe Systems Incorporated
Priority to PCT/US2000/041337 priority Critical patent/WO2002033957A1/fr
Priority to US10/168,057 priority patent/US6930690B1/en
Publication of WO2002033957A1 publication Critical patent/WO2002033957A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/56—Processing of colour picture signals
    • H04N1/60—Colour correction or control
    • H04N1/6072—Colour correction or control adapting to different types of images, e.g. characters, graphs, black and white image portions
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/56—Processing of colour picture signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/56—Processing of colour picture signals
    • H04N1/60—Colour correction or control
    • H04N1/62—Retouching, i.e. modification of isolated colours only or in isolated picture areas only

Definitions

  • This invention relates to a method and apparatus for preserving neutral or gray colors attributed to certain types of objects within a document, such as text objects.
  • ком ⁇ онент creates and combine text and images from various applications such as the Adobe Photoshop®, Adobe Illustrator®, and Adobe InDesign® computer programs (all available from Adobe Systems Incorporated, of San Jose, California) to create professional graphic documents.
  • images may be created in Adobe Photoshop®, while line art may be created in Adobe Illustrator®, and the entire page layout may be synthesized in Adobe InDesign®.
  • a finished graphic document may be printed on a specifications for web offset publications (SWOP) press or other cyan, magenta, yellow, and black (CMYK) based output device.
  • SWOP web offset publications
  • CMSYK cyan, magenta, yellow, and black
  • elements such as images, fills, line art, and text may move from one application to another until they take their final form and the entire document is sent to a printer.
  • Most modern graphics applications include color management routines that perform some degree of color management, or manipulation of the colors of objects within a document, as the document is imported into, and exported out of, the applications.
  • Color management routines are designed to reconcile the different color capabilities of the various scanners, monitors, cameras, and printers that may create or handle an object or a document as the object or document travels along its workflow.
  • color management routines include routines to read and write device profiles, and to render colors from a source color space associated with a source device to a destination color space associated with a destination device.
  • Device profiles define the color characteristics of the source and destination devices, and are used by the color management routines to map object colors from the source color space to the destination color space through an intermediate, device independent, color space.
  • the color management routines may be available in the destination color space. Colors that are available in the source color space but unavailable in the destination color space are mapped to an appropriate destination color available in the destination color space by the color management routines.
  • colors associated with objects in a document may undergo subtle changes as the document moves along its workflow. While color management induced color changes are useful for many objects in a document, it is important that some objects retain their color throughout a document's workflow. For example, a black or neutral gray text object incorporated into a document as a label ought to retain its neutral color throughout the document's workflow. By retaining its color, such an object will be printed using only a printer's black ink, and will therefore appear in print to have a neutral black or gray color as intended.
  • the colors of all objects in a document are color managed or manipulated throughout the document's workflow by the color management routines of each application handling the document.
  • text objects created with neutral grays and blacks may lose their "grayness" over the course of the workflow, and be printed with non-neutral colors.
  • a black text object created in an RGB color space in one application may be transformed to an HSB color space in another application and back to an RGB color space of a third application as the document containing the text object moves along its workflow.
  • the object will not be printed with the printer's black ink alone, but will be printed with an admixture of the printer's cyan, yellow, or magenta inks. Thus, the object will lose its intended neutral gray color in print.
  • the invention discloses a gray preservation method and apparatus for preserving neutral gray colors in electronic documents.
  • An application using the gray preservation method receives an electronic document containing a variety of objects having a variety of object types.
  • Composite objects are reduced to their irreducible component objects, and the irreducible component objects are individually subjected to the gray preservation method.
  • Objects of a type which require gray preservation are selected, while objects of a type which do not require gray preservation are not further processed.
  • Objects of a type which require gray preservation are text, line, curve, fill, gradient, bitmap, and image objects.
  • Objects of a type which require gray preservation are tested for grayness. The test for grayness is conducted in the color space in which the selected objects' colors are represented. Alternatively, the objects' colors are converted to a device independent color space, and the test for grayness is conducted in the device independent color space.
  • the gray color test applied to objects represented in a given color space exploits the manner in which gray colored objects are represented in that color space.
  • the test can be strict or relaxed.
  • the strict test requires gray objects have their colors represented exactly as gray colored objects are represented in the given color space.
  • the relaxed test requires gray objects have their colors approximately represented as gray colored objects are represented in the given color space.
  • the strict and relaxed gray color tests for objects whose colors are represented in an RGB color space require the objects' colors have red, green, and blue components which are exactly and approximately equal to each other, respectively.
  • the strict and relaxed gray color tests for objects whose colors are represented in a CMYK color space require the objects' colors have cyan, magenta, and yellow components which are exactly and approximately equal to zero, respectively.
