diff options
| -rw-r--r-- | Makefile | 6 | ||||
| -rw-r--r-- | blackbody.c | 170 | ||||
| -rw-r--r-- | generate-table.c | 2 | ||||
| -rw-r--r-- | libred.7 | 3 | ||||
| -rw-r--r-- | libred.h | 30 | ||||
| -rw-r--r-- | libred.h.0 | 21 | ||||
| -rw-r--r-- | libred_get_colour.3 | 8 | ||||
| -rw-r--r-- | libred_get_temperature.3 | 89 | ||||
| l--------- | libred_get_temperature_xy.3 | 1 | ||||
| -rw-r--r-- | libred_solar_elevation.3 | 3 |
10 files changed, 230 insertions, 103 deletions
@@ -27,6 +27,8 @@ MAN7 = libred.7 MAN3 =\ libred_get_colour.3\ libred_get_colour_xy.3\ + libred_get_temperature.3\ + libred_get_temperature_xy.3\ libred_solar_elevation.3 @@ -36,7 +38,9 @@ blackbody.o: 10deg-xy.i 10deg-rgb.i libred.h generate-table.o: blackbody.c 10deg-xy.i libred.h 10deg-xy.i: 10deg - sed -e 's/^/{/' -e 's/ /, /' -e 's/$$/},/' < 10deg | sed '$$s/,$$//' > $@ + sed '56s/^.*$$/0.312727 0.329023/' < 10deg |\ + sed -e 's/^/{/' -e 's/ /, /' -e 's/$$/},/' | \ + sed '$$s/,$$//' > $@ 10deg-rgb.i: generate-table 10deg ./generate-table > $@ diff --git a/blackbody.c b/blackbody.c index 78608c1..1abf133 100644 --- a/blackbody.c +++ b/blackbody.c @@ -11,6 +11,7 @@ # include <stddef.h> + /** * Colour temperatures in CIE xy (xyY without Y) */ @@ -26,6 +27,7 @@ static struct rgb {double r, g, b;} rgb_table[] = { }; + #endif /** * Convert from CIE xyY to [0, 1] sRGB @@ -41,9 +43,16 @@ static struct rgb {double r, g, b;} rgb_table[] = { static void ciexyy_to_srgb(double x, double y, double Y, double *r, double *g, double *b) { -#define SRGB(C) (((C) <= 0.0031308) ? (12.92 * (C)) : ((1.0 + 0.055) * pow((C), 1.0 / 2.4) - 0.055)) +#define LINEAR_TO_SRGB(C)\ + do {\ + double sign = (C) < 0 ? -1 : 1;\ + (C) *= sign;\ + (C) = (((C) <= 0.0031306684425217108) ? (12.92 * (C)) : (1.055 * pow((C), 1.0 / 2.4) - 0.055));\ + (C) *= sign;\ + } while (0) + double X, Z, max; - + #if __GNUC__ # pragma GCC diagnostic push # pragma GCC diagnostic ignored "-Wfloat-equal" @@ -55,13 +64,16 @@ ciexyy_to_srgb(double x, double y, double Y, double *r, double *g, double *b) # pragma GCC diagnostic pop #endif - /* Convert CIE XYZ to [0, 1] linear RGB (ciexyz_to_linear) */ - *r = ( 3.240450 * X) + (-1.537140 * Y) + (-0.4985320 * Z); - *g = (-0.969266 * X) + ( 1.876010 * Y) + ( 0.0415561 * Z); - *b = (0.0556434 * X) + (-0.204026 * Y) + ( 1.0572300 * Z); - - /* Convert [0, 1] linear RGB to [0, 1] sRGB */ - SRGB(*r), SRGB(*g), SRGB(*b); + /* Convert CIE XYZ to [0, 1] linear RGB */ + *r = ( 3.24044625464773750067593027779366821050643920898438 * X) + + (-1.53713476182008057513428411766653880476951599121094 * Y) + + (-0.49853019302272871815517873983480967581272125244141 * Z); + *g = (-0.96926660624467975146956177923129871487617492675781 * X) + + ( 1.87601195978837020916785149893257766962051391601562 * Y) + + ( 0.04155604221443006535130493261931405868381261825562 * Z); + *b = ( 0.05564350356435283223577314970498264301568269729614 * X) + + (-0.20402617973596023914772956686647376045584678649902 * Y) + + ( 1.05722656772270329206264705135254189372062683105469 * Z); /* Adjust colours for use */ max = fmax(fmax(fabs(*r), fabs(*g)), fabs(*b)); @@ -76,35 +88,66 @@ ciexyy_to_srgb(double x, double y, double Y, double *r, double *g, double *b) *r = *r > 0.0 ? *r : 0.0; *g = *g > 0.0 ? *g : 0.0; *b = *b > 0.0 ? *b : 0.0; + + /* Convert [0, 1] linear RGB to [0, 1] sRGB */ + LINEAR_TO_SRGB(*r); + LINEAR_TO_SRGB(*g); + LINEAR_TO_SRGB(*b); } #ifndef LIBRED_COMPILING_PARSER + /** - * Perform linear interpolation (considered very good) - * between the CIE xy values for two colour temperatures - * and convert the result to sRGB. The two colours should - * be the closest below the desired colour temperature, - * and the closest above the desired colour temperature + * Convert from [0, 1] sRGB to CIE xyY * - * @param x1 The 'x' component for the low colour - * @param y1 The 'y' component for the low colour - * @param x2 The 'x' component for the high colour - * @param y2 The 'y' component for the high colour - * @param temp The desired colour temperature - * @param r Output parameter for the “red” value - * @param g Output parameter for the green value - * @param b Output parameter for the blue value + * @param r The “red” value + * (Seriously, sRGB red is orange, just look at it fullscreen) + * @param g The green value + * @param b The blue value + * @param x Output parameter for The 'x' component + * @param y Output parameter for The 'y' component + * @param Y Output parameter for The 'Y' component */ static void -interpolate(double x1, double y1, double x2, double y2, double temp, double *r, double *g, double *b) +srgb_to_ciexyy(double r, double g, double b, double *x, double *y, double *Y) { - double weight = fmod(temp - (LIBRED_LOWEST_TEMPERATURE % LIBRED_DELTA_TEMPERATURE), - (double)LIBRED_DELTA_TEMPERATURE) / (double)LIBRED_DELTA_TEMPERATURE; - double x = x1 * (1 - weight) + x2 * weight; - double y = y1 * (1 - weight) + y2 * weight; - ciexyy_to_srgb(x, y, 1.0, r, g, b); +#define SRGB_TO_LINEAR(C)\ + do {\ + double sign = (C) < 0 ? -1 : 1;\ + (C) *= sign;\ + (C) = (((C) <= 0.0031306684425217108 * 12.92) ? ((C) / 12.92) : pow(((C) + 0.055) / 1.055, 2.4));\ + (C) *= sign;\ + } while (0) + + /* Convert [0, 1] sRGB to [0, 1] linear RGB */ + double s, z; + + SRGB_TO_LINEAR(r); + SRGB_TO_LINEAR(g); + SRGB_TO_LINEAR(b); + + /* Convert [0, 1] linear RGB to CIE XYZ */ + *x = 0.41245744558236757670854899515688885003328323364258 * r + + 0.35757586524551587814357844763435423374176025390625 * g + + 0.18043724782639966597308500695362454280257225036621 * b; + *y = 0.21267337037840827740353688568575307726860046386719 * r + + 0.71515173049103175628715689526870846748352050781250 * g + + 0.07217489913055986916479156434434116818010807037354 * b; + z = 0.01933394276167346020889326041469757910817861557007 * r + + 0.11919195508183859366635459764438564889132976531982 * g + + 0.95030283855237174250873977143783122301101684570312 * b; + *Y = z; + + /* Convert CIE XYZ to CIE xyY */ + *Y = *y; + s = *x + *y + z; + *x /= s; + *y /= s; + if (!isfinite(*x) || !isfinite(*y)) + *x = *y = 0; } + /** * Perform linear interpolation (considered very good) * between the CIE xy values for two colour temperatures. @@ -121,7 +164,7 @@ interpolate(double x1, double y1, double x2, double y2, double temp, double *r, * @param y Output parameter for the CIE y value */ static void -interpolate_xy(double x1, double y1, double