ZtoRGBpy

Version 1.0.1 Documentation

ZtoRGBpy.RGBColorProfile

class RGBColorProfile(weights=(2126.0, 7152.0, 722.0), gamma=0.5)[source]

Defines a color profile in a given RGB color space by conversion factors for red, green and blue to the Y component of the XYZ color space, i.e. the white point.

Parameters:
  • weights (tuple [ float, float, float ], optional, default: (2126.0, 7152.0, 772.0)) – Color component weight triple (\(W_R, W_G, W_B\)) for conversion to the XYZ color space Defaults to the sRGB color space defined by IEC[2].
  • gamma (float, optional, defaults: 0.5) – Gamma (\(\gamma\)) correction.
apply_gamma(rgb)[source]

Applies gamma correction to color

Parameters:rgb (array_like […]) – non-gamma corrected RGB color values
Returns:RGB (array [ rgb.shape ]) – gamma corrected RGB color values

Notes

Equivalent to \({RGB} = {rgb}^{\gamma}\)

get_chroma_limit()[source]

Return the limiting chroma

Returns:chroma_limit (float) – Limiting Chroma for the colorspace

Notes

The limiting chroma is computed from the transformation matrix as described in Fletcher 2019[1].

get_limits()[source]

Returns \(U_{max}\) and \(V_{max}\)

Returns:
  • Vmax (float) – V channel magnitude limit (\(V_{max}\))
  • Umax (float) – U channel magnitude limit (\(U_{max}\))

Notes

\(U_{max}\) and \(V_{max}\) represent the limits of the UV color space, as defined by[1]:

\[\begin{split}V_{max} =& \frac{\sqrt[3]{K_R}}{\sqrt[3]{K_R} + \sqrt[3]{K_B}}\\ U_{max} =& \frac{\sqrt[3]{K_B}}{\sqrt[3]{K_R} + \sqrt[3]{K_B}}\end{split}\]
get_ratios()[source]

Returns the relative ratios for red and blue

Returns:
  • red_ratio (float) – Relative ratio of red (\(K_R\))
  • blue_ratio (float) – Relative ratio of blue (\(K_B\))

Notes

Ratios for red (\(K_R\)) and blue (\(K_B\)) are defined by:

\[\begin{split}K_R =& \frac{W_R}{W_R + W_G + W_B}\\ K_B =& \frac{W_B}{W_R + W_G + W_B}\end{split}\]
get_transform()[source]

Returns the UV to RGB transformation matrix \(\mathbf{K_Q}\).

Returns:transformation (array [3, 2, dtype = float]) – transformation matrix \(\mathbf{K_Q}\)

Notes

The transformation matrix \(\mathbf{K_Q}\) is defined by[1]:

\[\begin{split}\mathbf{K_Q} &= \left[\begin{matrix} 0 & \frac{1-K_R}{V_{max}} \\ \frac{K_B\left( 1-K_B \right)}{U_{max}\left( K_B+K_R-1 \right)} & \frac{K_R\left( 1-K_R \right)}{V_{max}\left( K_B+K_R-1 \right)}\\ \frac{1-K_B}{U_{max}} & 0 \\ \end{matrix}\right]\end{split}\]
remove_gamma(RGB)[source]

Removes gamma correction from color

Parameters:RGB (array_like […]) – gamma corrected RGB color values
Returns:rgb (array [ RGB.shape ]) – non-gamma corrected RGB color values

Notes

Equivalent to \({rgb} = {RGB}^{\frac{1}{\gamma}}\)

Predefined Color Profiles

sRGB_LOW Defines a color profile in a given RGB color space by conversion factors for red, green and blue to the Y component of the XYZ color space, i.e.
sRGB_HIGH Defines a color profile in a given RGB color space by conversion factors for red, green and blue to the Y component of the XYZ color space, i.e.
sRGB Defines a color profile in a given RGB color space by conversion factors for red, green and blue to the Y component of the XYZ color space, i.e.

[1](1, 2, 3) Glen Fletcher. A Perceptually Uniform RGB Subset for Representing Complex-valued Data. Technical Report, University of Technology Sydney, 2019. URL: https://glenfletcher.com/research/a-perceptually-uniform-rgb-subset-for-representing-complex-valued-data/.
[2]International Electrotechnical Commission. Colour Measurement and Management in Multimedia Systems and Equipment. 1998. URL: http://www2.units.it/ipl/students_area/imm2/files/Colore1/sRGB.pdf.

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