Auto Exposure:

  - Filter results down to the three best.
  - Changing exposure based on distance to the target or at random.
  - Plumb exposure through the debug framework.
  - Refactor into target finder.

Change-Id: Ia083f56859938bf0825472fd15d248c545f6f2fc
diff --git a/aos/vision/image/image_stream.h b/aos/vision/image/image_stream.h
index 57e06cb..8aab97d 100644
--- a/aos/vision/image/image_stream.h
+++ b/aos/vision/image/image_stream.h
@@ -37,6 +37,11 @@
 
   void ReadEvent() override { reader_->HandleFrame(); }
 
+  bool SetExposure(int abs_exp) {
+    return reader_->SetCameraControl(V4L2_CID_EXPOSURE_ABSOLUTE,
+                                     "V4L2_CID_EXPOSURE_ABSOLUTE", abs_exp);
+  }
+
  private:
   void ProcessHelper(DataRef data, aos::monotonic_clock::time_point timestamp);