x2, double y2, double temp, double *x, double *y) +interpolate(double x1, double y1, double x2, double y2, double temp, double *x, double *y) { double weight = fmod(temp - (LIBRED_LOWEST_TEMPERATURE % LIBRED_DELTA_TEMPERATURE), (double)LIBRED_DELTA_TEMPERATURE) / (double)LIBRED_DELTA_TEMPERATURE; @@ -129,8 +172,9 @@ interpolate_xy(double x1, double y1, double x2, double y2, double temp, double * *y = y1 * (1 - weight) + y2 * weight; } + int -libred_get_colour(long int temp, double *r, double *g, double *b) +libred_get_colour_xy(long int temp, double *x, double *y) { double x1, y1, x2, y2; size_t i; @@ -152,18 +196,18 @@ libred_get_colour(long int temp, double *r, double *g, double *b) y1 = xy_table[i].y; x2 = xy_table[i + 1].x; y2 = xy_table[i + 1].y; - interpolate(x1, y1, x2, y2, (double)temp, r, g, b); + interpolate(x1, y1, x2, y2, (double)temp, x, y); } else { - *r = rgb_table[i].r; - *g = rgb_table[i].g; - *b = rgb_table[i].b; + *x = xy_table[i].x; + *y = xy_table[i].y; } return 0; } + int -libred_get_colour_xy(long int temp, double *x, double *y) /* TODO test */ +libred_get_colour(long int temp, double *r, double *g, double *b) { double x1, y1, x2, y2; size_t i; @@ -181,25 +225,29 @@ libred_get_colour_xy(long int temp, double *x, double *y) /* TODO test */ i = (size_t)(tmp / LIBRED_DELTA_TEMPERATURE); if (tmp % LIBRED_DELTA_TEMPERATURE) { + double x, y; x1 = xy_table[i].x; y1 = xy_table[i].y; x2 = xy_table[i + 1].x; y2 = xy_table[i + 1].y; - interpolate_xy(x1, y1, x2, y2, (double)temp, x, y); + interpolate(x1, y1, x2, y2, (double)temp, &x, &y); + ciexyy_to_srgb(x, y, 1, r, g, b); } else { - *x = xy_table[i].x; - *y = xy_table[i].y; + *r = rgb_table[i].r; + *g = rgb_table[i].g; + *b = rgb_table[i].b; } return 0; } + double -libred_get_temperature_xy(double x, double y, double *x_error, double *y_error) /* TODO man, test */ +libred_get_temperature_xy(double x, double y, double *x_error, double *y_error) { - size_t i, j; + size_t i = 0, j; double x1, y1, x2, y2, dx, dy, xd, yd, t, d2; - double best_temp = 0, best_d2 = INFINITY; + double best_temp = -1, best_d2 = INFINITY; if (!x_error) x_error = &dx; @@ -232,55 +280,23 @@ libred_get_temperature_xy(double x, double y, double *x_error, double *y_error) t *= (double)(j - i); best_temp = (double)i + t; } + + i = j; } return best_temp * LIBRED_DELTA_TEMPERATURE + LIBRED_LOWEST_TEMPERATURE; } -/** - * Convert from [0, 1] sRGB to CIE xyY - * - * @param r The “red” value - * (Seriously, sRGB red is orange, just look at it fullscreen) - * @param g The green value - * @param b The blue value - * @param x Output parameter for The 'x' component - * @param y Output parameter for The 'y' component - * @param Y Output parameter for The 'Y' component - */ -static void -srgb_to_ciexyy(double r, double g, double b, double *x, double *y, double *Y) -{ - double s, z; - - r *= s = r < 0 ? -1 : 1; - r = s * (r <= 0.0031306684425217108 * 12.92 ? r * 12.92 : pow((r + 0.055) / 1.055, 2.4)); - g *= s = g < 0 ? -1 : 1; - g = s * (g <= 0.0031306684425217108 * 12.92 ? g * 12.92 : pow((g + 0.055) / 1.055, 2.4)); - b *= s = b < 0 ? -1 : 1; - b = s * (g <= 0.0031306684425217108 * 12.92 ? b * 12.92 : pow((b + 0.055) / 1.055, 2.4)); - - *x = (0.41245744558236758 * r) + (0.35757586524551588 * g) + (0.18043724782639967 * b); - *y = (0.21267337037840828 * r) + (0.71515173049103176 * g) + (0.07217489913055987 * b); - z = (0.01933394276167346 * r) + (0.11919195508183859 * g) + (0.95030283855237174 * b); - - *Y = *y; - s = *x + *y + z; - *x /= s; - *y /= s; - if (!isfinite(*x) || !isfinite(*y)) - *x = *y = 0; -} double -libred_get_temperature(double r, double g, double b, double *y, /* TODO man, test */ +libred_get_temperature(double r, double g, double b, double *y, double *r_error, double *g_error, double *b_error) { double tx, ty, luma, x_error, y_error, ret; srgb_to_ciexyy(r, g, b, &tx, &ty, &luma); ret = libred_get_temperature_xy(tx, ty, &x_error, &y_error); - ciexyy_to_srgb(x_error, y_error, luma, &r, &g, &b); + ciexyy_to_srgb(x_error, y_error, 1, &r, &g, &b); if (y) *y = luma; diff --git a/generate-table.c b/generate-table.c index c5c0ca3..a8cde38 100644 --- a/generate-table.c +++ b/generate-table.c @@ -18,7 +18,7 @@ static struct xy {double x, y;} xy_table[] = { #include "10deg-xy.i" }; -/* define ciexyy_to_srgb() and adjust_luma() */ +/* define ciexyy_to_srgb() */ #define LIBRED_COMPILING_PARSER #include "blackbody.c" @@ -7,6 +7,9 @@ is a C library for calculating the Sun's apparent elevation and colours temperatures. .SH SEE ALSO .BR libred.h (0), +.BR libred_get_colour (3), +.BR libred_get_temperature (3), +.BR libred_solar_elevation (3), .BR solar-python (7), .BR radharc (1), .BR redshift (1), @@ -250,21 +250,6 @@ int libred_get_colour(long int, double *, double *, double *); 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 @@ -288,6 +273,21 @@ double libred_get_temperature_xy(double, double, double *, double *); */ double libred_get_temperature(double, double, double, double *, double *, 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 *); + #endif @@ -8,7 +8,8 @@ libred.h \- Solar elevation and blackbody colour calculation .fi .PP Link with -.IR -lred . +.I -lred +.IR -lm . .SH DESCRIPTION The .I <libred.h> @@ -116,11 +117,21 @@ It is night only if the Sun's apparent elevation is negative. This header defines the following functions: .TP * -.BR libred_solar_elevation (3) +.BR libred_get_colour (3) .TP * -.BR libred_get_colour (3) +.BR libred_get_colour_xy (3) +.TP +* +.BR libred_get_temperature (3) +.TP +* +.BR libred_get_temperature (3) +.TP +* +.BR libred_solar_elevation (3) .SH SEE ALSO .BR libred (7), -.BR libred_solar_elevation (3), -.BR libred_get_colour (3) +.BR libred_get_colour (3), +.BR libred_get_temperature (3), +.BR libred_solar_elevation (3) diff --git a/libred_get_colour.3 b/libred_get_colour.3 index 61a62ff..d6649d2 100644 --- a/libred_get_colour.3 +++ b/libred_get_colour.3 @@ -1,6 +1,6 @@ .TH LIBRED_GET_COLOUR 3 LIBRED .SH NAME -libred_get_colour \- Calculate a colour temperature +libred_get_colour \- Calculate the colour of a temperature .SH SYNOPSIS .nf #include <libred.h> @@ -10,7 +10,8 @@ int \fBlibred_get_colour_xy\fP(long int \fItemp\fP, double *\fIx\fP, double *\fI .fi .PP Link with -.IR -lred . +.I -lred +.IR -lm . .SH DESCRIPTION .BR libred_get_colour () gets or interpolates the colour temperature for @@ -100,4 +101,5 @@ is less than .SH SEE