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@@ -3,7 +3,252 @@ NAME DESCRIPTION libcolour is C library for colour space conversions. + libcolour provides conversion between a large number of colour + spaces, including many different RGB colour spaces. It also + supports encode and non-encoded representations. libcolour + futhermore provides access to custom RGB colour spaces. -SEE ALSO - libclut(7) + To use libcolour, include the header file <libcolour.h> and + link with /usr/local/lib/libcolour.a -lm or -lcolour. +COLOUR MODELS + libcolour supports a number of colour models. A colour model + is specified with a value of + + typedef enum libcolour_model libcolour_model_t; + + The colour models can listed using the macros + + LIBCOLOUR_LIST_MODELS(IMACRO, TYPE_AFFIX) + + or + + LIBCOLOUR_LIST_MODELS_N(MACRO, TYPE_AFFIX, ...) + + where MACRO is the macro that shall be expanded, and + TYPE_AFFIX shall be f, lf, or llf for float-typed, + double-typed, and long double-typed colour module stuctures, + respectively. LIBCOLOUR_LIST_MODELS expands MACRO with three + parameters: enum libcolour_model value of the colour model, + typedef-name of struct used to store colours of the colour + model, and the name of the member in union libcolour_colour_f, + union libcolour_colour_lf, and union libcolour_colour_llf that + is used to store a colour with the colour model. + LIBCOLOUR_LIST_MODELS_N is identical to LIBCOLOUR_LIST_MODELS + except allows the programmer to specify additional parameters + to pass MACRO when it is expanded. + + There there are three structs defined for each colour model, + the first member in each struct is + + enum libcolour_model model; + + The three structs for each colour model are for different data + types: float, double, and long double. For example, for sRGB, + the follow structs are defined: + + typedef struct libcolour_srgb_f libcolour_srgb_f_t; + typedef struct libcolour_srgb_lf libcolour_srgb_lf_t; + typedef struct libcolour_srgb_llf libcolour_srgb_llf_t; + + for float, double, and long double, respectively. Similarly, + + typedef union libcolour_colour_f libcolour_colour_f_t; + typedef union libcolour_colour_lf libcolour_colour_lf_t; + typedef union libcolour_colour_llf libcolour_colour_llf_t; + + are used for float, double, long double, respectively, and all + have the member + + enum libcolour_model model; + + The structs are not padded to be of the same size. + + <libcolour.h> defines structs the following for colour models: + + Generic RGB + See LIBCOLOUR_RGB(7). + + Standard RGB + See LIBCOLOUR_SRGB(7). + + CIE xyY + See LIBCOLOUR_CIEXYY(7). + + CIE 1931 XYZ + See LIBCOLOUR_CIEXYZ(7). + + CIE L*a*b* + See LIBCOLOUR_CIELAB(7). + + CIE 1976 (L*, u*, v*) + See LIBCOLOUR_CIELUV(7). + + CIE LChuv (also known as CIE HLCuv) + See LIBCOLOUR_CIELCHUV(7). + + YIQ + See LIBCOLOUR_YIQ(7). + + YDbDr + See LIBCOLOUR_YDBDR(7). + + YUV + See LIBCOLOUR_YUV(7). + + YPBPR + See LIBCOLOUR_YPBPR(7). + + YCgCo + See LIBCOLOUR_YCGCO(7). + + CIE 1960 UCS + See LIBCOLOUR_CIE1960UCS(7). + + CIE 1964 (U*, V*, W*) + See LIBCOLOUR_CIEUVW(7). + +ILLUMINANTS + libcolour provides a number of initialiser macros for standard + illuminants. The following macros expand to a + libcolour_ciexyy_f_t with the standard 