1# Copyright 2014 The Android Open Source Project
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7#      http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12# See the License for the specific language governing permissions and
13# limitations under the License.
14
15import its.device
16import its.caps
17import its.objects
18import its.image
19import os.path
20from matplotlib import pylab
21import matplotlib
22
23GR_PLANE = 1  # GR plane index in RGGB data
24IMG_STATS_GRID = 9  # find used to find the center 11.11%
25NAME = os.path.basename(__file__).split(".")[0]
26NUM_STEPS = 5
27VAR_THRESH = 1.01  # each shot must be 1% noisier than previous
28
29
30def main():
31    """Capture a set of raw images with increasing gains and measure the noise.
32
33    Capture raw-only, in a burst.
34    """
35
36    with its.device.ItsSession() as cam:
37
38        props = cam.get_camera_properties()
39        its.caps.skip_unless(its.caps.raw16(props) and
40                             its.caps.manual_sensor(props) and
41                             its.caps.read_3a(props) and
42                             its.caps.per_frame_control(props))
43        debug = its.caps.debug_mode()
44
45        # Expose for the scene with min sensitivity
46        sens_min, _ = props["android.sensor.info.sensitivityRange"]
47        # Digital gains might not be visible on RAW data
48        sens_max = props["android.sensor.maxAnalogSensitivity"]
49        sens_step = (sens_max - sens_min) / NUM_STEPS
50        s_ae, e_ae, _, _, f_dist = cam.do_3a(get_results=True)
51        s_e_prod = s_ae * e_ae
52
53        reqs = []
54        settings = []
55        for s in range(sens_min, sens_max, sens_step):
56            e = int(s_e_prod / float(s))
57            req = its.objects.manual_capture_request(s, e, f_dist)
58            reqs.append(req)
59            settings.append((s, e))
60
61        if debug:
62            caps = cam.do_capture(reqs, cam.CAP_RAW)
63        else:
64            # Get the active array width and height.
65            aax = props["android.sensor.info.activeArraySize"]["left"]
66            aay = props["android.sensor.info.activeArraySize"]["top"]
67            aaw = props["android.sensor.info.activeArraySize"]["right"]-aax
68            aah = props["android.sensor.info.activeArraySize"]["bottom"]-aay
69            # Compute stats on a grid across each image.
70            caps = cam.do_capture(reqs,
71                                  {"format": "rawStats",
72                                   "gridWidth": aaw/IMG_STATS_GRID,
73                                   "gridHeight": aah/IMG_STATS_GRID})
74
75        variances = []
76        for i, cap in enumerate(caps):
77            (s, e) = settings[i]
78
79            # Each shot should be noisier than the previous shot (as the gain
80            # is increasing). Use the variance of the center stats grid cell.
81            if debug:
82                gr = its.image.convert_capture_to_planes(cap, props)[1]
83                tile = its.image.get_image_patch(gr, 0.445, 0.445, 0.11, 0.11)
84                var = its.image.compute_image_variances(tile)[0]
85                img = its.image.convert_capture_to_rgb_image(cap, props=props)
86                its.image.write_image(img,
87                                      "%s_s=%05d_var=%f.jpg" % (NAME, s, var))
88            else:
89                # find white level
90                white_level = float(props["android.sensor.info.whiteLevel"])
91                _, var_image = its.image.unpack_rawstats_capture(cap)
92                cfa_idxs = its.image.get_canonical_cfa_order(props)
93                var = var_image[IMG_STATS_GRID/2, IMG_STATS_GRID/2,
94                                cfa_idxs[GR_PLANE]]/white_level**2
95            variances.append(var)
96            print "s=%d, e=%d, var=%e" % (s, e, var)
97
98        x = range(len(variances))
99        pylab.plot(x, variances, "-ro")
100        pylab.xticks(x)
101        pylab.xlabel("Setting Combination")
102        pylab.ylabel("Image Center Patch Variance")
103        matplotlib.pyplot.savefig("%s_variances.png" % NAME)
104
105        # Test that each shot is noisier than the previous one.
106        x.pop()  # remove last element in x index
107        for i in x:
108            assert variances[i] < variances[i+1] / VAR_THRESH
109
110if __name__ == "__main__":
111    main()
112
113