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# SPDX-License-Identifier: BSD-2-Clause
#
# Copyright (C) 2019, Raspberry Pi Ltd
#
# ctt_lux.py - camera tuning tool for lux level
from ctt_tools import *
"""
Find lux values from metadata and calculate Y
"""
def lux(Cam, Img):
shutter_speed = Img.exposure
gain = Img.againQ8_norm
aperture = 1
Cam.log += '\nShutter speed = {}'.format(shutter_speed)
Cam.log += '\nGain = {}'.format(gain)
Cam.log += '\nAperture = {}'.format(aperture)
patches = [Img.patches[i] for i in Img.order]
channels = [Img.channels[i] for i in Img.order]
return lux_calc(Cam, Img, patches, channels), shutter_speed, gain
"""
perform lux calibration on bayer channels
"""
def lux_calc(Cam, Img, patches, channels):
"""
find means color channels on grey patches
"""
ap_r = np.mean(patches[0][3::4])
ap_g = (np.mean(patches[1][3::4])+np.mean(patches[2][3::4]))/2
ap_b = np.mean(patches[3][3::4])
Cam.log += '\nAverage channel values on grey patches:'
Cam.log += '\nRed = {:.0f} Green = {:.0f} Blue = {:.0f}'.format(ap_r, ap_b, ap_g)
# print(ap_r, ap_g, ap_b)
"""
calculate channel gains
"""
gr = ap_g/ap_r
gb = ap_g/ap_b
Cam.log += '\nChannel gains: Red = {:.3f} Blue = {:.3f}'.format(gr, gb)
"""
find means color channels on image and scale by gain
note greens are averaged together (treated as one channel)
"""
a_r = np.mean(channels[0])*gr
a_g = (np.mean(channels[1])+np.mean(channels[2]))/2
a_b = np.mean(channels[3])*gb
Cam.log += '\nAverage channel values over entire image scaled by channel gains:'
Cam.log += '\nRed = {:.0f} Green = {:.0f} Blue = {:.0f}'.format(a_r, a_b, a_g)
# print(a_r, a_g, a_b)
"""
Calculate y with top row of yuv matrix
"""
y = 0.299*a_r + 0.587*a_g + 0.114*a_b
Cam.log += '\nY value calculated: {}'.format(int(y))
# print(y)
return int(y)
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