  • the strict and relaxed gray color tests for objects whose colors are represented in a CIEXYZ color space require the objects' colors have X, Y, and Z components, normalized to the corresponding component in the diffuse white point, which are exactly and approximately equal to each other, respectively.
  • Objects that do not contain any grays fail the gray color test, and are not further processed.
  • Objects that contain a mixture of grays and other colors also fail the gray color test, and are not further processed.
  • Objects that contain only gray colors pass the gray color test, and are selected for gray preservation.
  • Gray preservation is accomplished by inhibiting color management for objects passing the gray color test. Color management is inhibited by converting the objects' colors to a color space which is not color managed by the application. Alternatively, color management is inhibited by tagging the objects to indicate they should not be color managed by the application.
  • FIG. 1 is a schematic illustration of a workflow used to create a graphic document.
  • FIG. 2 is a flow chart showing a method for preserving gray colors in certain types of objects in a color document.
  • Figure 1 illustrates a simple workflow in which the invention may be used.
  • the invention can be used in more sophisticated workflows, and the utility of the invention does not depend upon the type or sophistication of the workflow in which it is used.
  • a document containing an image object 104 is manipulated in an application running on a computer 103 to adjust the image's colors.
  • a second document containing a text object 102 is created in a second application running on a second computer 101.
  • the documents containing both text object 102 and image object 104 are sent to a third application running on a third computer 105 where they are combined to form a third document 106.
  • the combined document 106, containing image object 104 and associated text object 102 represents the final step in each object's workflow.
  • Finished document 106 is printed out on a color printer 107.
  • an application can implement a gray color preservation method such as the method schematically illustrated in Fig. 2. Because an application typically performs color management or manipulation on a document or object when the document or object is opened, saved, printed, or exported, or upon the importation of an external document or object, the method shown in Fig. 2 should be executed before a document or object is opened, saved, printed, or exported, or before importation of an external document or object.
  • an application having color management routines receives an electronic document (step 201).
  • the received electronic document contains a variety of objects having a variety of object types such as text, lines, curves, fills, gradients, bitmaps, compressed images, and sounds.
  • object types such as text, lines, curves, fills, gradients, bitmaps, compressed images, and sounds.
  • each object in the document is selected (step 202) by the gray preservation routine, tested for grayness (steps 205-206), and tested for its gray preservation requirements (step 207).
  • the gray preservation routine terminates (step 210).
  • the received electronic document (step 201) generally contains two broad categories of objects, irreducible objects and composite objects. Irreducible objects cannot be expressed as a combination of other objects. By contrast, composite objects are composed of other objects, and therefore can be expressed as a combination of other objects.
  • a glyph is an irreducible object.
  • a glyph is a bitmap representation of a character in a given font.
  • a text object consisting of a character string having a font attribute
  • a character string having a font attribute is a string of glyphs, where each glyph represents a different character in the string.
  • the gray preservation routine of Fig. 2 selects (step 202) and identifies (step 207) irreducible objects requiring gray preservation. When composite objects are encountered, the gray preservation routine processes each component object separately to determine its gray preservation requirements.
  • the gray preservation routine tests selected objects (step 202) for grayness in either their current color space or in a device independent color space (steps 203-205).
  • selected objects are tested for grayness in a device independent color space.
  • each object has its color or colors converted to a device independent color space (step 204) prior to having its color or colors tested for grayness (step 205).
  • the object's color can be converted to any device independent color space, including any of the CIEbased color spaces such as CIEbasedABC, CIEbasedDEF, CIEbasedDEFG, CIELAB, or CIEXYZ.
  • the object's color is converted to the CIEXYZ color space.
  • selected objects have their colors tested in their current color space.
  • selected objects have their colors tested in either a device independent color space or in a current color space according to user preference.
  • the application provides the user with means to input preferences, including the preference for testing objects for grayness in a local color space or in a device independent color space.
  • User preferences can be selected on an object by object basis, or on a document by document basis.
  • the user preference means can be a graphical user interface, or any other form of data input.
  • the gray preservation routine tests selected objects for grayness (step 205) using appropriate tests for the color space in which the selected objects' colors are represented. As a general rule, every color space represents various shades of gray according to a well defined color scheme. The scheme used by a particular color space to represent shades of gray within that color space is exploited by the gray preservation routine to test whether a given object whose color is represented in that color space is gray.
  • RGB color spaces represent gray colored objects with RGB 3 -tuples having equal red, green, and blue components.
  • the RGB triplet (5,5,5) represents one shade of gray
  • the RGB triplet (17,17,17) represents another shade of gray.
  • CMYK color spaces represent gray colored objects with CMYK 4-tuples having cyan, magenta, and yellow components which are identically zero.
  • the CMYK 4-tuple (0,0,0,5) represents one shade of gray
  • the CMYK 4-tuple (0,0,0,17) represents another shade of gray.
  • the tests for grayness in device independent color spaces are similar.
