Package icyllis.arc3d.core

Class ColorSpace

java.lang.Object
icyllis.arc3d.core.ColorSpace
Direct Known Subclasses:
ColorSpace.Rgb
public abstract class ColorSpace extends Object

A ColorSpace is used to identify a specific organization of colors. Each color space is characterized by a color model that defines how a color value is represented (for instance the RGB color model defines a color value as a triplet of numbers).

Each component of a color must fall within a valid range, specific to each color space, defined by getMinValue(int) and getMaxValue(int) This range is commonly \([0..1]\). While it is recommended to use values in the valid range, a color space always clamps input and output values when performing operations such as converting to a different color space.

Using color spaces

This implementation provides a pre-defined set of common color spaces described in the ColorSpace.Named enum. To obtain an instance of one of the pre-defined color spaces, simply invoke get(Named):


 ColorSpace sRgb = ColorSpace.get(ColorSpace.Named.SRGB);

The get(Named) method always returns the same instance for a given name. Color spaces with an RGB color model can be safely cast to ColorSpace.Rgb. Doing so gives you access to more APIs to query various properties of RGB color models: color gamut primaries, transfer functions, conversions to and from linear space, etc. Please refer to ColorSpace.Rgb for more information.

The documentation of ColorSpace.Named provides a detailed description of the various characteristics of each available color space.

Color space conversions

To allow conversion between color spaces, this implementation uses the CIE XYZ profile connection space (PCS). Color values can be converted to and from this PCS using toXyz(float[]) and fromXyz(float[]).

For color space with a non-RGB color model, the white point of the PCS must be the CIE standard illuminant D50. RGB color spaces use their native white point (D65 for sRGB for instance and must undergo chromatic adaptation as necessary.

Since the white point of the PCS is not defined for RGB color space, it is highly recommended to use the variants of the connect(ColorSpace, ColorSpace) method to perform conversions between color spaces. A color space can be manually adapted to a specific white point using adapt(ColorSpace, float[]). Please refer to the documentation of RGB color spaces for more information. Several common CIE standard illuminants are provided in this class as reference (see ILLUMINANT_D65 or ILLUMINANT_D50 for instance).

Here is an example of how to convert from a color space to another:


 // Convert from DCI-P3 to Rec.2020
 ColorSpace.Connector connector = ColorSpace.connect(
         ColorSpace.get(ColorSpace.Named.DCI_P3),
         ColorSpace.get(ColorSpace.Named.BT2020));

 float[] bt2020 = connector.transform(p3r, p3g, p3b);

You can easily convert to sRGB by omitting the second parameter:


 // Convert from DCI-P3 to sRGB
 ColorSpace.Connector connector = ColorSpace.connect(ColorSpace.get(ColorSpace.Named.DCI_P3));

 float[] sRGB = connector.transform(p3r, p3g, p3b);

Conversions also work between color spaces with different color models:

 // Convert from CIE L*a*b* (color model Lab) to Rec.709 (color model RGB)
 ColorSpace.Connector connector = ColorSpace.connect(
         ColorSpace.get(ColorSpace.Named.CIE_LAB),
         ColorSpace.get(ColorSpace.Named.BT709));

Color spaces and multi-threading

Color spaces and other related classes (ColorSpace.Connector for instance) are immutable and stateless. They can be safely used from multiple concurrent threads.

Public static methods provided by this class, such as get(Named) and connect(ColorSpace, ColorSpace), are also guaranteed to be thread-safe.

