net.sf.ij_plugins.color

Class ColorSpaceConversion

java.lang.Object

net.sf.ij_plugins.color.ColorSpaceConversion

public final class ColorSpaceConversion
extends java.lang.Object

Basic color space conversion utilities, assuming two degree observer and illuminant D65.

Author:

Jarek Sacha

Method Summary

Methods

Modifier and Type	Method and Description
static ij.process.ColorProcessor	labToColorProcessor(VectorProcessor vp) Convert between CIE L*a*b* and RGB color image representation.
static void	labToXYZ(float[] lab, float[] xyz) Conversion from CIE L*a*b* to CIE XYZ assuming Observer.
static VectorProcessor	labToXYZVectorProcessor(VectorProcessor vp) Convert between CIE L*a*b* and XYZ color image representation.
static VectorProcessor	rgbToLabVectorProcessor(ij.process.ColorProcessor cp) Convert between RGB and CIE L*a*b* color image representation.
static void	rgbToXYZ(float[] rgb, float[] xyz) sRGB to XYZ conversion based on conversion coefficients at: http://www.brucelindbloom.com/Eqn_RGB_to_XYZ.html See also conversion from sRGB to CIE XYZ as defined in the IEC 619602-1 standard (http://www.colour.org/tc8-05/Docs/colorspace/61966-2-1.pdf), though it uses approximated coefficients.
static VectorProcessor	rgbToXYZVectorProcessor(ij.process.ColorProcessor cp) Convert between sRGB and XYZ color image representation.
static ij.process.ByteProcessor[]	rgbToYCbCr(ij.process.ColorProcessor rgb) Converts image pixels from RGB color space to YCbCr color space.
static ij.process.ByteProcessor[]	rgbToYCbCr(ij.process.ColorProcessor src, ProgressListener progressListener) Converts image pixels from RGB color space to YCbCr color space.
static ij.process.ColorProcessor	xyzToColorProcessor(VectorProcessor vp) Convert between XYZ and RGB color image representation.
static void	xyzToLab(float[] xyz, float[] lab) Conversion from CIE XYZ to CIE L*a*b* assuming Observer.
static VectorProcessor	xyzToLabVectorProcessor(VectorProcessor vp) Convert between CIE XYZ and L*a*b* color image representation.
static void	xyzToRGB(float[] xyz, float[] rgb) XYZ to sRGB conversion based on conversion coefficients at: http://www.brucelindbloom.com/Eqn_XYZ_to_RGB.html Conversion from CIE XYZ to sRGB as defined in the IEC 619602-1 standard (http://www.colour.org/tc8-05/Docs/colorspace/61966-2-1.pdf)
static void	ycbcrToRGB(byte[] ybr, byte[] rgb) Converts image pixels from RGB color space to YCbCr color space.
static ij.process.ColorProcessor	ycbcrToRGB(ij.process.ByteProcessor[] ybr) Converts image pixels from RGB color space to YCbCr color space.
static ij.process.ColorProcessor	ycbcrToRGB(ij.process.ByteProcessor[] ybr, ProgressListener progressListener) Converts image pixels from RGB color space to YCbCr color space.

Methods inherited from class java.lang.Object

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

Method Detail

xyzToRGB

public static void xyzToRGB(float[] xyz,
            float[] rgb)

XYZ to sRGB conversion based on conversion coefficients at: http://www.brucelindbloom.com/Eqn_XYZ_to_RGB.html

Conversion from CIE XYZ to sRGB as defined in the IEC 619602-1 standard (http://www.colour.org/tc8-05/Docs/colorspace/61966-2-1.pdf)

 r_linear = +3.2404542 * X - 1.5371385 * Y - 0.4985314 * Z;
 g_linear = -0.9692660 * X + 1.8760108 * Y + 0.0415560 * Z;
 b_linear = +0.0556434 * X - 0.2040259 * Y + 1.0572252 * Z;
 r = r_linear > 0.0031308
       ? 1.055 * Math.pow(r_linear, (1 / 2.4)) - 0.055
       : 12.92 * r_linear;
 g = g_linear > 0.0031308
       ? 1.055 * Math.pow(g_linear, (1 / 2.4)) - 0.055
       : 12.92 * g_linear;
 b = b_linear > 0.0031308
       ? 1.055 * Math.pow(b_linear, (1 / 2.4)) - 0.055
       : 12.92 * b_linear;
 R = r * 255
 G = r * 255
 B = r * 255
 

