def synthesize(exp, luck, focal):
logger.debug('synthesizing. target EV: {}'.format(exp))
# TODO: use bounds during synthesis so we can't generate invalid values.
random.seed()
evFocal = exposure.seconds_to_ev('1/' + focal + 's')
evShutter = evFocal + random.uniform(
-LUCK_SCALE_FACTOR*luck, LUCK_SCALE_FACTOR*luck)
evTarget = exp + random.uniform(
-LUCK_SCALE_FACTOR*luck, LUCK_SCALE_FACTOR*luck)
# evTarget = evShutter + evAperture + evIso
# evTarget - evShutter = evAperture + evIso
remainder = evTarget - evShutter
isoLower = max(MIN_ISO, remainder - MAX_APERTURE)
isoUpper = min(MAX_ISO, remainder - MIN_APERTURE)
evIso = random.uniform(isoLower, isoUpper)
evAperture = evTarget - evIso - evShutter
logger.debug('values synthesized: {}'.format(
exposure.evs_to_exposure(evShutter, evAperture, evIso)))
return evShutter, evAperture, evIso
isoLower = max(MIN_ISO, remainder - MAX_APERTURE)
isoUpper = min(MAX_ISO, remainder - MIN_APERTURE)
evIso = random.uniform(isoLower, isoUpper)
evAperture = evTarget - evIso - evShutter
logger.debug('values synthesized: {}'.format(
exposure.evs_to_exposure(evShutter, evAperture, evIso)))
return evShutter, evAperture, evIso
if __name__ == "__main__":
logging.basicConfig(level=logging.DEBUG)
usage = "usage: %prog [options]"
parser = OptionParser()
parser.add_option(
'-e', '--exposure',
action='store', type='int', dest='exp', default=exposure.SUNNY,
help='Exposure value in EV (Sunny 16: ~{0:.0f} EV)'.format(
exposure.SUNNY))
parser.add_option(
'-l', '--luck',
action='store', type='float', dest='luck', default=1,
help='How lucky are you feeling? (variability)')
parser.add_option(
'-f', '--focal',
action='store', type='string', dest='focal', default='50',
help='Lens focal length (for handheld limit)')
(options, args) = parser.parse_args()
evShutter, evAperture, evIso = synthesize(
options.exp, options.luck, options.focal)
print exposure.evs_to_exposure(evShutter, evAperture, evIso)