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-rw-r--r--Makefile20
-rw-r--r--blackbody.c252
-rw-r--r--generate-table.c2
-rw-r--r--libred.73
-rw-r--r--libred.h81
-rw-r--r--libred.h.021
-rw-r--r--libred_get_colour.345
l---------libred_get_colour_xy.31
-rw-r--r--libred_get_temperature.389
l---------libred_get_temperature_xy.31
-rw-r--r--libred_solar_elevation.311
-rw-r--r--solar.c70
12 files changed, 510 insertions, 86 deletions
diff --git a/Makefile b/Makefile
index 44116a7..c7663fe 100644
--- a/Makefile
+++ b/Makefile
@@ -11,7 +11,7 @@ include mk/$(OS).mk
LIB_MAJOR = 1
-LIB_MINOR = 0
+LIB_MINOR = 1
LIB_VERSION = $(LIB_MAJOR).$(LIB_MINOR)
@@ -22,9 +22,15 @@ OBJ =\
LOBJ = $(OBJ:.o=.lo)
MAN0 = libred.h.0
-MAN3 = libred_get_colour.3 libred_solar_elevation.3
MAN7 = libred.7
+MAN3 =\
+ libred_get_colour.3\
+ libred_get_colour_xy.3\
+ libred_get_temperature.3\
+ libred_get_temperature_xy.3\
+ libred_solar_elevation.3
+
all: libred.a libred.$(LIBEXT)
solar.o: libred.h
@@ -32,7 +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 > $@
@@ -66,9 +74,9 @@ install: libred.a libred.$(LIBEXT)
ln -sf -- libred.$(LIBMINOREXT) "$(DESTDIR)$(PREFIX)/lib/libred.$(LIBMAJOREXT)"
ln -sf -- libred.$(LIBMAJOREXT) "$(DESTDIR)$(PREFIX)/lib/libred.$(LIBEXT)"
cp -- libred.h "$(DESTDIR)$(PREFIX)/include"
- cp -- $(MAN0) "$(DESTDIR)$(MANPREFIX)/man0"
- cp -- $(MAN3) "$(DESTDIR)$(MANPREFIX)/man3"
- cp -- $(MAN7) "$(DESTDIR)$(MANPREFIX)/man7"
+ cp -P -- $(MAN0) "$(DESTDIR)$(MANPREFIX)/man0"
+ cp -P -- $(MAN3) "$(DESTDIR)$(MANPREFIX)/man3"
+ cp -P -- $(MAN7) "$(DESTDIR)$(MANPREFIX)/man7"
uninstall:
-rm -f -- "$(DESTDIR)$(PREFIX)/lib/libred.a"
diff --git a/blackbody.c b/blackbody.c
index 6edc85a..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));
@@ -76,70 +88,124 @@ 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
+
+/**
+ * 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)
+{
+#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 xyY 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
+ * between the CIE xy values for two colour temperatures.
+ * The two colours should be the closest below the desired
+ * colour temperature, and the closest above the desired
+ * colour temperature
*
* @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 x Output parameter for the CIE x value
+ * @param y Output parameter for the CIE y value
*/
static void
-interpolate(double x1, double y1, double x2, double y2, double temp, double *r, double *g, double *b)
+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;
- double x = x1 * (1 - weight) + x2 * weight;
- double y = y1 * (1 - weight) + y2 * weight;
- ciexyy_to_srgb(x, y, 1.0, r, g, b);
+ *x = x1 * (1 - weight) + x2 * weight;
+ *y = y1 * (1 - weight) + y2 * weight;
}
-/**
- * Get the [0, 1] sRGB 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 r Output parameter for the “red” value
- * @param g Output parameter for the green value
- * @param b Output parameter for the blue value
- * @return 0 on succeess, -1 on error
- * @throws EDOM The selected temperature is below 1000K
- */
+
+int
+libred_get_colour_xy(long int temp, double *x, double *y)
+{
+ double x1, y1, x2, y2;
+ size_t i;
+ long int tmp;
+
+ if (temp > LIBRED_HIGHEST_TEMPERATURE)
+ temp = LIBRED_HIGHEST_TEMPERATURE;
+
+ if (temp < LIBRED_LOWEST_TEMPERATURE) {
+ errno = EDOM;
+ return -1;
+ }
+
+ tmp = temp - LIBRED_LOWEST_TEMPERATURE;
+
+ i = (size_t)(tmp / LIBRED_DELTA_TEMPERATURE);
