From 73ab31021c59e1a0ffe7b0f0ca4fef45e2637646 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Sun, 9 Nov 2025 21:55:15 +0100
Subject: [PATCH] Add tin_json_to_tin_gpkg.py

---
 grid_tools/README.md               |  15 ++
 grid_tools/tin_json_to_tin_gpkg.py | 274 +++++++++++++++++++++++++++++
 2 files changed, 289 insertions(+)
 create mode 100755 grid_tools/tin_json_to_tin_gpkg.py

diff --git a/grid_tools/README.md b/grid_tools/README.md
index 28ca096..3008ecd 100644
--- a/grid_tools/README.md
+++ b/grid_tools/README.md
@@ -190,3 +190,18 @@ such as [gdal_translate](https://gdal.org/programs/gdal_translate.html) or
 [gdal_edit.py](https://gdal.org/programs/gdal_edit.html)
 
 Note: this script will not compress data. This must be done in a prior step.
+
+## Converting a TIN JSON file to a TIN GeoPackage file
+
+With the [tin_json_to_tin_gpkg.py](tin_json_to_tin_gpkg.py) script.
+
+Both formats may be used by the +proj=tinshift operation.
+
+Usage:
+```
+usage: tin_json_to_tin_gpkg.py [-h] source dest
+```
+
+See https://proj.org/en/latest/specifications/tin_json.html and
+https://proj.org/en/latest/specifications/tin_gpkg.html for the specification
+of both format.
diff --git a/grid_tools/tin_json_to_tin_gpkg.py b/grid_tools/tin_json_to_tin_gpkg.py
new file mode 100755
index 0000000..b92ecdd
--- /dev/null
+++ b/grid_tools/tin_json_to_tin_gpkg.py
@@ -0,0 +1,274 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+###############################################################################
+#
+# Project:  PROJ
+# Purpose:  Convert a TIN JSON to a TIN GeoPackage
+# Author:   Even Rouault <even.rouault at spatialys.com>
+#
+###############################################################################
+# Copyright (c) 2025, Even Rouault <even.rouault at spatialys.com>
+#
+# SPDX-License-Identifier: MIT
+###############################################################################
+
+import argparse
+import json
+import struct
+
+from osgeo import gdal, ogr, osr
+
+
+def get_args():
+    parser = argparse.ArgumentParser(
+        description="Convert a TIN JSON to a TIN GeoPackage."
+    )
+    parser.add_argument("source", help="Source JSON file")
+    parser.add_argument("dest", help="Destination GeoPackage file")
+    return parser.parse_args()
+
+
+def as_i32le_hex(v):
+    return "".join(["%02X" % b for b in struct.pack("<i", v)])
+
+
+def convert_json_to_gpkg(source, dest):
+
+    j = json.loads(open(source, "rb").read())
+
+    if "file_type" not in j:
+        raise Exception(f"'file_type' missing in {source}")
+    file_type = j["file_type"]
+    if file_type != "triangulation_file":
+        raise Exception(f"file_type={file_type} not handled")
+
+    if "vertices" not in j or not isinstance(j["vertices"], list):
+        raise Exception(f"'vertices' array missing in {source}")
+    vertices = j["vertices"]
+
+    if "vertices_columns" not in j or not isinstance(j["vertices_columns"], list):
+        raise Exception(f"'vertices_columns' array missing in {source}")
+    vertices_columns = j["vertices_columns"]
+    idx_source_x = vertices_columns.index("source_x")
+    idx_source_y = vertices_columns.index("source_y")
+
+    if "triangles" not in j or not isinstance(j["triangles"], list):
+        raise Exception(f"'triangles' array missing in {source}")
+    triangles = j["triangles"]
+
+    if "triangles_columns" not in j or not isinstance(j["triangles_columns"], list):
+        raise Exception(f"'triangles_columns' array missing in {source}")
+    triangles_columns = j["triangles_columns"]
+    idx_vertex1 = triangles_columns.index("idx_vertex1")
+    idx_vertex2 = triangles_columns.index("idx_vertex2")
+    idx_vertex3 = triangles_columns.index("idx_vertex3")
+
+    with gdal.config_options(
+        {
+            "OGR_SQLITE_PRAGMA": "page_size=1024",
+            "CREATE_TRIGGERS": "NO",
+            "CREATE_RASTER_TABLES": "NO",
+        }
+    ):
+        ds = gdal.GetDriverByName("GPKG").CreateVector(dest)
+    ds.StartTransaction()
+
+    srs = None
+    if "input_crs" in j:
+        srs = osr.SpatialReference()
+        srs.SetAxisMappingStrategy(osr.OAMS_TRADITIONAL_GIS_ORDER)
+        srs.SetFromUserInput(j["input_crs"])
+
+    metadata = {}
+    for key, value in j.items():
+        if key not in (
+            "vertices_columns",
+            "triangles_columns",
+            "vertices",
+            "triangles",
+        ):
+            metadata[key] = value
+
+    if "target_x" in vertices_columns and "target_y" in vertices_columns:
+        idx_target_x = vertices_columns.index("target_x")
+        idx_target_y = vertices_columns.index("target_y")
+
+        shift_x = [vertex[idx_target_x] - vertex[idx_source_x] for vertex in vertices]
+        shift_y = [vertex[idx_target_y] - vertex[idx_source_y] for vertex in vertices]