Parameters:

xyz - input CIE XYZ values.

rgb - output sRGB values in [0, 255] range.

labToXYZ

public static void labToXYZ(float[] lab,
            float[] xyz)

Conversion from CIE L*a*b* to CIE XYZ assuming Observer. = 2°, Illuminant = D65. Conversion based on formulas provided at http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html

Parameters:

lab - input CIE L*a*b* values.

xyz - output CIE XYZ values.

rgbToXYZ

public static void rgbToXYZ(float[] rgb,
            float[] xyz)

sRGB to XYZ conversion based on conversion coefficients at: http://www.brucelindbloom.com/Eqn_RGB_to_XYZ.html
See also conversion from sRGB to CIE XYZ as defined in the IEC 619602-1 standard (http://www.colour.org/tc8-05/Docs/colorspace/61966-2-1.pdf), though it uses approximated coefficients.

 r = R / 255;
 g = G / 255;
 b = B / 255;
 r_linear = r > 0.04045
          ? Math.pow((r + 0.055) / 1.055, 2.4)
          : r / 12.92;
 g_linear = g > 0.04045
          ? Math.pow((g + 0.055) / 1.055, 2.4)
          : g / 12.92;
 b_linear = b > 0.04045
          ? Math.pow((b + 0.055) / 1.055, 2.4)
          : b / 12.92;
 X = 0.4124564 * r_linear + 0.3575761 * g_linear + 0.1804375 * b_linear;
 Y = 0.2126729 * r_linear + 0.7151522 * g_linear + 0.0721750 * b_linear;
 Z = 0.0193339 * r_linear + 0.1191920 * g_linear + 0.9503041 * b_linear;
 

Parameters:

rgb - source sRGB values. Size of array rgb must be at least 3. If size of array rgb larger than three then only first 3 values are used.

xyz - destination CIE XYZ values. Size of array xyz must be at least 3. If size of array xyz larger than three then only first 3 values are used.

xyzToLab

public static void xyzToLab(float[] xyz,
            float[] lab)

Conversion from CIE XYZ to CIE L*a*b* assuming Observer. = 2°, Illuminant = D65. Conversion based on formulas provided at http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html

Parameters:

xyz - source CIE XYZ values. Size of array xyz must be at least 3. If size of array xyz larger than three then only first 3 values are used.

lab - destination CIE L*a*b* values. Size of array lab must be at least 3. If size of array lab larger than three then only first 3 values are used.

rgbToLabVectorProcessor

public static VectorProcessor rgbToLabVectorProcessor(ij.process.ColorProcessor cp)

Convert between RGB and CIE L*a*b* color image representation.

Parameters:

cp - RGB image to be converted

Returns:

CIE L*a*b* image represented by VectorProcessor.

rgbToXYZVectorProcessor

public static VectorProcessor rgbToXYZVectorProcessor(ij.process.ColorProcessor cp)

Convert between sRGB and XYZ color image representation.

Parameters:

cp - RGB image to be converted

Returns:

XYZ image represented by VectorProcessor.

labToColorProcessor

public static ij.process.ColorProcessor labToColorProcessor(VectorProcessor vp)

Convert between CIE L*a*b* and RGB color image representation.

Parameters:

vp - CIE L*a*b* image represented by VectorProcessor.

Returns:

RGB image represented by a ColorProcessor.

labToXYZVectorProcessor

public static VectorProcessor labToXYZVectorProcessor(VectorProcessor vp)

Convert between CIE L*a*b* and XYZ color image representation.

Parameters:

vp - L*a*b* image represented by VectorProcessor.

Returns:

XYZ image represented by a VectorProcessor.

xyzToColorProcessor

public static ij.process.ColorProcessor xyzToColorProcessor(VectorProcessor vp)

Convert between XYZ and RGB color image representation.

Parameters:

vp - XYZ image represented by VectorProcessor.

Returns:

RGB image represented by a ColorProcessor.

xyzToLabVectorProcessor

public static VectorProcessor xyzToLabVectorProcessor(VectorProcessor vp)

Convert between CIE XYZ and L*a*b* color image representation.

