java.awt.color
Class ICC_ColorSpace

java.lang.Object
  |
  +--java.awt.color.ColorSpace
        |
        +--java.awt.color.ICC_ColorSpace

All Implemented Interfaces:

Serializable

public class ICC_ColorSpace

extends ColorSpace

An implementation of the abstract ColorSpace class. This representation of device independent and device dependent color spaces is based on the International Color Consortium Specification ICC.1:1998-09, File Format for Color Profiles, September 1998, and the addendum ICC.1A:1999-04, April 1999, to that specification (see http://www.color.org).

Typically, a Color or ColorModel would be associated with an ICC Profile which is either an input, display, or output profile (see the ICC specification). There are other types of ICC Profiles, e.g. abstract profiles, device link profiles, and named color profiles, which do not contain information appropriate for representing the color space of a color, image, or device (see ICC_Profile). Attempting to create an ICC_ColorSpace object from an inappropriate ICC Profile is an error.

ICC Profiles represent transformations from the color space of the profile (e.g. a monitor) to a Profile Connection Space (PCS). Profiles of interest for tagging images or colors have a PCS which is one of the device independent spaces (one CIEXYZ space and two CIELab spaces) defined in the ICC Profile Format Specification. Most profiles of interest either have invertible transformations or explicitly specify transformations going both directions. Should an ICC_ColorSpace object be used in a way requiring a conversion from PCS to the profile's native space and there is inadequate data to correctly perform the conversion, the ICC_ColorSpace object will produce output in the specified type of color space (e.g. TYPE_RGB, TYPE_CMYK, etc.), but the specific color values of the output data will be undefined.

The details of this class are not important for simple applets, which draw in a default color space or manipulate and display imported images with a known color space. At most, such applets would need to get one of the default color spaces via ColorSpace.getInstance().

See Also:

ColorSpace, ICC_Profile, Serialized Form

Fields inherited from class java.awt.color.ColorSpace

CS_CIEXYZ, CS_GRAY, CS_LINEAR_RGB, CS_PYCC, CS_sRGB, TYPE_2CLR, TYPE_3CLR, TYPE_4CLR, TYPE_5CLR, TYPE_6CLR, TYPE_7CLR, TYPE_8CLR, TYPE_9CLR, TYPE_ACLR, TYPE_BCLR, TYPE_CCLR, TYPE_CMY, TYPE_CMYK, TYPE_DCLR, TYPE_ECLR, TYPE_FCLR, TYPE_GRAY, TYPE_HLS, TYPE_HSV, TYPE_Lab, TYPE_Luv, TYPE_RGB, TYPE_XYZ, TYPE_YCbCr, TYPE_Yxy

Constructor Summary

ICC_ColorSpace(ICC_Profile profile)
Constructs a new ICC_ColorSpace from an ICC_Profile object.

Method Summary

float[]	fromCIEXYZ(float[] colorvalue) Transforms a color value assumed to be in the CS_CIEXYZ conversion color space into this ColorSpace.
float[]	fromRGB(float[] rgbvalue) Transforms a color value assumed to be in the default CS_sRGB color space into this ColorSpace.
ICC_Profile	getProfile() Returns the ICC_Profile for this ICC_ColorSpace.
float[]	toCIEXYZ(float[] colorvalue) Transforms a color value assumed to be in this ColorSpace into the CS_CIEXYZ conversion color space.
float[]	toRGB(float[] colorvalue) Transforms a color value assumed to be in this ColorSpace into a value in the default CS_sRGB color space.

Methods inherited from class java.awt.color.ColorSpace

getInstance, getName, getNumComponents, getType, isCS_sRGB

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ICC_ColorSpace

public ICC_ColorSpace(ICC_Profile profile)

Constructs a new ICC_ColorSpace from an ICC_Profile object.

Throws:

IllegalArgumentException - if profile is inappropriate for representing a ColorSpace.

Method Detail

getProfile

public ICC_Profile getProfile()

Returns the ICC_Profile for this ICC_ColorSpace.

toRGB

public float[] toRGB(float[] colorvalue)

Transforms a color value assumed to be in this ColorSpace into a value in the default CS_sRGB color space.

This method transforms color values using algorithms designed to produce the best perceptual match between input and output colors. In order to do colorimetric conversion of color values, you should use the toCIEXYZ method of this color space to first convert from the input color space to the CS_CIEXYZ color space, and then use the fromCIEXYZ method of the CS_sRGB color space to convert from CS_CIEXYZ to the output color space. See toCIEXYZ and fromCIEXYZ for further information.