  • gray colored objects are represented by 3 -tuples having equal X, Y, and Z tristimulus components when normalized to the tristimulus representation of the diffuse white point, (X W ,Y W ,Z W ).
  • the gray test is strict.
  • a strict color test requires an exact match to the color space's scheme for representing gray objects.
  • the gray test is relaxed.
  • an object's color representation need only approximately match the color space's scheme for representing gray colored objects.
  • one relaxed color test for a gray object represented in an RGB color space requires the components of the object's RGB 3 -tuple obey the relationships:
  • R/B 1 ⁇ ⁇ , where ⁇ and ⁇ are two small numbers. Typically, ⁇ and ⁇ are on the order of a few percent. However, larger or smaller values can be used. Similarly, other relaxed tests can be used. For example, R/G and R/B in equations (1) and (2) can be replaced with G/R and G/B. Other variations can be used that realize: R ⁇ G ⁇ B.
  • Relaxed color tests can be performed in different color spaces as well.
  • one relaxed color test in a CMYK color space requires the components of the object's CMYK 4-tuple obey the relationships:
  • the gray color test performed in step 205 is a relaxed color test only if the test is performed in a device independent color space, such as the CIEbased CIEXYZ color space.
  • a relaxed color test for a gray colored object represented in a CIEXYZ color space requires the normalized components of the object's CIEXYZ 3 -tuple obey the relationships:
  • the gray preservation routine determines if the object contains gray colors (step 206). An object contains gray colors if one or more of the colors associated with the object passes the gray color test. If the selected object does not contain gray colors, the gray preservation routine checks whether all of the objects within the received document have been tested (step 209). If all of the objects have been tested, the gray preservation routine terminates (step 210). Otherwise, it selects a new object to test (step 202). If the selected object contains gray colors (step 206), the gray preservation routine checks whether the object requires gray preservation (step 207). If the object does not require gray preservation (step 207), the gray preservation routine checks whether all of the objects within the received document have been tested (step 209).
  • the gray preservation routine terminates (step 210). Otherwise, it selects a new object to test (step 202). In general, not all objects containing gray colors (step 206) will require gray preservation (step 208). Instead, certain types of objects will almost always require gray preservation, while other types of objects will only occasionally require gray preservation. Objects that almost always require gray preservation tend to be objects possessing a single color attribute, or single color. Examples include text, line, curve, and fill objects. Objects that only occasionally require gray preservation, tend to be objects that possess multiple color attributes, or multiple colors. Examples include gradients, bitmaps, and image objects.
  • Objects having multiple color attributes which only contain gray colors generally require gray preservation.
  • a gray-scale gradient containing only neutral gray colors requires gray preservation to ensure that its grays are not altered or colorized by color management routines.
  • objects having multiple color attributes which contain some gray and some non-gray colors generally do not require gray preservation.
  • a color gradient from red to gray to green will not require gray preservation because many of the colors along the gradient will be shifted by color management routines. If neutral gray colors in the gradient are shifted to non-neutral colors by the color management routines, it is likely that nearby non-neutral colors in the gradient will be shifted to neutral gray colors by the same routines.
  • the neutral gray colors to shift, i.e. by turning off gray preservation for the color gradient, the continuity and density of all of the colors in the gradient is better preserved.
  • the gray preservation routine preserves the object's gray color (step 208) by inhibiting color management in its associated application.
  • the gray preservation routine inhibits color management by flagging the object, or by associating an attribute with the object, indicating that the object is not to be color managed.
  • the gray preservation routine inhibits color management of identified gray colored objects by converting the colors of the objects to a color space that is not color managed by its associated application, or by any of the other applications handling the object along the object's workflow. For example, Adobe's DeviceCMYK color space is not color managed by the Adobe Photoshop®, Illustrator®, or InDesign® applications.
  • color management of gray colored objects identified as requiring gray preservation can be inhibited by storing the objects' colors in Adobe's DeviceCMYK color space.
  • Other methods of inhibiting color management can also be used.
  • This invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them.
  • Apparatus of the invention can be implemented in a computer program product tangibly embodied in a machine- readable storage device for execution by a programmable processor; and method steps of the invention can be performed by a programmable processor executing a program of instructions to perform functions of the invention by operating on input data and generating output.
  • the invention can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device.
  • Each computer program can be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired; and in any case, the language can be a compiled or interpreted language.
  • Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, a processor will receive instructions and data from a readonly memory and/or a random access memory.
  • a computer will include one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks.
  • Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non- volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits).
  • ASICs application-specific integrated circuits
  • the invention can be implemented on a computer system having a display device such as a monitor or LCD screen for displaying information to the user and a keyboard and a pointing device such as a mouse or a trackball by which the user can provide input to the computer system.
  • the computer system can be programmed to provide a graphical user interface through which computer programs interact with users.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Facsimile Image Signal Circuits (AREA)
  • Image Processing (AREA)

