Added cameraconv.py helper

This python program converts from Splat_vins cam_pos.txt file format to
the camers.json format expected by splatapult.

cameraconv.py

@@ -0,0 +1,66 @@
+# convert cam_pose.txt format into camera.json format.
+
+# Timestamp, x,y,z,qx,qy,qz,qw
+
+from collections import namedtuple
+import io
+import json
+
+import numpy as np
+import quaternion  # pip install numpy-quaternion
+
+def quat_to_mat(qx, qy, qz, qw):
+    q = np.quaternion(qw, qx, qy, qz)
+    return quaternion.as_rotation_matrix(q).tolist()
+
+"""
+inline Matrix<Scalar> Matrix<Scalar>::FromQuat(const Quat<Scalar>& q)
+{
+    Matrix<Scalar> m;
+    m.SetXAxis(q.Rotate(Vector3<Scalar>(1, 0, 0)));
+    m.SetYAxis(q.Rotate(Vector3<Scalar>(0, 1, 0)));
+    m.SetZAxis(q.Rotate(Vector3<Scalar>(0, 0, 1)));
+    m.SetTrans(Vector3<Scalar>(0, 0, 0));
+    return m;
+}
+"""
+
+Camera = namedtuple("Camera", ["timestamp", "x", "y", "z", "qx", "qy", "qz", "qw"])
+
+cameras = []
+with open("cam_pose.txt", "r") as f:
+    for line in f:
+        if line.strip():  # Check if the line is not empty
+            fields = line.strip().split(" ")
+            record = Camera(
+                timestamp=float(fields[0]),
+                x=float(fields[1]),
+                y=float(fields[2]),
+                z=float(fields[3]),
+                qx=float(fields[4]),
+                qy=float(fields[5]),
+                qz=float(fields[6]),
+                qw=float(fields[7]),
+            )
+            cameras.append(record)
+
+objs = []
+i = 0
+for cam in cameras:
+    objs.append(
+        {
+            "id": i,
+            "img_name": str(i),
+            "timestamp": cam.timestamp,
+            "width": 1920,
+            "height": 480,
+            "position": [cam.x, cam.y, cam.z],
+            "rotation": quat_to_mat(cam.qx, cam.qy, cam.qz, cam.qw),
+            "fx": 1000.0,
+            "fy": 1000.0,
+        }
+    )
+    i = i + 1
+
+with open("cameras.json", "w") as f:
+    f.write(json.dumps(objs, indent=2))