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.pyplot
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
34    with its.device.ItsSession() as cam:
35
36        props = cam.get_camera_properties()
37        props = cam.override_with_hidden_physical_camera_props(props)
38        its.caps.skip_unless(its.caps.raw16(props) and
39                             its.caps.manual_sensor(props) and
40                             its.caps.read_3a(props) and
41                             its.caps.per_frame_control(props) and
42                             not its.caps.mono_camera(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        variances = []
54        for s in range(sens_min, sens_max, sens_step):
55
56            e = int(s_e_prod / float(s))
57            req = its.objects.manual_capture_request(s, e, f_dist)
58
59            # Capture raw in debug mode, rawStats otherwise
60            # Measure the variance. Each shot should be noisier than the
61            # previous shot (as the gain is increasing).
62            if debug:
63                cap = cam.do_capture(req, cam.CAP_RAW)
64                gr = its.image.convert_capture_to_planes(cap, props)[1]
65                tile = its.image.get_image_patch(gr, 0.445, 0.445, 0.11, 0.11)
66                var = its.image.compute_image_variances(tile)[0]
67                img = its.image.convert_capture_to_rgb_image(cap, props=props)
68                its.image.write_image(img, "%s_s=%05d_var=%f.jpg" %
69                                      (NAME, s, var))
70            else:
71                # Get the active array width and height.
72                aax = props["android.sensor.info.preCorrectionActiveArraySize"]["left"]
73                aay = props["android.sensor.info.preCorrectionActiveArraySize"]["top"]
74                aaw = props["android.sensor.info.preCorrectionActiveArraySize"]["right"]-aax
75                aah = props["android.sensor.info.preCorrectionActiveArraySize"]["bottom"]-aay
76                white_level = float(props["android.sensor.info.whiteLevel"])
77                cap = cam.do_capture(req,
78                                     {"format": "rawStats",
79                                      "gridWidth": aaw/IMG_STATS_GRID,
80                                      "gridHeight": aah/IMG_STATS_GRID})
81                _, var_image = its.image.unpack_rawstats_capture(cap)
82                cfa_idxs = its.image.get_canonical_cfa_order(props)
83                var = var_image[IMG_STATS_GRID/2, IMG_STATS_GRID/2,
84                                cfa_idxs[GR_PLANE]]/white_level**2
85
86            variances.append(var)
87            print "s=%d, e=%d, var=%e" % (s, e, var)
88
89        x = range(len(variances))
90        pylab.plot(x, variances, "-ro")
91        pylab.xticks(x)
92        pylab.xlabel("Setting Combination")
93        pylab.ylabel("Image Center Patch Variance")
94        matplotlib.pyplot.savefig("%s_variances.png" % NAME)
95
96        # Test that each shot is noisier than the previous one.
97        for i in range(len(variances) - 1):
98            msg = 'variances [i]: %.5f, [i+1]: %.5f, THRESH: %.2f' % (
99                    variances[i], variances[i+1], VAR_THRESH)
100            assert variances[i] < variances[i+1] / VAR_THRESH, msg
101
102if __name__ == "__main__":
103    main()
104