colour.models.hdr_ipt Module

hdr-IPT Colourspace

Defines the hdr-IPT colourspace transformations:

See also

hdr-IPT Colourspace Jupyter Notebook

References

[1]Fairchild, M. D., & Wyble, D. R. (2010). hdr-CIELAB and hdr-IPT: Simple Models for Describing the Color of High-Dynamic-Range and Wide-Color-Gamut Images. In Proc. of Color and Imaging Conference (pp. 322–326). ISBN:9781629932156
colour.models.hdr_ipt.XYZ_to_hdr_IPT(XYZ, Y_s=0.2, Y_abs=100)[source]

Converts from CIE XYZ tristimulus values to hdr-IPT colourspace.

Parameters:
  • XYZ (array_like) – CIE XYZ tristimulus values.
  • Y_s (numeric or array_like) – Relative luminance \(Y_s\) of the surround in domain [0, 1].
  • Y_abs (numeric or array_like) – Absolute luminance \(Y_{abs}\) of the scene diffuse white in \(cd/m^2\).
Returns:

hdr-IPT colourspace array.
Return type:

ndarray

Notes

  • Input CIE XYZ tristimulus values needs to be adapted for CIE Standard Illuminant D Series D65.

Examples

>>> XYZ = np.array([0.96907232, 1.00000000, 1.12179215])
>>> XYZ_to_hdr_IPT(XYZ)  
array([ 94.6592917...,   0.3804177...,  -0.2673118...])
colour.models.hdr_ipt.hdr_IPT_to_XYZ(IPT_hdr, Y_s=0.2, Y_abs=100)[source]

Converts from hdr-IPT colourspace to CIE XYZ tristimulus values.

Parameters:
  • IPT_hdr (array_like) – hdr-IPT colourspace array.
  • Y_s (numeric or array_like) – Relative luminance \(Y_s\) of the surround in domain [0, 1].
  • Y_abs (numeric or array_like) – Absolute luminance \(Y_{abs}\) of the scene diffuse white in \(cd/m^2\).
Returns:

CIE XYZ tristimulus values.
Return type:

ndarray

Examples

>>> IPT_hdr = np.array([94.65929175, 0.38041773, -0.26731187])
>>> hdr_IPT_to_XYZ(IPT_hdr)  
array([ 0.9690723...,  1.        ,  1.1217921...])
colour.models.hdr_ipt.exponent_hdr_IPT(Y_s, Y_abs)[source]

Computes hdr-IPT colourspace Lightness \(\epsilon\) exponent.

Parameters:
  • Y_s (numeric or array_like) – Relative luminance \(Y_s\) of the surround in range [0, 1].
  • Y_abs (numeric or array_like) – Absolute luminance \(Y_{abs}\) of the scene diffuse white in \(cd/m^2\).
Returns:

hdr-IPT colourspace Lightness \(\epsilon\) exponent.
Return type:

array_like

Examples

>>> exponent_hdr_IPT(0.2, 100)  
1.6891383...