+        metadata["min_shift_x"] = min(shift_x)
+        metadata["max_shift_x"] = max(shift_x)
+        metadata["min_shift_y"] = min(shift_y)
+        metadata["max_shift_y"] = max(shift_y)
+
+    metadata["num_vertices"] = len(vertices)
+
+    ds.ExecuteSQL(
+        """CREATE TABLE gpkg_metadata (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  md_scope TEXT NOT NULL DEFAULT 'dataset',
+  md_standard_uri TEXT NOT NULL,
+  mime_type TEXT NOT NULL DEFAULT 'text/xml',
+  metadata TEXT NOT NULL DEFAULT ''
+)"""
+    )
+    ds.ExecuteSQL(
+        """CREATE TABLE gpkg_metadata_reference (
+  reference_scope TEXT NOT NULL,
+  table_name TEXT,
+  column_name TEXT,
+  row_id_value INTEGER,
+  timestamp DATETIME NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now')),
+  md_file_id INTEGER NOT NULL,
+  md_parent_id INTEGER,
+  CONSTRAINT crmr_mfi_fk FOREIGN KEY (md_file_id) REFERENCES gpkg_metadata(id),
+  CONSTRAINT crmr_mpi_fk FOREIGN KEY (md_parent_id) REFERENCES gpkg_metadata(id)
+)"""
+    )
+
+    serialized_json = json.dumps(metadata).replace("'", "''")
+    ds.ExecuteSQL(
+        f"INSERT INTO gpkg_metadata (id, md_scope, md_standard_uri, mime_type, metadata) VALUES (1, 'dataset', 'https://proj.org', 'application/json', '{serialized_json}')"
+    )
+    ds.ExecuteSQL(
+        "INSERT INTO gpkg_metadata_reference (reference_scope, table_name, column_name, row_id_value, md_file_id, md_parent_id) VALUES ('geopackage', NULL, NULL, NULL, 1, NULL)"
+    )
+
+    ds.ExecuteSQL("CREATE TABLE gpkg_extensions (table_name TEXT,column_name TEXT,extension_name TEXT NOT NULL,definition TEXT NOT NULL,scope TEXT NOT NULL,CONSTRAINT ge_tce UNIQUE (table_name, column_name, extension_name))")
+    ds.ExecuteSQL("INSERT INTO gpkg_extensions VALUES('gpkg_metadata', NULL, 'gpkg_metadata', 'http://www.geopackage.org/spec120/#extension_metadata', 'read-write')")
+    ds.ExecuteSQL("INSERT INTO gpkg_extensions VALUES('gpkg_metadata_reference', NULL, 'gpkg_metadata', 'http://www.geopackage.org/spec120/#extension_metadata', 'read-write')")
+
+    lyr = ds.CreateLayer(
+        "vertices",
+        geom_type=ogr.wkbPoint,
+        srs=srs,
+        options=["SPATIAL_INDEX=NO", "GEOMETRY_NULLABLE=NO"],
+    )
+
+    ogr_to_vertices_column_idx = []
+    for idx, col in enumerate(vertices_columns):
+        if idx in (idx_source_x, idx_source_y):
+            continue
+        is_reserved_col = col in (
+            "target_x",
+            "target_y",
+            "source_z",
+            "target_z",
+            "offset_z",
+        )
+        if isinstance(vertices[0][idx], float) or is_reserved_col:
+            ogr_type = ogr.OFTReal
+        elif isinstance(vertices[0][idx], int):
+            ogr_type = ogr.OFTInteger
+        else:
+            ogr_type = ogr.OFTString
+        fld_defn = ogr.FieldDefn(col, ogr_type)
+        if is_reserved_col:
+            fld_defn.SetNullable(False)
+        lyr.CreateField(fld_defn)
+        ogr_to_vertices_column_idx.append(idx)
+    for fid, v in enumerate(vertices):
+        f = ogr.Feature(lyr.GetLayerDefn())
+        for ogr_idx, idx in enumerate(ogr_to_vertices_column_idx):
+            f.SetField(ogr_idx, v[idx])
+        p = ogr.Geometry(ogr.wkbPoint)
+        p.SetPoint_2D(0, v[idx_source_x], v[idx_source_y])
+        f.SetGeometryDirectly(p)
+        f.SetFID(fid)
+        lyr.CreateFeature(f)
+
+    lyr = ds.CreateLayer("triangles_def", geom_type=ogr.wkbNone)
+    other_fields = ""
+    for idx, col in enumerate(triangles_columns):
+        if isinstance(triangles[0][idx], float):
+            ogr_type = ogr.OFTReal
+        elif isinstance(triangles[0][idx], int):
+            ogr_type = ogr.OFTInteger
+        else:
+            ogr_type = ogr.OFTString
+        fld_defn = ogr.FieldDefn(col, ogr_type)
+        if col in ("idx_vertex1", "idx_vertex2", "idx_vertex3"):
+            fld_defn.SetNullable(False)
+        lyr.CreateField(fld_defn)
+        other_fields += ", "
+        other_fields += col
+    for fid, triangle in enumerate(triangles):
+        f = ogr.Feature(lyr.GetLayerDefn())
+        for idx in range(len(triangles_columns)):
+            f.SetField(idx, triangle[idx])
+        f.SetFID(fid)
+        lyr.CreateFeature(f)
+
+    with ds.ExecuteSQL(
+        "SELECT srs_id FROM gpkg_contents WHERE table_name = 'vertices'"
+    ) as sql_lyr:
+        f = sql_lyr.GetNextFeature()
+        srs_id = f["srs_id"]
+
+    min_x = min([v[idx_source_x] for v in vertices])
+    max_x = max([v[idx_source_x] for v in vertices])
+    min_y = min([v[idx_source_y] for v in vertices])
+    max_y = max([v[idx_source_y] for v in vertices])
+
+    # We use a trick to generate GPKG polygon geometries from GPKG point geometries
+    # of the vertices.
