# lab2xyz

Convert CIE 1976 L*a*b* to CIE 1931 XYZ

## Syntax

``xyz = lab2xyz(lab)``
``xyz = lab2xyz(lab,'WhitePoint',whitePoint)``

## Description

example

````xyz = lab2xyz(lab)` converts CIE 1976 L*a*b* values to CIE 1931 XYZ values (2° observer).```

example

````xyz = lab2xyz(lab,'WhitePoint',whitePoint)` specifies the reference white point of the illuminant.```

## Examples

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Convert an L*a*b* color value to XYZ using the default reference white point, D65.

`lab2xyz([50 10 -5])`
```ans = 1×3 0.1942 0.1842 0.2282 ```

Convert an L*a*b* color value to XYZ specifying the D50 whitepoint.

`lab2xyz([50 10 -5],'WhitePoint','d50')`
```ans = 1×3 0.1970 0.1842 0.1729 ```

## Input Arguments

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Color values to convert, specified as a numeric array in one of these formats.

• c-by-3 colormap. Each row specifies one L*a*b* color value.

• m-by-n-by-3 image

• m-by-n-by-3-by-p stack of images

AttributeDescription
L*Luminance or brightness of the image. Values are in the range [0, 100], where 0 specifies black and 100 specifies white. As L* increases, colors become brighter.
a*Amount of red or green tones in the image. A large positive a* value corresponds to red/magenta. A large negative a* value corresponds to green. Although there is no single range for a*, values commonly fall in the range [-100, 100] or [-128, 127).
b*Amount of yellow or blue tones in the image. A large positive b* value corresponds to yellow. A large negative b* value corresponds to blue. Although there is no single range for b*, values commonly fall in the range [-100, 100] or [-128, 127).

Data Types: `single` | `double`

Reference white point, specified as a 1-by-3 vector or one of the CIE standard illuminants listed in the table.

ValueWhite Point
`"a"`

CIE standard illuminant A, `[1.0985, 1.0000, 0.3558]`. Simulates typical, domestic, tungsten-filament lighting with correlated color temperature of 2856 K.

`"c"`CIE standard illuminant C, `[0.9807, 1.0000, 1.1822]`. Simulates average or north sky daylight with correlated color temperature of 6774 K. Deprecated by CIE.
`"e"`Equal-energy radiator, `[1.000, 1.000, 1.000]`. Useful as a theoretical reference.
`"d50"`CIE standard illuminant D50, `[0.9642, 1.0000, 0.8251]`. Simulates warm daylight at sunrise or sunset with correlated color temperature of 5003 K. Also known as horizon light.

`"d55"`

CIE standard illuminant D55, `[0.9568, 1.0000, 0.9214]`. Simulates mid-morning or mid-afternoon daylight with correlated color temperature of 5500 K.

`"d65"`CIE standard illuminant D65, `[0.9504, 1.0000, 1.0888]`. Simulates noon daylight with correlated color temperature of 6504 K.
`"icc"`Profile Connection Space (PCS) illuminant used in ICC profiles. Approximation of `[0.9642, 1.000, 0.8249]` using fixed-point, signed, 32-bit numbers with 16 fractional bits. Actual value: ```[31595,32768, 27030]/32768```.

Data Types: `single` | `double` | `char`

## Output Arguments

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Converted XYZ color values, returned as a numeric array of the same shape and type as the input.

## Version History

Introduced in R2014b