@node Colour Spaces
@chapter Colour Spaces
@command{libclut} has a number of functions for converting
between colour space models. The supported colour space models
are [0, 1] sRGB, [0, 1] linear RGB, CIE xyY, CIE XYZ, and CIE Lab.
These functions are implemented as macros, but regular functions
are available either by putting the name in the function is
brackets, taking the address of the function, or by undefining
the macro with the name of the function.
@command{libclut} has two functions intended for internal use.
If the macro verions are used, their parameter must not have
any side-effets. Additionally their macro versions require
linking with @option{-lm}.
@table @code
@item double libclut_model_linear_to_standard1(double c)
Convert one component from [0, 1] linear RGB to [0, 1] sRGB.
@item double libclut_model_standard_to_linear1(double c)
Convert one component from [0, 1] sRGB to [0, 1] linear RGB.
@end table
@command{libclut} has ten functions that are intended for the
user to use, but some are used internally too. These functions'
parameters may have side-effects. All parameters are of the
type @code{double}, and they do not have a return value.
@table @code
@item libclut_model_linear_to_standard(*r. *g, *b)
Convert [0, 1] linear RGB to [0, 1] sRGB.
The macro variant requires linking with @option{-lm}, if
the @code{libclut_model_linear_to_standard1} is defined,
otherwise it requires linking with @option{-lclut}.
Parameters:
@table @code
@item r
Pointer to the linear red component, and output parameter
for the red component.
@item g
Pointer to the linear green component, and output parameter
for the green component.
@item b
Pointer to the linear blue component, and output parameter
for the blue component.
@end table
@item libclut_model_standard_to_linear(*r, *g, *b)
Convert [0, 1] sRGB to [0, 1] linear RGB.
The macro variant requires linking with @option{-lm}, if
the @code{libclut_model_standard_to_linear1} is defined,
otherwise it requires linking with @option{-lclut}.
Parameters:
@table @code
@item r
Pointer to the red component, and output parameter for the
linear red component.
@item g
Pointer to the green component, and output parameter for the
linear green component.
@item b
Pointer to the blue component, and output parameter for the
linear blue component.
@end table
@item libclut_model_ciexyy_to_ciexyz(x, y, Y, *X, *Z)
Convert CIE xyY to CIE XYZ.
Parameters:
@table @code
@item x
The x parameter.
@item y
The y parameter.
@item Y
The Y parameter. This is also the Y (middle) parameter
for the CIE XYZ colour.
@item X
Output parameter for the X parameter.
@item Z
Output parameter for the Z parameter.
@end table
@item libclut_model_ciexyz_to_ciexyy(X, Y, Z, *x, *y)
Convert CIE XYZ to CIE xyY.
Parameters:
@table @code
@item X
The X parameter.
@item Y
The Y parameter. This is also the Y (last) parameter
for the CIE xyY colour.
@item Z
The Z parameter.
@item x
Output parameter for the x parameter.
@item y
Output parameter for the y parameter.
@end table
@item libclut_model_ciexyz_to_linear(X, Y, Z, *r, *g, *b)
Convert CIE XYZ to [0, 1] linear RGB.
Parameters:
@table @code
@item X
The X parameter.
@item Y
The Y parameter.
@item Z
The Z parameter.
@item r
Output parameter for the red component.
@item g
Output parameter for the green component.
@item b
Output parameter for the blue component.
@end table
@item libclut_model_linear_to_ciexyz(r, g, b, *X, *Y, *Z)
Convert [0, 1] linear RGB to CIE XYZ.
Parameters:
@table @code
@item r
The red component.
@item g
The green component.
@item b
The blue component.
@item X
Output parameter for the X parameter.
@item Y
Output parameter for the Y parameter.
@item Z
Output parameter for the Z parameter.
@end table
@item libclut_model_srgb_to_ciexyy(r, g, b, *x, *y, *Y)
Convert [0, 1] linear RGB to CIE xyY.
The macro variant requires linking with @option{-lclut}
if any of @code{libclut_model_ciexyz_to_ciexyy},
@code{libclut_model_linear_to_ciexyz}, and
@code{libclut_model_standard_to_linear} are undefined.
The macro variant requires linking with @code{-lm} if
neither @code{libclut_model_standard_to_linear} nor
@code{libclut_model_standard_to_linear1} are undefined.
Parameters:
@table @code
@item r
The red component.
@item g
The green component.
@item b
The blue component.
@item x
Output parameter for the x parameter.
@item y
Output parameter for the y parameter.
@item Y
Output parameter for the Y parameter.
@end table
@item libclut_model_ciexyy_to_srgb(x, y, Y, *r, *g, *b)
Convert CIE xyY to [0, 1] sRGB.
The macro variant requires linking with @option{-lclut}
if any of @code{libclut_model_ciexyy_to_ciexyz},
@code{libclut_model_ciexyz_to_linear}, and
@code{libclut_model_linear_to_standard} are undefined.
The macro variant requires linking with @option{-lm} if
neither @code{libclut_model_linear_to_standard} nor
@code{libclut_model_linear_to_standard1} are undefined.
Parameters:
@table @code
@item x
The x parameter.
@item y
The y parameter.
@item Y
The Y parameter.
@item r
Output parameter for the red component.
@item g
Output parameter for the green component.
@item b
Output parameter for the blue component.
@end table
@item libclut_model_ciexyz_to_cielab(X, Y, Z, *L, *a, *b)
Convert from CIE XYZ to CIE L*a*b*.
The macro variant requires linking with @option{-lm}.
Parameters:
@table @code
@item X
The X parameter.
@item Y
The Y parameter.
@item Z
The Z parameter.
@item L
Output parameter for the L* component.
@item a
Output parameter for the a* component.
@item b
Output parameter for the b* component.
@end table
@item libclut_model_cielab_to_ciexyz(L, a, b, *X, *Y, *Z)
Convert from CIE L*a*b* to CIE XYZ.
Parameters:
@table @code
@item L
The L* component.
@item a
The a* component.
@item b
The b* component.
@item X
Output parameter for the X parameter.
@item Y
Output parameter for the Y parameter.
@item Z
Output parameter for the Z parameter.
@end table
@end table
