diff --git a/y2017/vision/debug_viewer.cc b/y2017/vision/debug_viewer.cc
new file mode 100644
index 0000000..83f306f
--- /dev/null
+++ b/y2017/vision/debug_viewer.cc
@@ -0,0 +1,129 @@
+#include <Eigen/Dense>
+#include <iostream>
+
+#include "y2017/vision/target_finder.h"
+
+#include "aos/vision/blob/move_scale.h"
+#include "aos/vision/blob/stream_view.h"
+#include "aos/vision/blob/transpose.h"
+#include "aos/vision/debug/debug_framework.h"
+#include "aos/vision/math/vector.h"
+
+using aos::vision::ImageRange;
+using aos::vision::ImageFormat;
+using aos::vision::RangeImage;
+using aos::vision::BlobList;
+
+namespace y2017 {
+namespace vision {
+
+BlobList RenderTargetListShifted(const std::vector<TargetComponent> &list) {
+  BlobList out;
+  for (const auto &entity : list) {
+    out.emplace_back(entity.RenderShifted());
+  }
+  return out;
+}
+
+RangeImage TargetComponent::RenderShifted() const {
+  std::vector<std::vector<ImageRange>> out_range_list;
+  int y = 0;
+  double max_y = -b / (2 * a);
+  double parab_off = max_y * max_y * a + max_y * b;
+  RangeImage t_img = Transpose(*img);
+  for (const auto &row : t_img) {
+    int off = -(y * y * a + y * b - parab_off);
+    // int off = 0;
+    // fprintf(stderr, "off: %d %d\n", off, y);
+    std::vector<ImageRange> row_out;
+    for (const ImageRange &range : row) {
+      row_out.emplace_back(ImageRange{off + range.st, off + range.ed});
+    }
+    ++y;
+    out_range_list.emplace_back(std::move(row_out));
+  }
+  return RangeImage(t_img.min_y(), std::move(out_range_list));
+}
+
+class FilterHarnessExample : public aos::vision::FilterHarness {
+ public:
+  aos::vision::RangeImage Threshold(aos::vision::ImagePtr image) override {
+    return finder_.Threshold(image);
+  }
+
+  void InstallViewer(aos::vision::BlobStreamViewer *viewer) override {
+    viewer_ = viewer;
+    viewer_->SetScale(0.5);
+    overlays_.push_back(&overlay_);
+    overlays_.push_back(finder_.GetOverlay());
+    viewer_->view()->SetOverlays(&overlays_);
+  }
+
+  bool HandleBlobs(BlobList imgs, ImageFormat /*fmt*/) override {
+    // reset for next drawing cycle
+    for (auto &overlay : overlays_) {
+      overlay->Reset();
+    }
+
+    // Remove bad blobs.
+    finder_.PreFilter(imgs);
+
+    // calculate each component/
+    std::vector<TargetComponent> target_component_list =
+        finder_.FillTargetComponentList(imgs);
+
+    DrawComponents(target_component_list);
+
+    // Put the compenents together into targets and pick the best.
+    Target final_target;
+    bool found_target =
+        finder_.FindTargetFromComponents(target_component_list, &final_target);
+
+    // BlobList newImg = RenderTargetListShifted(target_component_list);
+    if (viewer_) {
+      viewer_->DrawBlobList(imgs, {0, 0, 255});
+    }
+
+    if (found_target) {
+      BlobList list;
+      list.emplace_back(*(final_target.comp1.img));
+      list.emplace_back(*(final_target.comp2.img));
+      viewer_->DrawBlobList(list, {0, 255, 0});
+      overlay_.DrawCross(final_target.screen_coord, 25, {255, 255, 255});
+    }
+
+    // No targets.
+    return found_target;
+  }
+
+  void DrawComponents(const std::vector<TargetComponent> comp) {
+    for (const TargetComponent &t : comp) {
+      aos::vision::ImageBBox bbox;
+      GetBBox(*(t.img), &bbox);
+      overlay_.DrawBBox(bbox, {255, 0, 0});
+
+      overlay_.StartNewProfile();
+      for (int i = 0; i < bbox.maxx - bbox.minx; i += 10) {
+        double y0 = t.a * i * i + t.b * i + t.c_0;
+        double y1 = t.a * i * i + t.b * i + t.c_1;
+        overlay_.AddPoint(aos::vision::Vector<2>(i + t.mini, y0), {255, 0, 0});
+        overlay_.AddPoint(aos::vision::Vector<2>(i + t.mini, y1), {255, 0, 0});
+      }
+    }
+  }
+
+ private:
+  // implementation of the filter pipeline.
+  TargetFinder finder_;
+  aos::vision::BlobStreamViewer *viewer_ = nullptr;
+  aos::vision::PixelLinesOverlay overlay_;
+  std::vector<aos::vision::OverlayBase *> overlays_;
+};
+
+}  // namespace vision
+}  // namespace y2017
+
+int main(int argc, char **argv) {
+  y2017::vision::FilterHarnessExample filter_harness;
+  aos::vision::DebugFrameworkMain(argc, argv, &filter_harness);
+}