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Diffstat (limited to '')
| -rw-r--r-- | libred.h | 76 |
1 files changed, 76 insertions, 0 deletions
@@ -212,6 +212,82 @@ int libred_check_timetravel(void); */ int libred_get_colour(long int, double *, double *, double *); +/** + * Get the CIE xy values of a colour temperature + * + * libred has a table of colour temperature values, this + * function interpolates values that are missing. If you + * don't want any interpolation the `temp` parameter can + * be specified in one of the following ways: + * + * - floor: + * (temp - LIBRED_LOWEST_TEMPERATURE) / + * LIBRED_DELTA_TEMPERATURE * + * LIBRED_DELTA_TEMPERATURE + + * LIBRED_LOWEST_TEMPERATURE + * + * - ceiling: + * (temp - LIBRED_LOWEST_TEMPERATURE + + * LIBRED_DELTA_TEMPERATURE - 1) / + * LIBRED_DELTA_TEMPERATURE * + * LIBRED_DELTA_TEMPERATURE + + * LIBRED_LOWEST_TEMPERATURE + * + * - round to nearest: + * (temp - LIBRED_LOWEST_TEMPERATURE + + * LIBRED_DELTA_TEMPERATURE / 2) / + * LIBRED_DELTA_TEMPERATURE * + * LIBRED_DELTA_TEMPERATURE + + * LIBRED_LOWEST_TEMPERATURE + * + * @param temp The desired colour temperature + * @param x Output parameter for the x value + * @param y Output parameter for the y value + * @return 0 on succeess, -1 on error + * + * @throws EDOM The selected temperature is below 1000K + */ +int libred_get_colour_xy(long int, double *, double *); + +/** + * Calculate the colour temperature from its CIE xy values + * + * @param x The CIE x value for the colour temperature + * @param y The CIE y value for the colour temperature + * @param x_error Output parameter for the absolute error in + * the CIE x value of the returned colour + * temperature; may be `NULL` + * @param y_error Output parameter for the absolute error in + * the CIE y value of the returned colour + * temperature; may be `NULL` + * @return The closest matching colour temperature + */ +double libred_get_temperature_xy(double, double, double *, double *); + +/** + * Calculate the colour temperature from its [0, 1] sRGB values + * + * @param r The sRGB “red” value for the colour temperature + * @param g The sRGB green value for the colour temperature + * @param b The sRGB blue value for the colour temperature + * @param y Output parameter for the CIE Y value for the + * provided sRGB colour, the sRGB error values must + * be multiplied by this value to correct them to + * match the brightness of the input sRGB colour; + * may be `NULL` + * @param r_error Output parameter for the absolute error in the + * “red” value of the returned colour temperature; + * may be `NULL` + * @param g_error Output parameter for the absolute error in the + * green value of the returned colour temperature; + * may be `NULL` + * @param b_error Output parameter for the absolute error in the + * blue value of the returned colour temperature; + * may be `NULL` + * @return The closest matching colour temperature + */ +double libred_get_temperature(double, double, double, double *, double *, double *, double *); + #endif |