2 degrees observer + value in CIE xyY, each have a supplementary 10 degrees + observer counterpart using suffix _10DEG_OBS, both with the Y + value set to 1. Additionally, each macro, including the + _10DEG_OBS variants, have a variant that uses the _LF affix + that expands to a libcolour_ciexyy_lf_t and a variant that + uses the _LLF affix that expands to a libcolour_ciexyy_llf_t + in addition to the listed variants that uses the _F affix. + + LIBCOLOUR_ILLUMINANT_A_F + CIE Standard Illuminant A. + Incandescent/Tungsten. + 2855.54K (2848K in old definition of 1K). + + LIBCOLOUR_ILLUMINANT_B_F + CIE Standard Illuminant B. + Direct sunlight at noon (obsolete). + 4874K. + + LIBCOLOUR_ILLUMINANT_C_F + CIE Standard Illuminant C. + Average/north sky daylight (obsolete). + 6774K. + + LIBCOLOUR_ILLUMINANT_D50_F + CIE Standard Illuminant D50. + Horizon Light. + 5002.78K (5000K in old definition of 1K). + + LIBCOLOUR_ILLUMINANT_D55_F + CIE Standard Illuminant D55. + Mid-morning/mid-afternoon daylight. + 5503.06K (5500K in old definition of 1K). + + LIBCOLOUR_ILLUMINANT_D65_F + CIE Standard Illuminant D65. + Noon daylight. + 6503.62K (6500K in old definition of 1K). + + LIBCOLOUR_ILLUMINANT_D75_F + CIE Standard Illuminant D75. + North sky daylight. + 7504.17K (7500K in old definition of 1K). + + LIBCOLOUR_ILLUMINANT_E_F + CIE Standard Illuminant E. + Equal energy. + 5454K. + + LIBCOLOUR_ILLUMINANT_F1_F + CIE Standard Illuminant F1. + Daylight fluorescent. + 6430K. + + LIBCOLOUR_ILLUMINANT_F2_F + CIE Standard Illuminant F2. + Cool white fluorescent. + 4230K. + + LIBCOLOUR_ILLUMINANT_F3_F + CIE Standard Illuminant F3. + White fluorescent. + 3450K. + + LIBCOLOUR_ILLUMINANT_F4_F + CIE Standard Illuminant F4. + Warm white fluorescent. + 2940K. + + LIBCOLOUR_ILLUMINANT_F5_F + CIE Standard Illuminant F5. + Daylight fluorescent. + 6350K. + + LIBCOLOUR_ILLUMINANT_F6_F + CIE Standard Illuminant F6. + Lite white fluorescent. + 4150K. + + LIBCOLOUR_ILLUMINANT_F7_F + CIE Standard Illuminant F7. + D65 simulator, daylight simulator. + 6500K. + + LIBCOLOUR_ILLUMINANT_F8_F + CIE Standard Illuminant F8. + D50 simulator, Sylvania F40 Design 50. + 5000K. + + LIBCOLOUR_ILLUMINANT_F9_F + CIE Standard Illuminant F9. + Cool white deluxe fluorescent. + 4150K. + + LIBCOLOUR_ILLUMINANT_F10_F + CIE Standard Illuminant F10. + Philips TL85, Ultralume 50. + 5000K. + + LIBCOLOUR_ILLUMINANT_F11_F + CIE Standard Illuminant F11. + Philips TL84, Ultralume 40. + 4000K. + + LIBCOLOUR_ILLUMINANT_F12_F + CIE Standard Illuminant F12. + Philips TL83, Ultralume 30. + 3000K. + +FUNCTIONS + libcolour_convert(3) + Colour space and colour model conversion. + + libcolour_srgb_encode(3) + Apply the sRGB transfer function. + + libcolour_srgb_decode(3) + Unapply the sRGB transfer function. + + libcolour_delta_e(3) + Calculate delta E*_ab distance. + + libcolour_proper(3) + Sets any member or submember that may be incorrectly + set. + + libcolour_get_rgb_colour_space(3) + Selects RGB colour space. + + libcolour_marshal(3) + Marshal a colour record. + + libcolour_unmarshal(3) + Unmarshal a colour record. + +NOTES + All enum values have a macro with the same name defined which + can be used to test the existance of value. + +AUTHORS + Mattias Andrée <maandree@kth.se> |