+ if (tmp % LIBRED_DELTA_TEMPERATURE) {
+ x1 = xy_table[i].x;
+ y1 = xy_table[i].y;
+ x2 = xy_table[i + 1].x;
+ y2 = xy_table[i + 1].y;
+ interpolate(x1, y1, x2, y2, (double)temp, x, y);
+ } else {
+ *x = xy_table[i].x;
+ *y = xy_table[i].y;
+ }
+
+ return 0;
+}
+
+
int
libred_get_colour(long int temp, double *r, double *g, double *b)
{
@@ -156,14 +222,16 @@ libred_get_colour(long int temp, double *r, double *g, double *b)
}
tmp = temp - LIBRED_LOWEST_TEMPERATURE;
-
+
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(x1, y1, x2, y2, (double)temp, r, g, b);
+ interpolate(x1, y1, x2, y2, (double)temp, &x, &y);
+ ciexyy_to_srgb(x, y, 1, r, g, b);
} else {
*r = rgb_table[i].r;
*g = rgb_table[i].g;
@@ -172,6 +240,76 @@ libred_get_colour(long int temp, double *r, double *g, double *b)
return 0;
}
+
+
+double
+libred_get_temperature_xy(double x, double y, double *x_error, double *y_error)
+{
+ size_t i = 0, j;
+ double x1, y1, x2, y2, dx, dy, xd, yd, t, d2;
+ double best_temp = -1, best_d2 = INFINITY;
+
+ if (!x_error)
+ x_error = &dx;
+ if (!y_error)
+ y_error = &dy;
+
+ x1 = xy_table[0].x;
+ y1 = xy_table[0].y;
+
+ for (j = 1; j < sizeof(xy_table) / sizeof(*xy_table); j++) {
+ x2 = xy_table[j].x;
+ y2 = xy_table[j].y;
+ dx = x2 - x1;
+ dy = y2 - y1;
+
+ t = ((x - x1) * dx + (y - y1) * dy) / (dx * dx + dy * dy);
+ if (!isfinite(t))
+ continue;
+ t = t < 0 ? 0 : t;
+ t = t > 1 ? 1 : t;
+
+ xd = dx * t + x1 - x;
+ yd = dy * t + y1 - y;
+ d2 = xd * xd + yd * yd;
+
+ if (d2 < best_d2) {
+ *x_error = xd;
+ *y_error = yd;
+ best_d2 = d2;
+ t *= (double)(j - i);
+ best_temp = (double)i + t;
+ }
+
+ i = j;
+ }
+
+ return best_temp * LIBRED_DELTA_TEMPERATURE + LIBRED_LOWEST_TEMPERATURE;
+}
+
+
+double
+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, 1, &r, &g, &b);
+
+ if (y)
+ *y = luma;
+ if (r_error)
+ *r_error = r;
+ if (g_error)
+ *g_error = g;
+ if (b_error)
+ *b_error = b;
+
+ return ret;
+}
+
#endif
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"
diff --git a/libred.7 b/libred.7
index f7d3141..f81445b 100644
--- a/libred.7
+++ b/libred.7
@@ -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),
diff --git a/libred.h b/libred.h
index 3b0e489..9d59d39 100644
--- a/libred.h
+++ b/libred.h
@@ -3,6 +3,9 @@
#define LIBRED_H
+/* bug fix: */
+#define libred_solar_elevation libred_solar_elevation__int
+
/**
* Approximate apparent size of the Sun in degrees
@@ -143,7 +146,7 @@
* @return 0 on success, -1 on failure
* @throws Any error specified for clock_gettime(3) on error
*/
-double libred_solar_elevation(double, double, double *);
+int libred_solar_elevation(double, double, double *);
/**
@@ -212,6 +215,82 @@ 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 [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 *);
+
+/**
+ * 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
diff --git a/libred.h.0 b/libred.h.0
index 3dd97b8..606e234 100644
--- a/libred.h.0
+++ b/libred.h.0
@@ -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_xy (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 afd0a7f..d6649d2 100644
--- a/libred_get_colour.3
+++ b/libred_get_colour.3
@@ -1,20 +1,23 @@
.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>
int \fBlibred_get_colour\fP(long int \fItemp\fP, double *\fIr\fP, double *\fIg\fP, double *\fIb\fP);
+int \fBlibred_get_colour_xy\fP(long int \fItemp\fP, double *\fIx\fP, double *\fIy\fP);
.fi
.PP
Link with
-.IR -lred .