ALSO .BR libred.h (0), .BR libred (7), -.BR libred_get_solar_elevation (3) +.BR libred_get_temperature (3), +.BR libred_solar_elevation (3) diff --git a/libred_get_temperature.3 b/libred_get_temperature.3 new file mode 100644 index 0000000..f5e8883 --- /dev/null +++ b/libred_get_temperature.3 @@ -0,0 +1,89 @@ +.TH LIBRED_GET_TEMPERATURE 3 LIBRED +.SH NAME +libred_get_temperature \- Calculate the temperature of a colour +.SH SYNOPSIS +.nf +#include <libred.h> + +double \fBlibred_get_temperature\fP(double \fIr\fP, double \fIg\fP, double \fIb\fP, double *\fIY\fP, + double *\fIr_error\fP, double *\fIg_error\fP, double *\fIb_error\fP); +double \fBlibred_get_temperature_xy\fP(double \fIx\fP, double \fIy\fP, double *\fIx_error\fP, double *\fIy_error\fP); +.fi +.PP +Link with +.I -lred +.IR -lm . +.SH DESCRIPTION +The +.BR libred_get_temperature () +function parses +.RI ( r , +.IR g , +.IR b ) +as a colour encoded in sRGB with values between 0 and 1 +and with the sRGB transfer function applied. From that +it calculates the CIE Y (luminosity) of the colour and +stores it in +.I *Y +and then normalises the the colour to have Y = 1 and +calculates the closest matching colour temperature, +which is returned. +.PP +The calculated temperature may not line perfectly with +the colour so the difference between the colour of the +returned temperature and the input colour (after +normalisation to Y = 1) is returned in sRGB as +.RI ( *r_error ", " *g_error ", " *b_error ), +interpreted the same way as +.IR r , +.IR g , +and +.IR b . +.PP +The +.BR libred_get_temperature_xy () +function is a variant of the +.BR libred_get_temperature () +function that uses the CIE xy colour space +(CIE xyY with Y = 1). Unlike sRGB, CIE xy +does not have a transfer function, so the values +are linear, and the values also do not have any +limits and does have a natural interpretation. +.PP +Any of +.IR Y , +.IR r_error , +.IR g_error , +.IR b_error , +.IR x_error , +and +.IR y_error +that is +.I NULL +is ignored. +.SH RETURN VALUE +The +.BR libred_get_temperature () +and +.BR libred_get_temperature_xy () +functions return the colour temperature in Kelvins. +.SH ERRORS +None. +.SH NOTES +The sRGB transfer function is applied to +.IR *r_error , +.IR *g_error , +and +.IR *b_error . +One cannoy simply subtract them from +.IR r , +.IR g , +and +.IR b , +without first undoing the transfer function, +to get the colour or the calculated temperature. +.SH SEE ALSO +.BR libred.h (0), +.BR libred (7), +.BR libred_get_temperature (3), +.BR libred_solar_elevation (3) diff --git a/libred_get_temperature_xy.3 b/libred_get_temperature_xy.3 new file mode 120000 index 0000000..b7a4244 --- /dev/null +++ b/libred_get_temperature_xy.3 @@ -0,0 +1 @@ +libred_get_temperature.3
\ No newline at end of file diff --git a/libred_solar_elevation.3 b/libred_solar_elevation.3 index 70587ca..f72f8e5 100644 --- a/libred_solar_elevation.3 +++ b/libred_solar_elevation.3 @@ -9,7 +9,8 @@ int \fBlibred_solar_elevation\fP(double \fIlatitude\fP, double \fIlongitude\fP, .fi .PP Link with -.IR -lred . +.I -lred +.IR -lm . .SH DESCRIPTION .BR libred_solar_elevation () calculates the Sun's elevation, and stores it, measured in degrees, in |