启用自动曝光及其调节¶
通过 API 的 SetOptionValue() 函数，就可以设定当前打开设备的各类控制值。
启用自动曝光，就是设定 Option::EXPOSURE_MODE 为 0 。
以s1030为例，自动曝光时，可调节的设定有：
Option::MAX_GAIN最大增益。Option::MAX_EXPOSURE_TIME最大曝光时间。Option::DESIRED_BRIGHTNESS期望亮度。
以s2100/s210a为例，自动曝光可调节的设定有：
Option::MAX_GAIN最大增益。Option::MAX_EXPOSURE_TIME最大曝光时间。Option::DESIRED_BRIGHTNESS期望亮度。Option::MIN_EXPOSURE_TIME最小曝光时间。
参考代码片段：
s1030：
auto &&api = API::Create(argc, argv);
// auto-exposure: 0
api->SetOptionValue(Option::EXPOSURE_MODE, 0);
// max_gain: range [0,48], default 48
api->SetOptionValue(Option::MAX_GAIN, 48);
// max_exposure_time: range [0,240], default 240
api->SetOptionValue(Option::MAX_EXPOSURE_TIME, 240);
// desired_brightness: range [0,255], default 192
api->SetOptionValue(Option::DESIRED_BRIGHTNESS, 192);
LOG(INFO) << "Enable auto-exposure";
LOG(INFO) << "Set MAX_GAIN to " << api->GetOptionValue(Option::MAX_GAIN);
LOG(INFO) << "Set MAX_EXPOSURE_TIME to "
<< api->GetOptionValue(Option::MAX_EXPOSURE_TIME);
LOG(INFO) << "Set DESIRED_BRIGHTNESS to "
<< api->GetOptionValue(Option::DESIRED_BRIGHTNESS);
s2100/s210a：
auto &&api = API::Create(argc, argv);
bool ok;
auto &&request = api->SelectStreamRequest(&ok);
if (!ok) return 1;
api->ConfigStreamRequest(request);
// auto-exposure: 0
api->SetOptionValue(Option::EXPOSURE_MODE, 0);
// max_gain: range [0,255], default 8
api->SetOptionValue(Option::MAX_GAIN, 8);
// max_exposure_time: range [0,1000], default 333
api->SetOptionValue(Option::MAX_EXPOSURE_TIME, 333);
// desired_brightness: range [1,255], default 122
api->SetOptionValue(Option::DESIRED_BRIGHTNESS, 122);
// min_exposure_time: range [0,1000], default 0
api->SetOptionValue(Option::MIN_EXPOSURE_TIME, 0);
LOG(INFO) << "Enable auto-exposure";
LOG(INFO) << "Set EXPOSURE_MODE to "
<< api->GetOptionValue(Option::EXPOSURE_MODE);
LOG(INFO) << "Set MAX_GAIN to " << api->GetOptionValue(Option::MAX_GAIN);
LOG(INFO) << "Set MAX_EXPOSURE_TIME to "
<< api->GetOptionValue(Option::MAX_EXPOSURE_TIME);
LOG(INFO) << "Set DESIRED_BRIGHTNESS to "
<< api->GetOptionValue(Option::DESIRED_BRIGHTNESS);
LOG(INFO) << "Set MIN_EXPOSURE_TIME to "
<< api->GetOptionValue(Option::MIN_EXPOSURE_TIME);
参考运行结果，于 Linux 上：
s1030：
$ ./samples/_output/bin/tutorials/ctrl_auto_exposure
I0513 14:07:57.963943 31845 utils.cc:26] Detecting MYNT EYE devices
I0513 14:07:58.457536 31845 utils.cc:33] MYNT EYE devices:
I0513 14:07:58.457563 31845 utils.cc:37] index: 0, name: MYNT-EYE-S1000
I0513 14:07:58.457567 31845 utils.cc:43] Only one MYNT EYE device, select index: 0
I0513 14:07:58.474916 31845 auto_exposure.cc:37] Enable auto-exposure
I0513 14:07:58.491058 31845 auto_exposure.cc:38] Set MAX_GAIN to 48
I0513 14:07:58.505131 31845 auto_exposure.cc:39] Set MAX_EXPOSURE_TIME to 240
I0513 14:07:58.521375 31845 auto_exposure.cc:41] Set DESIRED_BRIGHTNESS to 192
s2100/s210a：
$ ./samples/_output/bin/tutorials/ctrl_auto_exposure
I/utils.cc:30 Detecting MYNT EYE devices
I/utils.cc:40 MYNT EYE devices:
I/utils.cc:43 index: 0, name: MYNT-EYE-S210A, sn: 07C41A190009071F
I/utils.cc:51 Only one MYNT EYE device, select index: 0
I/utils.cc:79 MYNT EYE devices:
I/utils.cc:82 index: 0, request: width: 1280, height: 400, format: Format::BGR888, fps: 10
I/utils.cc:82 index: 1, request: width: 1280, height: 400, format: Format::BGR888, fps: 20
I/utils.cc:82 index: 2, request: width: 1280, height: 400, format: Format::BGR888, fps: 30
I/utils.cc:82 index: 3, request: width: 1280, height: 400, format: Format::BGR888, fps: 60
I/utils.cc:82 index: 4, request: width: 2560, height: 800, format: Format::BGR888, fps: 10
I/utils.cc:82 index: 5, request: width: 2560, height: 800, format: Format::BGR888, fps: 20
I/utils.cc:82 index: 6, request: width: 2560, height: 800, format: Format::BGR888, fps: 30
I/utils.cc:93 There are 7 stream requests, select index:
3
I/auto_exposure.cc:72 Enable auto-exposure
I/auto_exposure.cc:73 Set EXPOSURE_MODE to 0
I/auto_exposure.cc:75 Set MAX_GAIN to 8
I/auto_exposure.cc:76 Set MAX_EXPOSURE_TIME to 333
I/auto_exposure.cc:78 Set DESIRED_BRIGHTNESS to 122
I/auto_exposure.cc:80 Set MIN_EXPOSURE_TIME to 0
样例程序会显示图像，左上角有真实曝光时间，单位毫秒。
完整代码样例，请见 auto_exposure.cc 。