+.I -lred
+.IR -lm .
.SH DESCRIPTION
.BR libred_get_colour ()
gets or interpolates the colour temperature for
.I temp
-kelvins, and returns the colour temperature in sRGB. The values,
+kelvins, and returns the colour temperature in sRGB, with the
+sRGB transfer function applied. The values,
between 0.0 and 1.0, for the \(dqred\(dq, green, and blue channels
are stored in
.IR *r ,
@@ -49,14 +52,45 @@ ceiling
.TP
round to nearest
.I (temp - LIBRED_LOWEST_TEMPERATURE + LIBRED_DELTA_TEMPERATURE / 2) / LIBRED_DELTA_TEMPERATURE * LIBRED_DELTA_TEMPERATURE + LIBRED_LOWEST_TEMPERATURE
+.PP
+The
+.BR libred_get_colour_xy ()
+function is the same as the
+.BR libred_get_colour ()
+except it uses the CIE xy colour space instead of sRGB
+(of course without any transfer function). This means
+that the chroma values x and y are stored in
+.I *x
+and
+.IR *y ,
+and the CIE Y value shall be assumed to be 1 for
+equivalence with the
+.BR libred_get_colour ()
+function.
+.PP
+Neither
+.IR r ,
+.IR g ,
+.IR b ,
+.IR x ,
+nor
+.I y
+may be
+.IR NULL .
.SH RETURN VALUE
Upon successful completion, the
.BR libred_get_colour ()
+and
+.BR libred_get_colour_xy ()
function returns 0. On failure, the function returns -1 and sets
.I errno
to indicate the error.
.SH ERRORS
-The function may fail if:
+The
+.BR libred_get_colour ()
+and
+.BR libred_get_colour_xy ()
+functions may fail if:
.TP
.B EDOM
If
@@ -67,4 +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_colour_xy.3 b/libred_get_colour_xy.3
new file mode 120000
index 0000000..1d7ee17
--- /dev/null
+++ b/libred_get_colour_xy.3
@@ -0,0 +1 @@
+libred_get_colour.3 \ No newline at end of file
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 9bb4b0a..fa2df7e 100644
--- a/libred_solar_elevation.3
+++ b/libred_solar_elevation.3
@@ -5,11 +5,12 @@ libred_solar_elevation \- Calculate the Sun's apparent elevation
.nf
#include <libred.h>
-int \fBlibred_solar_elevation\fP(double \fIlatitude\fP, double \fIlongitude\fP, double *\felevation\fP);
+int \fBlibred_solar_elevation\fP(double \fIlatitude\fP, double \fIlongitude\fP, double *\fIelevation\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
@@ -27,11 +28,13 @@ Other values may or may not work, no error is thrown if used.
.SH RETURN VALUE
Upon successful completion, the
.BR libred_solar_elevation ()
-return 0, on failure it returns -1 and sets
+function returns 0, on failure it returns -1 and sets
.I errno
to indicate the error.
.SH ERRORS
-The function may fail for any reason specified for
+The
+.BR libred_solar_elevation ()
+function may fail for any reason specified for
.BR clock_gettime (3).