Parameters:

vp - XYZ image represented by VectorProcessor.

Returns:

L*a*b* image represented by a VectorProcessor.

rgbToYCbCr

public static ij.process.ByteProcessor[] rgbToYCbCr(ij.process.ColorProcessor src,
                                    ProgressListener progressListener)

Converts image pixels from RGB color space to YCbCr color space. Uses formulas provided at: http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC30. See also: http://en.wikipedia.org/wiki/YCbCr.

YCbCb (601) from "digital 8-bit RGB "

 ========================================================================
 Y  = 16  + 1/256 * (   65.738  * R +  129.057  * G +  25.064  * B)
 Cb = 128 + 1/256 * ( - 37.945  * R -   74.494  * G + 112.439  * B)
 Cr = 128 + 1/256 * (  112.439  * R -   94.154  * G -  18.285  * B)
 ........................................................................
 R, G, B          in {0, 1, 2, ..., 255}
 Y                in {16, 17, ..., 235}
    with footroom in {1, 2, ..., 15}
         headroom in {236, 237, ..., 254}
         sync.    in {0, 255}
 Cb, Cr           in {16, 17, ..., 240}
 

Parameters:

src - source image.

progressListener - progress listener.

Returns:

array of color bands: Y, Cb, Cr, respectively.

rgbToYCbCr

public static ij.process.ByteProcessor[] rgbToYCbCr(ij.process.ColorProcessor rgb)

Converts image pixels from RGB color space to YCbCr color space. Equivalent to calling rgbToYCbCr(rgb, null).

Parameters:

rgb - input image in sRGB color space.

Returns:

array of ByteProcessor representing color planes: Y, Cb, and Cr.

See Also:

rgbToYCbCr(ij.process.ColorProcessor, net.sf.ij_plugins.util.progress.ProgressListener)

ycbcrToRGB

public static void ycbcrToRGB(byte[] ybr,
              byte[] rgb)

Converts image pixels from RGB color space to YCbCr color space. Uses formulas provided at: http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC30. See also: http://en.wikipedia.org/wiki/YCbCr.

"digital 8-bit RGB" from YCbCb (601)

 ========================================================================
 R = 1/256 * (298.081952524118 * (Y -16) +   0.001711624973 * (Cb - 128) + 408.582641764512 * (Cr-128))
 G = 1/256 * (298.081952524118 * (Y -16) - 100.290891128080 * (Cb - 128) - 208.120396471735 * (Cr-128))
 B = 1/256 * (298.081952524118 * (Y -16) + 516.412147108167 * (Cb - 128) -   0.000466679809 * (Cr-128))
 

Parameters:

ybr - source Y, Cb, and Cr (cannot ne null).

rgb - destination RGB (cannot be null).

ycbcrToRGB

public static ij.process.ColorProcessor ycbcrToRGB(ij.process.ByteProcessor[] ybr,
                                   ProgressListener progressListener)

Converts image pixels from RGB color space to YCbCr color space. Uses formulas provided at: http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC30. See also: http://en.wikipedia.org/wiki/YCbCr.

"digital 8-bit RGB" from YCbCb (601)

 ========================================================================
 R = 1/256 * (298.081952524118 * (Y -16) +   0.001711624973 * (Cb - 128) + 408.582641764512 * (Cr-128))
 G = 1/256 * (298.081952524118 * (Y -16) - 100.290891128080 * (Cb - 128) - 208.120396471735 * (Cr-128))
 B = 1/256 * (298.081952524118 * (Y -16) + 516.412147108167 * (Cb - 128) -   0.000466679809 * (Cr-128))
 

Parameters:

ybr - source image, array of color bands: Y, Cb, Cr, respectively.

progressListener - progress listener, can be null.

Returns:

RGB image.

ycbcrToRGB

public static ij.process.ColorProcessor ycbcrToRGB(ij.process.ByteProcessor[] ybr)

Converts image pixels from RGB color space to YCbCr color space. Equivalent to calling ycbcrToRGB(ybr, null).

Parameters:

ybr - array of ByteProcessor representing color planes: Y, Cb, and Cr.

Returns:

ColorProcessor representing image in sRGB color space.

See Also:

ycbcrToRGB(ij.process.ByteProcessor[], net.sf.ij_plugins.util.progress.ProgressListener)