Overrides:

toRGB in class ColorSpace

Parameters:

colorvalue - a float array with length of at least the number of components in this ColorSpace.

Returns:

a float array of length 3.

fromRGB

public float[] fromRGB(float[] rgbvalue)

Transforms a color value assumed to be in the default CS_sRGB color space into this ColorSpace.

This method transforms color values using algorithms designed to produce the best perceptual match between input and output colors. In order to do colorimetric conversion of color values, you should use the toCIEXYZ method of the CS_sRGB color space to first convert from the input color space to the CS_CIEXYZ color space, and then use the fromCIEXYZ method of this color space to convert from CS_CIEXYZ to the output color space. See toCIEXYZ and fromCIEXYZ for further information.

Overrides:

fromRGB in class ColorSpace

Parameters:

rgbvalue - a float array with length of at least 3.

Returns:

a float array with length equal to the number of components in this ColorSpace.

toCIEXYZ

public float[] toCIEXYZ(float[] colorvalue)

Transforms a color value assumed to be in this ColorSpace into the CS_CIEXYZ conversion color space.

This method transforms color values using relative colorimetry, as defined by the ICC Specification. This means that the XYZ values returned by this method are represented relative to the D50 white point of the CS_CIEXYZ color space. This representation is useful in a two-step color conversion process in which colors are transformed from an input color space to CS_CIEXYZ and then to an output color space. This representation is not the same as the XYZ values that would be measured from the given color value by a colorimeter. A further transformation is necessary to compute the XYZ values that would be measured using current CIE recommended practices. The paragraphs below explain this in more detail.

The ICC standard uses a device independent color space (DICS) as the mechanism for converting color from one device to another device. In this architecture, colors are converted from the source device's color space to the ICC DICS and then from the ICC DICS to the destination device's color space. The ICC standard defines device profiles which contain transforms which will convert between a device's color space and the ICC DICS. The overall conversion of colors from a source device to colors of a destination device is done by connecting the device-to-DICS transform of the profile for the source device to the DICS-to-device transform of the profile for the destination device. For this reason, the ICC DICS is commonly referred to as the profile connection space (PCS). The color space used in the methods toCIEXYZ and fromCIEXYZ is the CIEXYZ PCS defined by the ICC Specification. This is also the color space represented by ColorSpace.CS_CIEXYZ.

The XYZ values of a color are often represented as relative to some white point, so the actual meaning of the XYZ values cannot be known without knowing the white point of those values. This is known as relative colorimetry. The PCS uses a white point of D50, so the XYZ values of the PCS are relative to D50. For example, white in the PCS will have the XYZ values of D50, which is defined to be X=.9642, Y=1.000, and Z=0.8249. This white point is commonly used for graphic arts applications, but others are often used in other applications.

To quantify the color characteristics of a device such as a printer or monitor, measurements of XYZ values for particular device colors are typically made. For purposes of this discussion, the term device XYZ values is used to mean the XYZ values that would be measured from device colors using current CIE recommended practices.

Converting between device XYZ values and the PCS XYZ values returned by this method corresponds to converting between the device's color space, as represented by CIE colorimetric values, and the PCS. There are many factors involved in this process, some of which are quite subtle. The most important, however, is the adjustment made to account for differences between the device's white point and the white point of the PCS. There are many techniques for doing this and it is the subject of much current research and controversy. Some commonly used methods are XYZ scaling, the von Kries transform, and the Bradford transform. The proper method to use depends upon each particular application.

The simplest method is XYZ scaling. In this method each device XYZ value is converted to a PCS XYZ value by multiplying it by the ratio of the PCS white point (D50) to the device white point.

 
 Xd, Yd, Zd are the device XYZ values
 Xdw, Ydw, Zdw are the device XYZ white point values
 Xp, Yp, Zp are the PCS XYZ values
 Xd50, Yd50, Zd50 are the PCS XYZ white point values
 
 Xp = Xd * (Xd50 / Xdw)
 Yp = Yd * (Yd50 / Ydw)
 Zp = Zd * (Zd50 / Zdw)
 
 

Conversion from the PCS to the device would be done by inverting these equations:

 
 Xd = Xp * (Xdw / Xd50)
 Yd = Yp * (Ydw / Yd50)
 Zd = Zp * (Zdw / Zd50)
 
 

Note that the media white point tag in an ICC profile is not the same as the device white point. The media white point tag is expressed in PCS values and is used to represent the difference between the XYZ of device illuminant and the XYZ of the device media when measured under that illuminant. The device white point is expressed as the device XYZ values corresponding to white displayed on the device. For example, displaying the RGB color (1.0, 1.0, 1.0) on an sRGB device will result in a measured device XYZ value of D65. This will not be the same as the media white point tag XYZ value in the ICC profile for an sRGB device.