See Also:

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static enum 
    ColorSpace.Adaptation
    static class 
    ColorSpace.Connector
    static enum 
    ColorSpace.Model
    A color model is required by a ColorSpace to describe the way colors can be represented as tuples of numbers.
    static enum 
    ColorSpace.Named
    List of common, named color spaces.
    static enum 
    ColorSpace.RenderIntent
    A render intent determines how a connector maps colors from one color space to another.
    static class 
    ColorSpace.Rgb

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final float[]
    ILLUMINANT_A
    Standard CIE 1931 2° illuminant A, encoded in xyY.
    static final float[]
    ILLUMINANT_B
    Standard CIE 1931 2° illuminant B, encoded in xyY.
    static final float[]
    ILLUMINANT_C
    Standard CIE 1931 2° illuminant C, encoded in xyY.
    static final float[]
    ILLUMINANT_D50
    Standard CIE 1931 2° illuminant D50, encoded in xyY.
    static final float[]
    ILLUMINANT_D55
    Standard CIE 1931 2° illuminant D55, encoded in xyY.
    static final float[]
    ILLUMINANT_D60
    Standard CIE 1931 2° illuminant D60, encoded in xyY.
    static final float[]
    ILLUMINANT_D65
    Standard CIE 1931 2° illuminant D65, encoded in xyY.
    static final float[]
    ILLUMINANT_D75
    Standard CIE 1931 2° illuminant D75, encoded in xyY.
    static final float[]
    ILLUMINANT_E
    Standard CIE 1931 2° illuminant E, encoded in xyY.
    static final int
    MAX_ID
    The maximum ID value a color space can have.
    static final int
    MIN_ID
    The minimum ID value a color space can have.

  • Method Summary

    Modifier and Type
    Method
    Description
    static ColorSpace
    adapt(ColorSpace colorSpace, float[] whitePoint)
    Performs the chromatic adaptation of a color space from its native white point to the specified white point.
    static ColorSpace
    adapt(ColorSpace colorSpace, float[] whitePoint, ColorSpace.Adaptation adaptation)
    Performs the chromatic adaptation of a color space from its native white point to the specified white point.
    static float[]
    adaptToIlluminantD50(float[] origWhitePoint, float[] origTransform)
    Helper method for internal color space transformation.
    static float[]
    cctToXyz(@org.jetbrains.annotations.Range(from=1L, to=2147483647L) int cct)
    Computes the chromaticity coordinates of a specified correlated color temperature (CCT) on the Planckian locus.
    static float[]
    chromaticAdaptation(ColorSpace.Adaptation adaptation, float[] srcWhitePoint, float[] dstWhitePoint)
    Computes the chromatic adaptation transform from the specified source white point to the specified destination white point.
    static ColorSpace.Connector
    connect(ColorSpace source)
    Connects the specified color spaces to sRGB.
    static ColorSpace.Connector
    connect(ColorSpace source, ColorSpace destination)
    Connects two color spaces to allow conversion from the source color space to the destination color space.
    static ColorSpace.Connector
    connect(ColorSpace source, ColorSpace.RenderIntent intent)
    Connects the specified color spaces to sRGB.
    static ColorSpace.Connector
    connect(ColorSpace source, ColorSpace destination, ColorSpace.RenderIntent intent)
    Connects two color spaces to allow conversion from the source color space to the destination color space.
    boolean
    equals(Object o)
     
    abstract float[]
    fromXyz(float[] v)
    Converts tristimulus values from the CIE XYZ space to this color space's color model.
    float[]
    fromXyz(float x, float y, float z)
    Converts tristimulus values from the CIE XYZ space to this color space's color model.
    static ColorSpace
    get(ColorSpace.Named name)
    Returns an instance of ColorSpace identified by the specified name.
    @org.jetbrains.annotations.Range(from=1L, to=4L) int
    getComponentCount()
    Returns the number of components that form a color value according to this color space's color model.
    @org.jetbrains.annotations.Range(from=-1L, to=63L) int
    getId()
    Returns the ID of this color space.
    abstract float
    getMaxValue(@org.jetbrains.annotations.Range(from=0L, to=3L) int component)
    Returns the maximum valid value for the specified component of this color space's color model.
    abstract float
    getMinValue(@org.jetbrains.annotations.Range(from=0L, to=3L) int component)
    Returns the minimum valid value for the specified component of this color space's color model.
    ColorSpace.Model
    getModel()
    Return the color model of this color space.
    String
    getName()
    Returns the name of this color space.
    int
    hashCode()
     
