aboutsummaryrefslogtreecommitdiffstats
path: root/blackbody.c
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--blackbody.c42
1 files changed, 35 insertions, 7 deletions
diff --git a/blackbody.c b/blackbody.c
index 9dfe1a8..e654c9d 100644
--- a/blackbody.c
+++ b/blackbody.c
@@ -11,14 +11,17 @@
#include <stddef.h>
-struct xy {double x, y;};
-struct rgb {double r, g, b;};
-
-static struct xy xy_table[] = {
+/**
+ * Colour temperatures in CIE xy (xyY without Y)
+ */
+static struct xy {double x, y;} xy_table[] = {
#include "10deg-xy.i"
};
-static struct rgb rgb_table[] = {
+/**
+ * Colour temperatures in sRGB
+ */
+static struct rgb {double r, g, b;} rgb_table[] = {
#include "10deg-rgb.i"
};
@@ -105,12 +108,37 @@ interpolate(double x1, double y1, double x2, double y2, double temp, double *r,
/**
* 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 1000 K
+ * @throws EDOM The selected temperature is below 1000K
*/
int
libred_get_colour(long int temp, double *r, double *g, double *b)
@@ -126,7 +154,7 @@ libred_get_colour(long int temp, double *r, double *g, double *b)
return -1;
}
- if (temp % LIBRED_DELTA_TEMPERATURE) { /* TODO make optional */
+ if (temp % LIBRED_DELTA_TEMPERATURE) {
i = (temp - LIBRED_LOWEST_TEMPERATURE) / LIBRED_DELTA_TEMPERATURE;
x1 = xy_table[i].x;
y1 = xy_table[i].y;