Overrides:

toCIEXYZ in class ColorSpace

Parameters:

colorvalue - a float array with length of at least the number of components in this ColorSpace.

Returns:

a float array of length 3.

fromCIEXYZ

public float[] fromCIEXYZ(float[] colorvalue)

Transforms a color value assumed to be in the CS_CIEXYZ conversion color space into this ColorSpace.

This method transforms color values using relative colorimetry, as defined by the ICC Specification. This means that the XYZ argument values taken by this method are represented relative to the D50 white point of the CS_CIEXYZ color space. This representation is useful in a two-step color conversion process in which colors are transformed from an input color space to CS_CIEXYZ and then to an output color space. The color values returned by this method are not those that would produce the XYZ value passed to the method when measured by a colorimeter. If you have XYZ values corresponding to measurements made using current CIE recommended practices, they must be converted to D50 relative values before being passed to this method. The paragraphs below explain this in more detail.

The ICC standard uses a device independent color space (DICS) as the mechanism for converting color from one device to another device. In this architecture, colors are converted from the source device's color space to the ICC DICS and then from the ICC DICS to the destination device's color space. The ICC standard defines device profiles which contain transforms which will convert between a device's color space and the ICC DICS. The overall conversion of colors from a source device to colors of a destination device is done by connecting the device-to-DICS transform of the profile for the source device to the DICS-to-device transform of the profile for the destination device. For this reason, the ICC DICS is commonly referred to as the profile connection space (PCS). The color space used in the methods toCIEXYZ and fromCIEXYZ is the CIEXYZ PCS defined by the ICC Specification. This is also the color space represented by ColorSpace.CS_CIEXYZ.

The XYZ values of a color are often represented as relative to some white point, so the actual meaning of the XYZ values cannot be known without knowing the white point of those values. This is known as relative colorimetry. The PCS uses a white point of D50, so the XYZ values of the PCS are relative to D50. For example, white in the PCS will have the XYZ values of D50, which is defined to be X=.9642, Y=1.000, and Z=0.8249. This white point is commonly used for graphic arts applications, but others are often used in other applications.

To quantify the color characteristics of a device such as a printer or monitor, measurements of XYZ values for particular device colors are typically made. For purposes of this discussion, the term device XYZ values is used to mean the XYZ values that would be measured from device colors using current CIE recommended practices.

Converting between device XYZ values and the PCS XYZ values taken as arguments by this method corresponds to converting between the device's color space, as represented by CIE colorimetric values, and the PCS. There are many factors involved in this process, some of which are quite subtle. The most important, however, is the adjustment made to account for differences between the device's white point and the white point of the PCS. There are many techniques for doing this and it is the subject of much current research and controversy. Some commonly used methods are XYZ scaling, the von Kries transform, and the Bradford transform. The proper method to use depends upon each particular application.

The simplest method is XYZ scaling. In this method each device XYZ value is converted to a PCS XYZ value by multiplying it by the ratio of the PCS white point (D50) to the device white point.

 
 Xd, Yd, Zd are the device XYZ values
 Xdw, Ydw, Zdw are the device XYZ white point values
 Xp, Yp, Zp are the PCS XYZ values
 Xd50, Yd50, Zd50 are the PCS XYZ white point values
 
 Xp = Xd * (Xd50 / Xdw)
 Yp = Yd * (Yd50 / Ydw)
 Zp = Zd * (Zd50 / Zdw)
 
 

Conversion from the PCS to the device would be done by inverting these equations:

 
 Xd = Xp * (Xdw / Xd50)
 Yd = Yp * (Ydw / Yd50)
 Zd = Zp * (Zdw / Zd50)
 
 

Note that the media white point tag in an ICC profile is not the same as the device white point. The media white point tag is expressed in PCS values and is used to represent the difference between the XYZ of device illuminant and the XYZ of the device media when measured under that illuminant. The device white point is expressed as the device XYZ values corresponding to white displayed on the device. For example, displaying the RGB color (1.0, 1.0, 1.0) on an sRGB device will result in a measured device XYZ value of D65. This will not be the same as the media white point tag XYZ value in the ICC profile for an sRGB device.

Overrides:

fromCIEXYZ in class ColorSpace

Parameters:

colorvalue - a float array with length of at least 3.

Returns:

a float array with length equal to the number of components in this ColorSpace.