    boolean
    isSrgb()
    Indicates whether this color space is the sRGB color space or equivalent to the sRGB color space.
    abstract boolean
    isWideGamut()
    Returns whether this color space is a wide-gamut color space.
    static ColorSpace
    match(float[] toXYZD50, ColorSpace.Rgb.TransferParameters function)
    Returns a ColorSpace.Named instance of ColorSpace that matches the specified RGB to CIE XYZ transform and transfer functions.
    String
    toString()
    Returns a string representation of the object.
    abstract float[]
    toXyz(float[] v)
    Converts a color value from this color space's model to tristimulus CIE XYZ values.
    float[]
    toXyz(float r, float g, float b)
    Converts a color value from this color space's model to tristimulus CIE XYZ values.

    Methods inherited from class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait

  • Field Details

    • ILLUMINANT_A

      public static final float[] ILLUMINANT_A
      Standard CIE 1931 2° illuminant A, encoded in xyY. This illuminant has a color temperature of 2856K.

    • ILLUMINANT_B

      public static final float[] ILLUMINANT_B
      Standard CIE 1931 2° illuminant B, encoded in xyY. This illuminant has a color temperature of 4874K.

    • ILLUMINANT_C

      public static final float[] ILLUMINANT_C
      Standard CIE 1931 2° illuminant C, encoded in xyY. This illuminant has a color temperature of 6774K.

    • ILLUMINANT_D50

      public static final float[] ILLUMINANT_D50
      Standard CIE 1931 2° illuminant D50, encoded in xyY. This illuminant has a color temperature of 5003K. This illuminant is used by the profile connection space in ICC profiles.

    • ILLUMINANT_D55

      public static final float[] ILLUMINANT_D55
      Standard CIE 1931 2° illuminant D55, encoded in xyY. This illuminant has a color temperature of 5503K.

    • ILLUMINANT_D60

      public static final float[] ILLUMINANT_D60
      Standard CIE 1931 2° illuminant D60, encoded in xyY. This illuminant has a color temperature of 6004K.

    • ILLUMINANT_D65

      public static final float[] ILLUMINANT_D65
      Standard CIE 1931 2° illuminant D65, encoded in xyY. This illuminant has a color temperature of 6504K. This illuminant is commonly used in RGB color spaces such as sRGB, BT.209, etc.

    • ILLUMINANT_D75

      public static final float[] ILLUMINANT_D75
      Standard CIE 1931 2° illuminant D75, encoded in xyY. This illuminant has a color temperature of 7504K.

    • ILLUMINANT_E

      public static final float[] ILLUMINANT_E
      Standard CIE 1931 2° illuminant E, encoded in xyY. This illuminant has a color temperature of 5454K.

    • MIN_ID

      public static final int MIN_ID
      The minimum ID value a color space can have.
      See Also:

    • MAX_ID

      public static final int MAX_ID
      The maximum ID value a color space can have.
      See Also:

  • Method Details

    • getName

      @Nonnull public String getName()

      Returns the name of this color space. The name is never null and contains always at least 1 character.

      Color space names are recommended to be unique but are not guaranteed to be. There is no defined format but the name usually falls in one of the following categories:

      • Generic names used to identify color spaces in non-RGB color models. For instance: Generic L*a*b*.
      • Names tied to a particular specification. For instance: sRGB IEC61966-2.1 or SMPTE ST 2065-1:2012 ACES.
      • Ad-hoc names, often generated procedurally or by the user during a calibration workflow. These names often contain the make and model of the display.

      Because the format of color space names is not defined, it is not recommended to programmatically identify a color space by its name alone. Names can be used as a first approximation.

      It is however perfectly acceptable to display color space names to users in a UI, or in debuggers and logs. When displaying a color space name to the user, it is recommended to add extra information to avoid ambiguities: color model, a representation of the color space's gamut, white point, etc.

