completed c implementation

ambientd.py

@@ -0,0 +1,73 @@
+#!/usr/bin/python
+
+# Simple daemon to change brightness based on luminance
+# TODO: add a config
+# TODO: add debug option
+# TODO: add dry-run
+# TODO automatically find the right brightness path and do not assume intel_backlight
+
+import time
+
+# Open the luminance sensor device file
+try:
+    luminance_file = open('/sys/bus/iio/devices/iio:device0/in_illuminance_raw', 'r')
+except OSError as err:
+    print(err)
+    exit(1)
+
+# max luminance of the screen - 100 (maybe)
+max_luminance = 400
+
+# get luminance value, on fail return the max
+def get_luminance():
+    try:
+        l = int(luminance_file.read())
+        luminance_file.seek(0)
+    except:
+        l = max_luminance
+    return l
+
+# Get the max brightness 
+max_brightness = 100
+with open('/sys/class/backlight/intel_backlight/max_brightness', 'r') as f:
+    max_brightness = int(f.read())
+min_brightness = int(max_brightness * 0.05)
+
+# loop delay in seconds
+delay = 3
+
+lum = [get_luminance()]*4
+user_offset = 0
+brightness_target = min_brightness
+brightness_old = min_brightness
+while True:
+    lum.append(lum.pop(0))
+    lum[0] = get_luminance()
+    
+    luminance = sum(lum)/len(lum)
+    luminance_percent = min(luminance/max_luminance, 1.0)
+    brightness_old = brightness_target
+    brightness_target = max(int(luminance_percent * max_brightness), min_brightness)
+    brightness_delta = abs((brightness_target - brightness_old)/brightness_old)
+
+    # if the brightness changes by more than 10% reduce the user offset, scaling
+    # with the delta, this accounts for large changes in brightness no longer
+    # corresponding to the adjustments that the user made to the brightness
+    if brightness_delta > 0.1:
+        user_offset = int(user_offset * max(min(1-(brightness_delta*1.2), 1), 0))
+
+    brightness_adjusted = min(max(brightness_target + user_offset, min_brightness), max_brightness)
+    b = open('/sys/class/backlight/intel_backlight/brightness', 'w')
+    b.write(str(brightness_adjusted))
+    b.close()
+
+    time.sleep(delay)
+
+    # if the value of the brightness changed then update the user offset
+    a = open('/sys/class/backlight/intel_backlight/actual_brightness')
+    x = int(a.read()) - brightness_target
+    a.close()
+    if brightness_target != max_brightness or x < 0:
+        user_offset = x
+
+    print("brightness target: ", brightness_target, "user offset: ", user_offset, "brightness adjusted: ", brightness_adjusted)