diff --git a/aos/vision/blob/threshold.h b/aos/vision/blob/threshold.h
new file mode 100644
index 0000000..8b6051f
--- /dev/null
+++ b/aos/vision/blob/threshold.h
@@ -0,0 +1,40 @@
+#ifndef _AOS_VIISON_BLOB_THRESHOLD_H_
+#define _AOS_VIISON_BLOB_THRESHOLD_H_
+
+#include "aos/vision/blob/range_image.h"
+#include "aos/vision/image/image_types.h"
+
+namespace aos {
+namespace vision {
+
+// ThresholdFn should be a lambda.
+template <typename ThresholdFn>
+RangeImage DoThreshold(const ImagePtr &img, ThresholdFn &&fn) {
+  std::vector<std::vector<ImageRange>> ranges;
+  ranges.reserve(img.fmt().h);
+  for (int y = 0; y < img.fmt().h; ++y) {
+    bool p_score = false;
+    int pstart = -1;
+    std::vector<ImageRange> rngs;
+    for (int x = 0; x < img.fmt().w; ++x) {
+      if (fn(img.get_px(x, y)) != p_score) {
+        if (p_score) {
+          rngs.emplace_back(ImageRange(pstart, x));
+        } else {
+          pstart = x;
+        }
+        p_score = !p_score;
+      }
+    }
+    if (p_score) {
+      rngs.emplace_back(ImageRange(pstart, img.fmt().w));
+    }
+    ranges.push_back(rngs);
+  }
+  return RangeImage(0, std::move(ranges));
+}
+
+}  // namespace vision
+}  // namespace aos
+
+#endif  //  _AOS_VIISON_BLOB_THRESHOLD_H_