camera_calibration.py

import picamera
import picamera.array
import numpy as np
import cv2
delta_gain = 0.1

with picamera.PiCamera() as camera:
    camera.resolution = (1280, 720)
    camera.awb_mode = 'off'
    # Start off with ridiculously low gains
    rg, bg = (0.5, 0.5)
    camera.awb_gains = (rg, bg)
    with picamera.array.PiRGBArray(camera, size=(128, 72)) as output:
        # Allow 30 attempts to fix AWB
        for i in range(30):
            # Capture a tiny resized image in RGB format, and extract the
            # average R, G, and B values
            camera.capture(output, format='rgb', resize=(128, 72), use_video_port=True)
            r, g, b = (np.mean(output.array[..., i]) for i in range(3))
            cv2.imshow("image", output.array)
            key = cv2.waitKey(1) & 0xFF
            print('R:%5.2f, B:%5.2f = (%5.2f, %5.2f, %5.2f)' % (
                rg, bg, r, g, b))
            # Adjust R and B relative to G, but only if they're significantly
            # different (delta +/- 2)
            if abs(r - g) > 2:
                if r > g:
                    rg -= delta_gain
                else:
                    rg += delta_gain
            if abs(b - g) > 1:
                if b > g:
                    bg -= delta_gain
                else:
                    bg += delta_gain
            camera.awb_gains = (rg, bg)
            output.seek(0)
            output.truncate()