sct

Commit: 2513bfa7e36e0fc2dcb4988b330d10d69fe168dc
Author: Fabian Foerg
Date:   Fri, 20 Nov 2015 19:32:42 -0500

Initial commit

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README.md
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sct.c
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diff --git a/README.md b/README.md
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+# About
+
+Sct (set color temperature) is a UNIX tool which allows you to set the color
+temperature of your screen. It is simpler than Redshift and f.lux.
+
+Original code was published by Ted Unangst:
+http://www.tedunangst.com/flak/post/sct-set-color-temperature
+
+Minor modifications were made in order to get sct to:
+- compile on Ubuntu 14.04
+- iterate over all screens of the default display and change the color
+  temperature
+- free the Display structure
+- return 0
+
+# Installation
+
+Compile the code using the following command:
+
+~~~
+cc -std=c99 -O2 -I /usr/X11R6/include -o sct sct.c -L /usr/X11R6/lib -lm -lX11 -lXrandr
+~~~
+
+Execute sct using the following command:
+
+~~~
+./sct 3700
+~~~
+
+The first parameter (`3700` above) denotes the color temperature and can be
+between `1000` and `10000`.
+If `sct` is called without parameters, sct sets the color temperature to `6500`.
+
diff --git a/sct.c b/sct.c
@@ -0,0 +1,111 @@
+/*
+ * sct - set color temperature
+ *
+ * Compile the code using the following command:
+ * cc -std=c99 -O2 -I /usr/X11R6/include -o sct sct.c -L /usr/X11R6/lib -lm -lX11 -lXrandr
+ *
+ * Original code published by Ted Unangst:
+ * http://www.tedunangst.com/flak/post/sct-set-color-temperature
+ *
+ * Modified by Fabian Foerg in order to:
+ * - compile on Ubuntu 14.04
+ * - iterate over all screens of the default display and change the color
+ *   temperature
+ * - free the Display structure
+ * - return 0
+ */
+
+#include <inttypes.h>
+#include <math.h>
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+
+#include <X11/Xatom.h>
+#include <X11/Xlib.h>
+#include <X11/Xlibint.h>
+#include <X11/Xproto.h>
+#include <X11/extensions/Xrandr.h>
+#include <X11/extensions/Xrender.h>
+
+/* cribbed from redshift, but truncated with 500K steps */
+static const struct { float r; float g; float b; } whitepoints[] = {
+	{ 1.00000000,  0.18172716,  0.00000000, }, /* 1000K */
+	{ 1.00000000,  0.42322816,  0.00000000, },
+	{ 1.00000000,  0.54360078,  0.08679949, },
+	{ 1.00000000,  0.64373109,  0.28819679, },
+	{ 1.00000000,  0.71976951,  0.42860152, },
+	{ 1.00000000,  0.77987699,  0.54642268, },
+	{ 1.00000000,  0.82854786,  0.64816570, },
+	{ 1.00000000,  0.86860704,  0.73688797, },
+	{ 1.00000000,  0.90198230,  0.81465502, },
+	{ 1.00000000,  0.93853986,  0.88130458, },
+	{ 1.00000000,  0.97107439,  0.94305985, },
+	{ 1.00000000,  1.00000000,  1.00000000, }, /* 6500K */
+	{ 0.95160805,  0.96983355,  1.00000000, },
+	{ 0.91194747,  0.94470005,  1.00000000, },
+	{ 0.87906581,  0.92357340,  1.00000000, },
+	{ 0.85139976,  0.90559011,  1.00000000, },
+	{ 0.82782969,  0.89011714,  1.00000000, },
+	{ 0.80753191,  0.87667891,  1.00000000, },
+	{ 0.78988728,  0.86491137,  1.00000000, }, /* 10000K */
+	{ 0.77442176,  0.85453121,  1.00000000, },
+};
+
+static void
+sct_for_screen(Display *dpy, int screen, int temp)
+{
+	Window root = RootWindow(dpy, screen);
+	XRRScreenResources *res = XRRGetScreenResourcesCurrent(dpy, root);
+
+	temp -= 1000;
+	double ratio = temp % 500 / 500.0;
+#define AVG(c) whitepoints[temp / 500].c * (1 - ratio) + whitepoints[temp / 500 + 1].c * ratio
+	double gammar = AVG(r);
+	double gammag = AVG(g);
+	double gammab = AVG(b);
+
+	int num_crtcs = res->ncrtc;
+	for (int c = 0; c < res->ncrtc; c++) {
+		int crtcxid = res->crtcs[c];
+		XRRCrtcInfo *crtc_info = XRRGetCrtcInfo(dpy, res, crtcxid);
+
+		int size = XRRGetCrtcGammaSize(dpy, crtcxid);
+
+		XRRCrtcGamma *crtc_gamma = XRRAllocGamma(size);
+
+		for (int i = 0; i < size; i++) {
+			double g = 65535.0 * i / size;
+			crtc_gamma->red[i] = g * gammar;
+			crtc_gamma->green[i] = g * gammag;
+			crtc_gamma->blue[i] = g * gammab;
+		}
+		XRRSetCrtcGamma(dpy, crtcxid, crtc_gamma);
+
+		XFree(crtc_gamma);
+	}
+}
+
+int
+main(int argc, char **argv)
+{
+	Display *dpy = XOpenDisplay(NULL);
+	int screens = XScreenCount(dpy);
+
+	int temp = 6500;
+	if (argc > 1)
+		temp = atoi(argv[1]);
+	if (temp < 1000 || temp > 10000)
+		temp = 6500;
+
+	for (int screen = 0; screen < screens; screen++)
+		sct_for_screen(dpy, screen, temp);
+
+	XCloseDisplay(dpy);
+
+	return 0;
+}
+