webcam-brightness.py

#!/usr/bin/env python3
from io import BytesIO
from subprocess import check_output
import sys

from PIL import Image, ImageDraw

MAX_VALUE = 255
MIN_VALUE = 0
DESIRED_BRIGHTNESS = 128
BRIGHTNESS_ALLOWANCE = 6
STEP = 1
MIN_GAIN = 6
TEXT_SHADOW_OFFSET = 1
TEXT_SHADOW_X = 4
TEXT_SHADOW_Y_OFFSET = 13

class WebcamBrightness(object):
    def __init__(self, image):
        box = int(image.size[0] / 3), int(image.size[1] / 3), int(image.size[0] * (2 / 3)), int(image.size[1] * (2 / 3))
        self.image = image.convert("L").crop(box)

    def get_brightness(self):
        s = 0
        for x in range(self.image.size[0]):
            for y in range(self.image.size[1]):
                s += self.image.getpixel((x, y))
        return s / (self.image.size[0] * self.image.size[1])

    @staticmethod
    def get_webcam_bytes():
        return check_output(["fswebcam", "-q", "--jpeg", "100", "--banner-colour",
                             "#FF000000", "--line-colour", "#FF000000", "/dev/stdout"])

    @staticmethod
    def get_webcam_screenshot():
        b = BytesIO(WebcamBrightness.get_webcam_bytes())
        return Image.open(b)

    @staticmethod
    def get_webcam_config():
        return int(check_output(["v4l2-ctl", "-C", "exposure"]).decode().split(": ")[1]), \
               int(check_output(["v4l2-ctl", "-C", "gain"]).decode().split(": ")[1])

    @staticmethod
    def set_webcam_config(exposure, gain):
        check_output(["v4l2-ctl", "-c", "exposure={0},gain={1}".format(exposure, gain)])

    @staticmethod
    def tune_webcam(image):
        wb = WebcamBrightness(image)
        brightness = wb.get_brightness()
        exposure, gain = WebcamBrightness.get_webcam_config()
        if brightness < DESIRED_BRIGHTNESS - BRIGHTNESS_ALLOWANCE:
            if exposure == MAX_VALUE:
                WebcamBrightness.set_webcam_config(exposure, gain + STEP)
            else:
                WebcamBrightness.set_webcam_config(exposure + STEP, gain)
        elif brightness > DESIRED_BRIGHTNESS + BRIGHTNESS_ALLOWANCE:
            if gain - STEP >= MIN_GAIN:
                WebcamBrightness.set_webcam_config(exposure, gain - STEP)
            elif exposure != MIN_VALUE:
                WebcamBrightness.set_webcam_config(exposure - STEP, gain)
        return brightness, exposure, gain


if __name__ == "__main__":
    image = WebcamBrightness.get_webcam_screenshot()
    info = WebcamBrightness.tune_webcam(image)
    draw = ImageDraw.Draw(image)
    draw.text((TEXT_SHADOW_X + TEXT_SHADOW_OFFSET, image.size[1] - TEXT_SHADOW_Y_OFFSET + TEXT_SHADOW_OFFSET),
              "B: {0:.2f}, E: {1}, G: {2}".format(info[0], info[1], info[2]), fill=(0, 0, 0))
    draw.text((TEXT_SHADOW_X, image.size[1] - TEXT_SHADOW_Y_OFFSET),
              "B: {0:.2f}, E: {1}, G: {2}".format(info[0], info[1], info[2]), fill=(255, 255, 255))
    buffer = BytesIO()
    image.save(buffer, "JPEG", quality=97)
    buffer.seek(0)
    sys.stdout.buffer.write(buffer.read())