+    srs_id_i32le = as_i32le_hex(srs_id)
+    wkb_polygon_i32le = as_i32le_hex(3)
+    number_rings_i32le = as_i32le_hex(1)
+    number_vertices_i32le = as_i32le_hex(4)
+    triangle_gpkg_prefix = f"47500001{srs_id_i32le}01{wkb_polygon_i32le}{number_rings_i32le}{number_vertices_i32le}"
+    # 14 = GPKG_header_size_without_envelope (8) + WKB point header (5) + base_one_index (1)
+    ds.ExecuteSQL(
+        f"CREATE VIEW triangles AS SELECT triangles_def.fid AS OGC_FID{other_fields}, CAST(X'{triangle_gpkg_prefix}' || substr(v1.geom, 14) || substr(v2.geom, 14) || substr(v3.geom, 14) || substr(v1.geom, 14) AS BLOB) AS geom FROM triangles_def LEFT JOIN vertices v1 ON idx_vertex1 = v1.fid LEFT JOIN vertices v2 ON idx_vertex2 = v2.fid LEFT JOIN vertices v3 ON idx_vertex3 = v3.fid"
+    )
+    ds.ExecuteSQL(
+        f"INSERT INTO gpkg_contents (table_name, identifier, data_type, srs_id, min_x, min_y, max_x, max_y) VALUES ('triangles', 'triangles', 'features', {srs_id}, {min_x}, {min_y}, {max_x}, {max_y})"
+    )
+    ds.ExecuteSQL(
+        f"INSERT INTO gpkg_geometry_columns (table_name, column_name, geometry_type_name, srs_id, z, m) values ('triangles', 'geom', 'POLYGON', {srs_id}, 0, 0)"
+    )
+
+    ds.ExecuteSQL(
+        "CREATE VIRTUAL TABLE rtree_triangles_geom USING rtree(id, minx, maxx, miny, maxy)"
+    )
+    for fid, triangle in enumerate(triangles):
+        v1 = vertices[triangle[idx_vertex1]]
+        v2 = vertices[triangle[idx_vertex2]]
+        v3 = vertices[triangle[idx_vertex3]]
+        tab_x = [v1[idx_source_x], v2[idx_source_x], v3[idx_source_x]]
+        tab_y = [v1[idx_source_y], v2[idx_source_y], v3[idx_source_y]]
+        minx = min(tab_x)
+        miny = min(tab_y)
+        maxx = max(tab_x)
+        maxy = max(tab_y)
+        ds.ExecuteSQL(
+            f"INSERT INTO rtree_triangles_geom VALUES ({fid}, {minx}, {maxx}, {miny}, {maxy})"
+        )
+
+    ds.CommitTransaction()
+    ds.ExecuteSQL("DELETE FROM sqlite_sequence")
+    ds.ExecuteSQL("DROP TRIGGER trigger_insert_feature_count_vertices")
+    ds.ExecuteSQL("DROP TRIGGER trigger_delete_feature_count_vertices")
+    ds.ExecuteSQL("DROP TRIGGER trigger_insert_feature_count_triangles_def")
+    ds.ExecuteSQL("DROP TRIGGER trigger_delete_feature_count_triangles_def")
+    ds.ExecuteSQL("DROP TABLE gpkg_ogr_contents")
+    ds.ExecuteSQL("VACUUM")
+    ds.Close()
+
+    # Check that the triangle coverage is OK (no overlaps)
+    if gdal.VersionInfo(None) >= "3120000":
+        with gdal.alg.vector.check_coverage(
+            input=dest, output="", output_format="MEM", input_layer="triangles"
+        ) as alg:
+            out_ds = alg.Output()
+            out_lyr = out_ds.GetLayer(0)
+            if out_lyr.GetFeatureCount():
+                print("Coverage of triangles has issues. Invalid edges:")
+                for f in out_lyr:
+                    f.DumpReadable()
+
+
+if __name__ == "__main__":
+
+    gdal.UseExceptions()
+    args = get_args()
+    convert_json_to_gpkg(args.source, args.dest)