      Returns:
      A non-null String of length >= 1

    • getId

      public @org.jetbrains.annotations.Range(from=-1L, to=63L) int getId()
      Returns the ID of this color space. Positive IDs match the color spaces enumerated in ColorSpace.Named. A negative ID indicates a color space created by calling one of the public constructors.
      Returns:
      An integer between MIN_ID and MAX_ID

    • getModel

      @Nonnull public ColorSpace.Model getModel()
      Return the color model of this color space.
      Returns:
      A non-null ColorSpace.Model
      See Also:

    • getComponentCount

      public @org.jetbrains.annotations.Range(from=1L, to=4L) int getComponentCount()
      Returns the number of components that form a color value according to this color space's color model.
      Returns:
      An integer between 1 and 4
      See Also:

    • isWideGamut

      public abstract boolean isWideGamut()
      Returns whether this color space is a wide-gamut color space. An RGB color space is wide-gamut if its gamut entirely contains the sRGB gamut and if the area of its gamut is 90% of greater than the area of the NTSC gamut.
      Returns:
      True if this color space is a wide-gamut color space, false otherwise

    • isSrgb

      public boolean isSrgb()

      Indicates whether this color space is the sRGB color space or equivalent to the sRGB color space.

      A color space is considered sRGB if it meets all the following conditions:

      • Its color model is ColorSpace.Model.RGB.
      • Its primaries are within 1e-3 of the true sRGB primaries.
      • Its white point is within 1e-3 of the CIE standard illuminant D65.
      • Its opto-electronic transfer function is not linear.
      • Its electro-optical transfer function is not linear.
      • Its transfer functions yield values within 1e-3 of ColorSpace.Named.SRGB.
      • Its range is \([0..1]\).

      This method always returns true for ColorSpace.Named.SRGB.

      Returns:
      True if this color space is the sRGB color space (or a close approximation), false otherwise

    • getMinValue

      public abstract float getMinValue(@org.jetbrains.annotations.Range(from=0L, to=3L) int component)
      Returns the minimum valid value for the specified component of this color space's color model.
      Parameters:
      component - The index of the component
      Returns:
      A floating point value less than getMaxValue(int)
      See Also:

    • getMaxValue

      public abstract float getMaxValue(@org.jetbrains.annotations.Range(from=0L, to=3L) int component)
      Returns the maximum valid value for the specified component of this color space's color model.
      Parameters:
      component - The index of the component
      Returns:
      A floating point value greater than getMinValue(int)
      See Also:

    • toXyz

      @Nonnull @Size(3L) public float[] toXyz(float r, float g, float b)

      Converts a color value from this color space's model to tristimulus CIE XYZ values. If the color model of this color space is not RGB, it is assumed that the target CIE XYZ space uses a D50 standard illuminant.

      This method is a convenience for color spaces with a model of 3 components (RGB or ColorSpace.Model.LAB for instance). With color spaces using fewer or more components, use toXyz(float[]) instead

      .
      Parameters:
      r - The first component of the value to convert from (typically R in RGB)
      g - The second component of the value to convert from (typically G in RGB)
      b - The third component of the value to convert from (typically B in RGB)
      Returns:
      A new array of 3 floats, containing tristimulus XYZ values
      See Also:

    • toXyz

      @Nonnull @Size(min=3L) public abstract float[] toXyz(@Nonnull @Size(min=3L) float[] v)

      Converts a color value from this color space's model to tristimulus CIE XYZ values. If the color model of this color space is not RGB, it is assumed that the target CIE XYZ space uses a D50 standard illuminant.

      The specified array's length must be at least equal to to the number of color components as returned by ColorSpace.Model.getComponentCount().

      Parameters:
      v - An array of color components containing the color space's color value to convert to XYZ, and large enough to hold the resulting tristimulus XYZ values
      Returns:
      The array passed in parameter
      See Also:

    • fromXyz

      @Nonnull @Size(min=3L) public float[] fromXyz(float x, float y, float z)

      Converts tristimulus values from the CIE XYZ space to this color space's color model.

      Parameters:
      x - The X component of the color value
      y - The Y component of the color value
      z - The Z component of the color value
      Returns:
      A new array whose size is equal to the number of color components as returned by ColorSpace.Model.getComponentCount()
      See Also:

    • fromXyz

      @Nonnull @Size(min=3L) public abstract float[] fromXyz(@Nonnull @Size(min=3L) float[] v)

      Converts tristimulus values from the CIE XYZ space to this color space's color model. The resulting value is passed back in the specified array.

