Capture luminance still Raspberry PI camera

capture-luminance.py

# python3
# based on https://raspberrypi.stackexchange.com/questions/58871/pi-camera-v2-fast-full-sensor-capture-mode-with-downsampling/58941#58941
import time
import picamera
import numpy as np
from PIL import Image

RESOLUTION = (1640, 1232)

# Calculate the actual image size in the stream (accounting for rounding
# of the resolution)
# Capturing yuv will round horizontal resolution to 16 multiple and vertical to 32 multiple
# see: https://picamera.readthedocs.io/en/release-1.12/recipes2.html#unencoded-image-capture-yuv-format
fwidth = (RESOLUTION[0] + 31) // 32 * 32
fheight = (RESOLUTION[1] + 15) // 16 * 16
print(f'frame size {fwidth}x{fheight}')

with picamera.PiCamera(
        sensor_mode=4,  # 1640x1232, full FoV, binning 2x2
        resolution=RESOLUTION,
        framerate=40
) as camera:
    print('camera setup')
    camera.rotation = 180
    time.sleep(2)  # let the camera warm up and set gain/white balance

    print('starting capture')
    y_data = np.empty((fheight, fwidth), dtype=np.uint8)
    try:
        camera.capture(y_data, 'yuv')  # YUV420
    except IOError:
        pass
    y_data = y_data[:RESOLUTION[1], :RESOLUTION[0]]  # crop numpy array to RESOLUTION
    # y_data now contains the Y-plane only

    print('convert to Pillow image')
    im = Image.fromarray(y_data, mode='L')  # using luminance mode

    print('saving...')
    im.save('test.jpg')
    im.save('test.bmp')

print('done')