add bin/isdarktty

1 files changed, 20 insertions, 0 deletions

diff --git a/bin/isdarktty b/bin/isdarktty
new file mode 100755
index 0000000..8d01b89
--- /dev/null
+++ b/bin/isdarktty
@@ -0,0 +1,20 @@
+#!/bin/sh
+
+# compute luminance of the current terminal
+
+oldstty=$(stty -g)
+stty raw -echo min 0 time 0
+printf "\e]11;?\e\\"
+sleep 0.01
+read -r answer
+stty "$oldstty"
+
+awk -v s="$answer" 'BEGIN {
+	hex="123456789abcdef"
+	split(s, a, "")
+	r = (16 * index(hex, a[10]) + index(hex, a[11])) / 255
+	g = (16 * index(hex, a[15]) + index(hex, a[16])) / 255
+	b = (16 * index(hex, a[20]) + index(hex, a[21])) / 255
+	# print 0.33 * r + 0.5 * g + 0.16 * b
+	exit (0.33 * r + 0.5 * g + 0.16 * b > 0.5)
+}'