Abstract

La présente invention concerne un procédé et un appareil permettant de préserver les couleurs grises dans un document électronique. Ce procédé consiste à recevoir un document électronique contenant une pluralité d'objets qui présente une pluralité de types d'objets. Il consiste ensuite à sélectionner les objets d'un type qui nécessitent une préservation du gris. Les couleurs des objets sélectionnés sont testés pour permettre de déterminer la présence de gris. L'essai de coloration grise est réalisé dans un espace de couleur local, ou en variante, dans un espace de couleur indépendant du dispositif après conversion des couleurs d'objets en espace de couleur indépendant du dispositif. L'essai de coloration grise dans l'espace d'essai de coloration est un essai de coloration strict, ou en variante, un essai de coloration non strict. Les objets qui ne contiennent que de la couleur grise sont identifiés, et leurs couleurs sont préservées par annulation de la gestion de leurs couleurs. La gestion de couleur est annulée par sauvegarde des couleurs d'objets dans un espace de coloration qui n'est pas soumis à une gestion de couleurs, ou dans en variante, par marquage des objets ou par affectation d'un attribut aux objets afin d'indiquer les objets qui ne doivent pas être soumis à une gestion de couleurs.
PCT/US2000/041337 2000-10-19 2000-10-19 Preservation des couleurs grises WO2002033957A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/US2000/041337 WO2002033957A1 (fr) 2000-10-19 2000-10-19 Preservation des couleurs grises
US10/168,057 US6930690B1 (en) 2000-10-19 2000-10-19 Preserving gray colors

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2000/041337 WO2002033957A1 (fr) 2000-10-19 2000-10-19 Preservation des couleurs grises

Publications (1)

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WO2002033957A1 true WO2002033957A1 (fr) 2002-04-25

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008036669A1 (fr) * 2006-09-20 2008-03-27 Qualcomm Incorporated Élimination automatique des couleurs dans une image capturée numériquement

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
No relevant documents disclosed *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008036669A1 (fr) * 2006-09-20 2008-03-27 Qualcomm Incorporated Élimination automatique des couleurs dans une image capturée numériquement
US7903869B2 (en) 2006-09-20 2011-03-08 Qualcomm Incorporated Automatic color removal in digitally captured image technical field

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