      The specified array's length must be at least equal to to the number of color components as returned by ColorSpace.Model.getComponentCount(), and its first 3 values must be the XYZ components to convert from.

      Parameters:
      v - An array of color components containing the XYZ values to convert from, and large enough to hold the number of components of this color space's model
      Returns:
      The array passed in parameter
      See Also:

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • toString

      @Nonnull public String toString()

      Returns a string representation of the object. This method returns a string equal to the value of:

       getName() + "(id=" + getId() + ", model=" + getModel() + ")"

      For instance, the string representation of the sRGB color space is equal to the following value:

       sRGB IEC61966-2.1 (id=0, model=RGB)
      Overrides:
      toString in class Object
      Returns:
      A string representation of the object

    • connect

      @Nonnull public static ColorSpace.Connector connect(@Nonnull ColorSpace source, @Nonnull ColorSpace destination)

      Connects two color spaces to allow conversion from the source color space to the destination color space. If the source and destination color spaces do not have the same profile connection space (CIE XYZ with the same white point), they are chromatically adapted to use the CIE standard illuminant D50 as needed.

      If the source and destination are the same, an optimized connector is returned to avoid unnecessary computations and loss of precision.

      Colors are mapped from the source color space to the destination color space using the perceptual render intent.

      Parameters:
      source - The color space to convert colors from
      destination - The color space to convert colors to
      Returns:
      A non-null connector between the two specified color spaces
      See Also:

    • connect

      @Nonnull public static ColorSpace.Connector connect(@Nonnull ColorSpace source, @Nonnull ColorSpace destination, @Nonnull ColorSpace.RenderIntent intent)

      Connects two color spaces to allow conversion from the source color space to the destination color space. If the source and destination color spaces do not have the same profile connection space (CIE XYZ with the same white point), they are chromatically adapted to use the CIE standard illuminant D50 as needed.

      If the source and destination are the same, an optimized connector is returned to avoid unnecessary computations and loss of precision.

      Parameters:
      source - The color space to convert colors from
      destination - The color space to convert colors to
      intent - The render intent to map colors from the source to the destination
      Returns:
      A non-null connector between the two specified color spaces
      See Also:

    • connect

      @Nonnull public static ColorSpace.Connector connect(@Nonnull ColorSpace source)

      Connects the specified color spaces to sRGB. If the source color space does not use CIE XYZ D65 as its profile connection space, the two spaces are chromatically adapted to use the CIE standard illuminant D50 as needed.

      If the source is the sRGB color space, an optimized connector is returned to avoid unnecessary computations and loss of precision.

      Colors are mapped from the source color space to the destination color space using the perceptual render intent.

      Parameters:
      source - The color space to convert colors from
      Returns:
      A non-null connector between the specified color space and sRGB
      See Also:

    • connect

      @Nonnull public static ColorSpace.Connector connect(@Nonnull ColorSpace source, @Nonnull ColorSpace.RenderIntent intent)

      Connects the specified color spaces to sRGB. If the source color space does not use CIE XYZ D65 as its profile connection space, the two spaces are chromatically adapted to use the CIE standard illuminant D50 as needed.

      If the source is the sRGB color space, an optimized connector is returned to avoid unnecessary computations and loss of precision.

      Parameters:
      source - The color space to convert colors from
      intent - The render intent to map colors from the source to the destination
      Returns:
      A non-null connector between the specified color space and sRGB
      See Also:

    • adapt

      @Nonnull public static ColorSpace adapt(@Nonnull ColorSpace colorSpace, @Nonnull @Size(min=2L,max=3L) float[] whitePoint)

      Performs the chromatic adaptation of a color space from its native white point to the specified white point.

      The chromatic adaptation is performed using the ColorSpace.Adaptation.BRADFORD matrix.

      The color space returned by this method always has an ID of MIN_ID.

