diff --git a/aos/vision/blob/transpose.cc b/aos/vision/blob/transpose.cc
new file mode 100644
index 0000000..19ac965
--- /dev/null
+++ b/aos/vision/blob/transpose.cc
@@ -0,0 +1,87 @@
+#include "aos/vision/blob/transpose.h"
+
+#include <algorithm>
+
+namespace aos {
+namespace vision {
+
+RangeImage Transpose(const RangeImage &img) {
+  enum EventT {
+    // Must happen before point adds and deletes.
+    kRangeStart = 0,
+    kRangeEnd = 1,
+    // Non-overlapping
+    kPointAdd = 3,
+    kPointDel = 2,
+  };
+  std::vector<std::vector<std::pair<int, EventT>>> events;
+  int y = img.min_y();
+  for (const std::vector<ImageRange> &row : img) {
+    for (const ImageRange &range : row) {
+      if (range.ed >= static_cast<int>(events.size()))
+        events.resize(range.ed + 1);
+      events[range.st].emplace_back(y, kPointAdd);
+      events[range.ed].emplace_back(y, kPointDel);
+    }
+    ++y;
+  }
+
+  int min_y = 0;
+  while (min_y < (int)events.size() && events[min_y].empty()) ++min_y;
+
+  std::vector<ImageRange> prev_ranges;
+  std::vector<ImageRange> cur_ranges;
+
+  std::vector<std::vector<ImageRange>> rows;
+  for (int y = min_y; y < static_cast<int>(events.size()) - 1; ++y) {
+    auto row_events = std::move(events[y]);
+    for (const auto &range : prev_ranges) {
+      row_events.emplace_back(range.st, kRangeStart);
+      row_events.emplace_back(range.ed, kRangeEnd);
+    }
+    std::sort(row_events.begin(), row_events.end());
+    cur_ranges.clear();
+
+    bool has_cur_range = false;
+    ImageRange cur_range{0, 0};
+    auto add_range = [&](ImageRange range) {
+      if (range.st == range.ed) return;
+      if (has_cur_range) {
+        if (cur_range.ed == range.st) {
+          range = ImageRange{cur_range.st, range.ed};
+        } else {
+          cur_ranges.emplace_back(cur_range);
+        }
+      }
+      cur_range = range;
+      has_cur_range = true;
+    };
+
+    int prev_start;
+    for (const auto &pt : row_events) {
+      switch (pt.second) {
+        case kRangeStart:
+          prev_start = pt.first;
+          break;
+        case kPointAdd:
+          add_range(ImageRange{pt.first, pt.first + 1});
+          break;
+        case kRangeEnd:
+          add_range(ImageRange{prev_start, pt.first});
+          break;
+        case kPointDel:
+          add_range(ImageRange{prev_start, pt.first});
+          prev_start = pt.first + 1;
+          break;
+      }
+    }
+
+    if (has_cur_range) cur_ranges.emplace_back(cur_range);
+    rows.emplace_back(cur_ranges);
+    std::swap(cur_ranges, prev_ranges);
+  }
+  return RangeImage(min_y, std::move(rows));
+}
+
+}  // namespace vision
+}  // namespace aos