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 os.path
16import its.caps
17import its.device
18import its.image
19import its.objects
20import matplotlib
21from matplotlib import pylab
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) and
43                             not its.caps.mono_camera(props))
44        debug = its.caps.debug_mode()
45
46        # Expose for the scene with min sensitivity
47        sens_min, _ = props["android.sensor.info.sensitivityRange"]
48        # Digital gains might not be visible on RAW data
49        sens_max = props["android.sensor.maxAnalogSensitivity"]
50        sens_step = (sens_max - sens_min) / NUM_STEPS
51        s_ae, e_ae, _, _, f_dist = cam.do_3a(get_results=True)
52        s_e_prod = s_ae * e_ae
53
54        reqs = []
55        settings = []
56        for s in range(sens_min, sens_max, sens_step):
57            e = int(s_e_prod / float(s))
58            req = its.objects.manual_capture_request(s, e, f_dist)
59            reqs.append(req)
60            settings.append((s, e))
61
62        if debug:
63            caps = cam.do_capture(reqs, cam.CAP_RAW)
64        else:
65            # Get the active array width and height.
66            aax = props["android.sensor.info.preCorrectionActiveArraySize"]["left"]
67            aay = props["android.sensor.info.preCorrectionActiveArraySize"]["top"]
68            aaw = props["android.sensor.info.preCorrectionActiveArraySize"]["right"]-aax
69            aah = props["android.sensor.info.preCorrectionActiveArraySize"]["bottom"]-aay
70            # Compute stats on a grid across each image.
71            caps = cam.do_capture(reqs,
72                                  {"format": "rawStats",
73                                   "gridWidth": aaw/IMG_STATS_GRID,
74                                   "gridHeight": aah/IMG_STATS_GRID})
75
76        variances = []
77        for i, cap in enumerate(caps):
78            (s, e) = settings[i]
79
80            # Each shot should be noisier than the previous shot (as the gain
81            # is increasing). Use the variance of the center stats grid cell.
82            if debug:
83                gr = its.image.convert_capture_to_planes(cap, props)[1]
84                tile = its.image.get_image_patch(gr, 0.445, 0.445, 0.11, 0.11)
85                var = its.image.compute_image_variances(tile)[0]
86                img = its.image.convert_capture_to_rgb_image(cap, props=props)
87                its.image.write_image(img,
88                                      "%s_s=%05d_var=%f.jpg" % (NAME, s, var))
89            else:
90                # find white level
91                white_level = float(props["android.sensor.info.whiteLevel"])
92                _, var_image = its.image.unpack_rawstats_capture(cap)
93                cfa_idxs = its.image.get_canonical_cfa_order(props)
94                var = var_image[IMG_STATS_GRID/2, IMG_STATS_GRID/2,
95                                cfa_idxs[GR_PLANE]]/white_level**2
96            variances.append(var)
97            print "s=%d, e=%d, var=%e" % (s, e, var)
98
99        x = range(len(variances))
100        pylab.plot(x, variances, "-ro")
101        pylab.xticks(x)
102        pylab.xlabel("Setting Combination")
103        pylab.ylabel("Image Center Patch Variance")
104        matplotlib.pyplot.savefig("%s_variances.png" % NAME)
105
106        # Test that each shot is noisier than the previous one.
107        x.pop()  # remove last element in x index
108        for i in x:
109            msg = 'variances [i]: %.5f, [i+1]: %.5f, THRESH: %.2f' % (
110                    variances[i], variances[i+1], VAR_THRESH)
111            assert variances[i] < variances[i+1] / VAR_THRESH, msg
112
113if __name__ == "__main__":
114    main()
115
116