      Parameters:
      colorSpace - The color space to chromatically adapt
      whitePoint - The new white point
      Returns:
      A ColorSpace instance with the same name, primaries, transfer functions and range as the specified color space
      See Also:

    • adapt

      @Nonnull public static ColorSpace adapt(@Nonnull ColorSpace colorSpace, @Nonnull @Size(min=2L,max=3L) float[] whitePoint, @Nonnull ColorSpace.Adaptation adaptation)

      Performs the chromatic adaptation of a color space from its native white point to the specified white point. If the specified color space does not have an RGB color model, or if the color space already has the target white point, the color space is returned unmodified.

      The chromatic adaptation is performed using the von Kries method described in the documentation of ColorSpace.Adaptation.

      The color space returned by this method always has an ID of MIN_ID.

      Parameters:
      colorSpace - The color space to chromatically adapt
      whitePoint - The new white point
      adaptation - The adaptation matrix
      Returns:
      A new color space if the specified color space has an RGB model and a white point different from the specified white point; the specified color space otherwise
      See Also:

    • get

      @Nonnull public static ColorSpace get(@Nonnull ColorSpace.Named name)

      Returns an instance of ColorSpace identified by the specified name. The list of names provided in the ColorSpace.Named enum gives access to a variety of common RGB color spaces.

      This method always returns the same instance for a given name.

      This method is thread-safe.

      Parameters:
      name - The name of the color space to get an instance of
      Returns:
      A non-null ColorSpace instance

    • match

      @Nullable public static ColorSpace match(@Nonnull @Size(9L) float[] toXYZD50, @Nonnull ColorSpace.Rgb.TransferParameters function)

      Returns a ColorSpace.Named instance of ColorSpace that matches the specified RGB to CIE XYZ transform and transfer functions. If no instance can be found, this method returns null.

      The color transform matrix is assumed to target the CIE XYZ space a D50 standard illuminant.

      Parameters:
      toXYZD50 - 3x3 column-major transform matrix from RGB to the profile connection space CIE XYZ as an array of 9 floats, cannot be null
      function - Parameters for the transfer functions
      Returns:
      A non-null ColorSpace if a match is found, null otherwise

    • adaptToIlluminantD50

      @Nonnull @Size(9L) public static float[] adaptToIlluminantD50(@Nonnull @Size(2L) float[] origWhitePoint, @Nonnull @Size(9L) float[] origTransform)
      Helper method for internal color space transformation.

      This essentially calls adapt on a ColorSpace that has not been fully created. It also does not fully create the adapted ColorSpace, but just returns the transform.

    • cctToXyz

      @Nonnull @Size(3L) public static float[] cctToXyz(@org.jetbrains.annotations.Range(from=1L, to=2147483647L) int cct)

      Computes the chromaticity coordinates of a specified correlated color temperature (CCT) on the Planckian locus. The specified CCT must be greater than 0. A meaningful CCT range is [1667, 25000].

      The transform is computed using the methods in Kang et al., Design of Advanced Color - Temperature Control System for HDTV Applications, Journal of Korean Physical Society 41, 865-871 (2002).

      Parameters:
      cct - The correlated color temperature, in Kelvin
      Returns:
      Corresponding XYZ values
      Throws:
      IllegalArgumentException - If cct is invalid

    • chromaticAdaptation

      @Nonnull @Size(9L) public static float[] chromaticAdaptation(@Nonnull ColorSpace.Adaptation adaptation, @Nonnull @Size(min=2L,max=3L) float[] srcWhitePoint, @Nonnull @Size(min=2L,max=3L) float[] dstWhitePoint)

      Computes the chromatic adaptation transform from the specified source white point to the specified destination white point.

      The transform is computed using the von Kries method, described in more details in the documentation of ColorSpace.Adaptation. The ColorSpace.Adaptation enum provides different matrices that can be used to perform the adaptation.

      Parameters:
      adaptation - The adaptation method
      srcWhitePoint - The white point to adapt from
      dstWhitePoint - The white point to adapt to
      Returns:
      A 3x3 matrix as a non-null array of 9 floats