.SH SEE ALSO
.BR libred.h (0),
diff --git a/solar.c b/solar.c
index 3980014..697c960 100644
--- a/solar.c
+++ b/solar.c
@@ -1,5 +1,6 @@
/* See LICENSE file for copyright and license details. */
#include "libred.h"
+#undef libred_solar_elevation
#include <math.h>
#include <time.h>
#include <errno.h>
@@ -21,6 +22,50 @@
#endif
+/* old erroneous function declarations: */
+double libred_solar_elevation(double latitude, double longitude, double *elevation);
+
+
+#if !defined(_POSIX_TIMERS)
+# ifndef CLOCK_REALTIME_COARSE
+# define CLOCK_REALTIME_COARSE 0
+# endif
+# ifndef CLOCK_REALTIME
+# define CLOCK_REALTIME 0
+# endif
+# if defined(_WIN32)
+# include <windows.h>
+int
+clock_gettime(int clockid, struct timespec *ts)
+{
+ /* https://learn.microsoft.com/en-us/windows/win32/sysinfo/file-times */
+ FILETIME ft;
+ ULARGE_INTEGER u64;
+ (void) clockid;
+ GetSystemTimePreciseAsFileTime(&ft);
+ u64.LowPart = ft.dwLowDateTime;
+ u64.HighPart = ft.dwHighDateTime;
+ ts->tv_sec = (time_t)(uli.QuadPart / 100000000ULL - 11644473600ULL);
+ ts->tv_nsec = (long)(uli.QuadPart % 100000000ULL * 10ULL);
+ return 0;
+}
+# else
+# include <sys/time.h>
+int
+clock_gettime(int clockid, struct timespec *ts)
+{
+ struct timeval tv;
+ (void) clockid;
+ if (gettimeofday(&tv, NULL))
+ return -1;
+ ts->tv_sec = tv.tv_sec;
+ ts->tv_nsec = tv.tv_usec * 1000;
+ return 0;
+}
+# endif
+#endif
+
+
/**
* Get current Julian Centuries time (100 Julian Days since J2000)
* and Julian Day time
@@ -163,7 +208,7 @@ static double
sun_equation_of_centre(double t)
{
double a = sun_geometric_mean_anomaly(t), r;
- r = sin(1.0 * a) * fma(fma(-0.000014, t, 0.004817), t, 1.914602);
+ r = sin(1.0 * a) * fma(fma(-0.000014, t, -0.004817), t, 1.914602);
r = fma(sin(2.0 * a), fma(-0.000101, t, 0.019993), r);
r = fma(sin(3.0 * a), 0.000289, r);
return radians(r);
@@ -241,7 +286,7 @@ solar_declination(double t)
* between apparent and mean solar time
*
* @param t The time in Julian Centuries
- * @return The equation of time, in degrees
+ * @return The equation of time, in minutes of time
*/
static double
equation_of_time(double t)
@@ -249,13 +294,14 @@ equation_of_time(double t)
double l = sun_geometric_mean_longitude(t);
double e = earth_orbit_eccentricity(t);
double m = sun_geometric_mean_anomaly(t);
- double y = pow(tan(corrected_mean_ecliptic_obliquity(t) / 2.0), 2.0);
+ double y = tan(corrected_mean_ecliptic_obliquity(t) / 2.0);
double r, c, s;
+ y *= y;
s = y * sin(2.0 * l);
c = y * cos(2.0 * l);
r = fma(fma(4.0, c, -2.0), e * sin(m), s);
- r = fma(pow(0.50 * y, 2.0), sin(-4.0 * l), r);
- r = fma(pow(1.25 * e, 2.0), sin(-2.0 * m), r);
+ r = fma(-0.5 * y*y, sin(4.0 * l), r);
+ r = fma(-1.25 * e*e, sin(2.0 * m), r);
return 4.0 * degrees(r);
}
@@ -296,8 +342,8 @@ solar_elevation_from_time(double tc, double td, double latitude, double longitud
* @return 0 on success, -1 on failure
* @throws Any error specified for clock_gettime(3) on error
*/
-double
-libred_solar_elevation(double latitude, double longitude, double *elevation)
+int
+libred_solar_elevation__int(double latitude, double longitude, double *elevation)
{
double tc, td;
if (julian_time(&tc, &td))
@@ -307,6 +353,16 @@ libred_solar_elevation(double latitude, double longitude, double *elevation)
}
/**
+ * Kept for binary compatibility
+ */
+double
+libred_solar_elevation(double latitude, double longitude, double *elevation)
+{
+ int r = libred_solar_elevation__int(latitude, longitude, elevation);
+ return (double)r;
+}
+
+/**
* This function is obsolete
*/
int