OpenDroneMap-ODM/opendm/gsd.py

140 wiersze
5.2 KiB
Python

import os
import json
import numpy as np
from repoze.lru import lru_cache
from opendm import log
def rounded_gsd(reconstruction_json, default_value=None, ndigits=0, ignore_gsd=False):
"""
:param reconstruction_json path to OpenSfM's reconstruction.json
:return GSD value rounded. If GSD cannot be computed, or ignore_gsd is set, it returns a default value.
"""
if ignore_gsd:
return default_value
gsd = opensfm_reconstruction_average_gsd(reconstruction_json)
if gsd is not None:
return round(gsd, ndigits)
else:
return default_value
def image_scale_factor(target_resolution, reconstruction_json, gsd_error_estimate = 0.1):
"""
:param target_resolution resolution the user wants have in cm / pixel
:param reconstruction_json path to OpenSfM's reconstruction.json
:param gsd_error_estimate percentage of estimated error in the GSD calculation to set an upper bound on resolution.
:return A down-scale (<= 1) value to apply to images to achieve the target resolution by comparing the current GSD of the reconstruction.
If a GSD cannot be computed, it just returns 1. Returned scale values are never higher than 1.
"""
gsd = opensfm_reconstruction_average_gsd(reconstruction_json)
if gsd is not None and target_resolution > 0:
gsd = gsd * (1 + gsd_error_estimate)
return min(1, gsd / target_resolution)
else:
return 1
def cap_resolution(resolution, reconstruction_json, gsd_error_estimate = 0.1, ignore_gsd=False):
"""
:param resolution resolution in cm / pixel
:param reconstruction_json path to OpenSfM's reconstruction.json
:param gsd_error_estimate percentage of estimated error in the GSD calculation to set an upper bound on resolution.
:param ignore_gsd when set to True, forces the function to just return resolution.
:return The max value between resolution and the GSD computed from the reconstruction.
If a GSD cannot be computed, or ignore_gsd is set to True, it just returns resolution. Units are in cm / pixel.
"""
if ignore_gsd:
return resolution
gsd = opensfm_reconstruction_average_gsd(reconstruction_json)
if gsd is not None:
gsd = gsd * (1 - gsd_error_estimate)
if gsd > resolution:
log.ODM_WARNING('Maximum resolution set to GSD - {}% ({} cm / pixel, requested resolution was {} cm / pixel)'.format(gsd_error_estimate * 100, round(gsd, 2), round(resolution, 2)))
return gsd
else:
return resolution
else:
log.ODM_WARNING('Cannot calculate GSD, using requested resolution of {}'.format(round(resolution, 2)))
return resolution
@lru_cache(maxsize=None)
def opensfm_reconstruction_average_gsd(reconstruction_json):
"""
Computes the average Ground Sampling Distance of an OpenSfM reconstruction.
:param reconstruction_json path to OpenSfM's reconstruction.json
:return Ground Sampling Distance value (cm / pixel) or None if
a GSD estimate cannot be compute
"""
if not os.path.isfile(reconstruction_json):
raise IOError(reconstruction_json + " does not exist.")
with open(reconstruction_json) as f:
data = json.load(f)
# Calculate median height from sparse reconstruction
reconstruction = data[0]
point_heights = []
for pointId in reconstruction['points']:
point = reconstruction['points'][pointId]
point_heights.append(point['coordinates'][2])
ground_height = np.median(point_heights)
gsds = []
for shotImage in reconstruction['shots']:
shot = reconstruction['shots'][shotImage]
if shot['gps_dop'] < 999999:
camera = reconstruction['cameras'][shot['camera']]
shot_height = shot['translation'][2]
focal_ratio = camera['focal']
gsds.append(calculate_gsd_from_focal_ratio(focal_ratio,
shot_height - ground_height,
camera['width']))
if len(gsds) > 0:
mean = np.mean(gsds)
if mean > 0:
return mean
return None
def calculate_gsd(sensor_width, flight_height, focal_length, image_width):
"""
:param sensor_width in millimeters
:param flight_height in meters
:param focal_length in millimeters
:param image_width in pixels
:return Ground Sampling Distance
>>> round(calculate_gsd(13.2, 100, 8.8, 5472), 2)
2.74
>>> calculate_gsd(13.2, 100, 0, 2000)
>>> calculate_gsd(13.2, 100, 8.8, 0)
"""
if sensor_width != 0:
return calculate_gsd_from_focal_ratio(focal_length / sensor_width,
flight_height,
image_width)
else:
return None
def calculate_gsd_from_focal_ratio(focal_ratio, flight_height, image_width):
"""
:param focal_ratio focal length (mm) / sensor_width (mm)
:param flight_height in meters
:param image_width in pixels
:return Ground Sampling Distance
"""
if focal_ratio == 0 or image_width == 0:
return None
return ((flight_height * 100) / image_width) / focal_ratio