diff options
Diffstat (limited to '')
| -rw-r--r-- | doc/info/chap/clut-manipulation.texinfo | 4 | ||||
| -rw-r--r-- | doc/info/chap/colour-spaces.texinfo | 351 | ||||
| -rw-r--r-- | doc/info/chap/overview.texinfo | 4 |
3 files changed, 355 insertions, 4 deletions
diff --git a/doc/info/chap/clut-manipulation.texinfo b/doc/info/chap/clut-manipulation.texinfo index 477e107..99fc0f0 100644 --- a/doc/info/chap/clut-manipulation.texinfo +++ b/doc/info/chap/clut-manipulation.texinfo @@ -10,8 +10,8 @@ colour lookup table that shall be manipulated. Pointer to the gamma ramps. This must be a pointer to an instance of a @code{struct} that must at least have the array members @code{red}, @code{green}, and -@code{blue}, whose elements shall be of the time -specified by the parameter @code{type}. The struct +@code{blue}, whose elements shall be of the type +specified by the parameter @code{type}. The @code{struct} must also have the scalar members @code{red_size}, @code{green_size}, and @code{blue_size}, and shall be of the type @code{size_t}; they shall specify the diff --git a/doc/info/chap/colour-spaces.texinfo b/doc/info/chap/colour-spaces.texinfo index 86662c6..7b9d751 100644 --- a/doc/info/chap/colour-spaces.texinfo +++ b/doc/info/chap/colour-spaces.texinfo @@ -1,6 +1,11 @@ @node Colour Spaces @chapter Colour Spaces +@menu +* RGB Conversion:: RGB colour space conversion functions. +@end menu + + @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. @@ -245,3 +250,349 @@ Output parameter for the Z parameter. @end table @end table + +@node RGB Conversion +@section RGB Conversion + +@command{libclut} provides a functions for converting +RGB values between RGB colour spaces. An RGB colour space +is described using @code{struct libclut_rgb_colour_space} +(also known as @code{libclut_rgb_colour_space_t}). It +describes the colour of the red, green, and blue, +stimuli as well as the white point, in CIE xyY. It does +however not describe the colour space's gamma function, +because sRGB uses a irregular gamma function, and +ECI@tie{}RGB@tie{}v2 uses L*. The structure contains +the following @code{double}:s: + +@table @code +@item red_x +The CIE xyY x-value of the red stimulus. +@item red_y +The CIE xyY y-value of the red stimulus. +@item red_Y +The CIE xyY Y-value of the red stimulus. +@item green_x +The CIE xyY x-value of the green stimulus. +@item green_y +The CIE xyY y-value of the green stimulus. +@item green_Y +The CIE xyY Y-value of the green stimulus. +@item blue_x +The CIE xyY x-value of the blue stimulus. +@item blue_y +The CIE xyY y-value of the blue stimulus. +@item blue_Y +The CIE xyY Y-value of the blue stimulus. +@item white_x +The CIE xyY x-value of the white point. +@item white_y +The CIE xyY y-value of the white point. +@item white_Y +The CIE xyY Y-value of the white point. +@end table + +@code{libclut} provides macros used to initialise a +@code{struct libclut_rgb_colour_space} with values +for a number of RGB colour spaces. These are listed +below, along with the gamma each colour space uses. + +@multitable {PAL/SECAM RGB} {@b{Gamma}} {@code{LIBCLUT_RGB_COLOUR_SPACE_WIDE_GAMUT_RGB_INITIALISER}} +@item +@b{Model} +@tab +@b{Gamma} +@tab +@b{Initialiser} +@item +sRGB +@tab +sRGB +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_SRGB_INITIALISER} +@item +Adobe RGB (1998) +@tab +2.2 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_ADOBE_RGB_INITIALISER} +@item +Apple RGB +@tab +1.8 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_APPLE_RGB_INITIALISER} +@item +Best RGB +@tab +2.2 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_BEST_RGB_INITIALISER} +@item +Beta RGB +@tab +2.2 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_BETA_RGB_INITIALISER} +@item +Bruce RGB +@tab +2.2 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_BRUCE_RGB_INITIALISER} +@item +CIE RGB +@tab +2.2 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_CIE_RGB_INITIALISER} +@item +ColorMatch RGB +@tab +1.8 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_COLORMATCH_RGB_INITIALISER} +@item +Don RGB 4 +@tab +2.2 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_DON_RGB_4_INITIALISER} +@item +ECI RGB v2 +@tab +L* +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_ECI_RGB_V2_INITIALISER} +@item +Ekta Space PS5 +@tab +2.2 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_EKTA_SPACE_PS5_INITIALISER} +@item +NTSC RGB +@tab +2.2 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_NTSC_RGB_INITIALISER} +@item +PAL/SECAM RGB +@tab +2.2 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_PAL_SECAM_RGB_INITIALISER} +@item +ProPhoto RGB +@tab +1.8 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_PROPHOTO_RGB_INITIALISER} +@item +SMPTE-C RGB +@tab +2.2 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_SMPTE_C_RGB_INITIALISER} +@item +Wide Gamut RGB +@tab +2.2 +@tab +@code{LIBCLUT_RGB_COLOUR_SPACE_WIDE_GAMUT_RGB_INITIALISER} +@end multitable + +To create a description for the sRGB colour space write: + +@example +struct libclut_rgb_colour_space srgb = \ + LIBCLUT_RGB_COLOUR_SPACE_SRGB_INITIALISER; +@end example + +@command{libgamma} and @command{libcoopgamma} can be used +to get the x and y values of the user's monitors' red, +green, and blue stimuli. Otherwise, all values specified +by @code{LIBCLUT_RGB_COLOUR_SPACE_SRGB_INITIALISER} can +be used, and the sRGB gamma function can be used. However, +the Y values of the stimuli may be off, however, this does +not affect conversion. + +sRGB uses an irregular gamma function. @command{libclut} +assumes that the colour spaces uses this gamma function +when converting between RGB colour spaces. If you want to +convert from a colour space with another gamma function, +you must first convert the gamma function. This can be +done by linearising the values and then use +@code{libclut_model_linear_to_standard1}, +@code{libclut_model_linear_to_standard}, or +@code{libclut_standardise}. If you want to convert to a +colour spce with another gamma function, you must after +the conversion also convert the gamma function. This can +be done by using @code{libclut_model_standard_to_linear1}, +@code{libclut_model_standard_to_linear}, or +@code{libclut_linearise}, and then converting from linear +to the proper gamma function. Note that even if you are +converting between two colour spaces with the same gamma +function, gamma function conversion must be done (before +and after) unless they use the sRGB gamma function. + +Before RGB colour space conversion can be done, you need +to create a conversion matrix. It has the type + +@example +typedef double libclut_colour_space_conversion_matrix_t[3][3]; +@end example + +@noindent +and can be created with +@table @code +@item int libclut_model_get_rgb_conversion_matrix(*from, *to, M, Minv) +Create a conversion matrix from one RGB colour space to another +RGB colour space, and optionally a matrix for an inverse conversion. + +Returns 0 on success, and -1 on error. The only possible error is +@code{EINVAL}, which indicates that there is something wrong with +the colour spaces and a conversion matrix cannot be created. + +This function is not available as a macro, thus, linking with +@code{-lclut} is required. + +Parameters: +@table @code +@item const libclut_rgb_colour_space_t* from +Description of the input colour space. +@item const libclut_rgb_colour_space_t* to +Description of the output colour space. +@item libclut_colour_space_conversion_matrix_t M +Matrix to fill with values so it can be used for +converting from the input colour space to the +output colour space. +@item libclut_colour_space_conversion_matrix_t Minv +Matrix to fill with values so it can be used for +converting from the output colour space to the +input colour space. (That is, inverse conversion.) +This parameter may be @code{NULL}. +@end table +@end table + +You can also create the matrix manually. If you for example +have a @code{libclut_colour_space_conversion_matrix_t} named +@code{M}, and want to set the cell at row 1 and column 3, to +0.5, you make the assignment @code{M[0][2] = 0.5}. + +Once you have your conversion matrix, @command{libclut} has +three macro functions you can used to convert colours between +RGB colour space. Remember that they require the sRGB gamma +function. + +@table @code +@item libclut_model_convert_rgb(r, g, b, M, *out_r, *out_g, *out_b) +Convert a single RGB colour into another RGB colour space. +The colour space must have same gamma functions as RGB. + +This macro is also available a function. If the function is +used, linking with @code{-lclut} is required, otherwise, +linking with @code{-lm} is required, or @code{-lclut} if +@code{libclut_model_standard_to_linear1} or +@code{libclut_model_linear_to_standard1} is undefined. + +Parameters: +@table @code +@item double r +The red value of the colour to convert. +@item double g +The green value of the colour to convert. +@item double b +The blue value of the colour to convert. +@item libclut_colour_space_conversion_matrix_t M +The conversion matrix. +@item double* out_r +Output parameter for the red value of the colour after conversion. +@item double* out_g +Output parameter for the green value of the colour after conversion. +@item double* out_b +Output parameter for the blue value of the colour after conversion. +@end table + +@item libclut_convert_rgb_inplace(clut, max, type, m, trunc) +Convert the curves between two RGB colour spaces. + +The red, green, and blue ramps must be of the same size. + +None of the parameter may have side-effects. + +Requires linking with @code{-lm}, or @code{-lclut} if +@code{libclut_model_standard_to_linear1}, +@code{libclut_model_linear_to_standard1}, or +@code{libclut_model_convert_rgb} is undefined. + +Parameters: +@table @code +@item clut +Pointer to the gamma ramps to convert. This must be a pointer to +an instance of a struct that must at least have the array members +@code{red}, @code{green}, and @code{blue}, whose elements shall be +of the type specified by the parameter @code{type}. The @code{struct} +must also have the scalar members @code{red_size}, @code{green_size}, +and @code{blue_size}, and shall be of the type @code{size_t}; they +shall specify the number of stops (elements) in the arrays @code{.red}, +@code{.green}, and @code{.blue}, respectively, which shall be the +gamma ramp for the red, green, and blue channels respectively. Its +values will be modified to the new values. +@item max +The maximum value on each stop in the ramps. +@item type +The data type used for each stop in the ramps. +@item libclut_colour_space_conversion_matrix_t m +Conversion matrix. +@item int trunc +If this is a non-zero value, resulting colours that are +out of gamut are truncated. (Not necessarily the best +approximation.) +@end table + +@item libclut_convert_rgb(clut, max, type, m, trunc, out) +Convert the curves between two RGB colour spaces. + +This is a slower version of @code{libclut_convert_rgb_inplace} +that supports clut:s where the red, green, and blue ramps +are not of the same size. + +None of the parameter may have side-effects. + +Requires linking with @code{-lm}. If +@code{libclut_model_linear_to_standard1}, +@code{libclut_model_standard_to_linear1}, or +@code{libclut_model_convert_rgb} has been undefined, +linking with @code{-lclut} is also required. + +Parameters: +@table @code +@item clut +Pointer to the gamma ramps to convert. This must be a pointer to +an instance of a struct that must at least have the array members +@code{red}, @code{green}, and @code{blue}, whose elements shall be +of the type specified by the parameter @code{type}. The @code{struct} +must also have the scalar members @code{red_size}, @code{green_size}, +and @code{blue_size}, and shall be of the type @code{size_t}; they +shall specify the number of stops (elements) in the arrays @code{.red}, +@code{.green}, and @code{.blue}, respectively, which shall be the +gamma ramp for the red, green, and blue channels respectively. Its +values are not modified. +@item max +The maximum value on each stop in the ramps. +@item type +The data type used for each stop in the ramps. +@item libclut_colour_space_conversion_matrix_t m +Conversion matrix. +@item int trunc +If this is a non-zero value, resulting colours that are +out of gamut are truncated. (Not necessarily the best +approximation.) +@item clut +Pointer to the gamma ramps of the output values. Shall be of +the same data type as @code{clut}. And have the same values on +@code{.red_size}, @code{.green_size}, and @code{.blue_size} as +@code{clut}. +@end table +@end table diff --git a/doc/info/chap/overview.texinfo b/doc/info/chap/overview.texinfo index b2234bf..65a2b76 100644 --- a/doc/info/chap/overview.texinfo +++ b/doc/info/chap/overview.texinfo @@ -7,7 +7,7 @@ the header @file{<libclut.h>}. Some functionality also requires that the objects be linked with @option{-lclut}. @command{libclut} is designed to work well with -@command{libgamma} @command{libcoopgamma}, but does not -require that either is used for any of its +@command{libgamma} and @command{libcoopgamma}, but does +not require that either is used for any of its [@command{libclut}'s] functionality. |