From cd728bdaead5954d51bde0bab849c8f10ab89d04 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Mon, 27 Jan 2025 16:28:48 +0100
Subject: [PATCH] gdalbuildvrt: add '-resolution same' mode to check all source
 rasters have the same resolution

---
 apps/gdalbuildvrt_lib.cpp            | 25 +++++++++++++++++++++++--
 doc/source/programs/gdalbuildvrt.rst |  8 +++++---
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/apps/gdalbuildvrt_lib.cpp b/apps/gdalbuildvrt_lib.cpp
index 43441e18c052..2491fcbab006 100644
--- a/apps/gdalbuildvrt_lib.cpp
+++ b/apps/gdalbuildvrt_lib.cpp
@@ -63,6 +63,7 @@ typedef enum
     LOWEST_RESOLUTION,
     HIGHEST_RESOLUTION,
     AVERAGE_RESOLUTION,
+    SAME_RESOLUTION,
     USER_RESOLUTION
 } ResolutionStrategy;
 
@@ -985,6 +986,23 @@ std::string VRTBuilder::AnalyseRaster(GDALDatasetH hDS,
             ns_res += dfDelta / nCountValid;
         }
     }
+    else if (resolutionStrategy == SAME_RESOLUTION)
+    {
+        if (bFirst)
+        {
+            we_res = padfGeoTransform[GEOTRSFRM_WE_RES];
+            ns_res = padfGeoTransform[GEOTRSFRM_NS_RES];
+        }
+        else if (we_res != padfGeoTransform[GEOTRSFRM_WE_RES] ||
+                 ns_res != padfGeoTransform[GEOTRSFRM_NS_RES])
+        {
+            return CPLSPrintf("Dataset %s has resolution %f x %f, whereas "
+                              "previous sources have resolution %f x %f",
+                              dsFileName, padfGeoTransform[GEOTRSFRM_WE_RES],
+                              padfGeoTransform[GEOTRSFRM_NS_RES], we_res,
+                              ns_res);
+        }
+    }
     else if (resolutionStrategy != USER_RESOLUTION)
     {
         if (bFirst)
@@ -1922,6 +1940,8 @@ GDALDatasetH GDALBuildVRT(const char *pszDest, int nSrcCount,
         eStrategy = HIGHEST_RESOLUTION;
     else if (EQUAL(sOptions.osResolution.c_str(), "lowest"))
         eStrategy = LOWEST_RESOLUTION;
+    else if (EQUAL(sOptions.osResolution.c_str(), "same"))
+        eStrategy = SAME_RESOLUTION;
 
     /* If -srcnodata is specified, use it as the -vrtnodata if the latter is not
      */
@@ -2055,7 +2075,7 @@ GDALBuildVRTOptionsGetParser(GDALBuildVRTOptions *psOptions,
                 "the default value which is 'location'."));
 
     argParser->add_argument("-resolution")
-        .metavar("user|average|highest|lowest")
+        .metavar("user|average|highest|lowest|same")
         .action(
             [psOptions](const std::string &s)
             {
@@ -2063,7 +2083,8 @@ GDALBuildVRTOptionsGetParser(GDALBuildVRTOptions *psOptions,
                 if (!EQUAL(psOptions->osResolution.c_str(), "user") &&
                     !EQUAL(psOptions->osResolution.c_str(), "average") &&
                     !EQUAL(psOptions->osResolution.c_str(), "highest") &&
-                    !EQUAL(psOptions->osResolution.c_str(), "lowest"))
+                    !EQUAL(psOptions->osResolution.c_str(), "lowest") &&
+                    !EQUAL(psOptions->osResolution.c_str(), "same"))
                 {
                     throw std::invalid_argument(
                         CPLSPrintf("Illegal resolution value (%s).",
diff --git a/doc/source/programs/gdalbuildvrt.rst b/doc/source/programs/gdalbuildvrt.rst
index 26fcd5122e54..e8c66f6006f8 100644
--- a/doc/source/programs/gdalbuildvrt.rst
+++ b/doc/source/programs/gdalbuildvrt.rst
@@ -19,8 +19,8 @@ Synopsis
                 [--quiet]
                 [[-strict]|[-non_strict]]
                 [-tile_index <field_name>]
-                [-resolution user|average|highest|lowest] [-tr <xres> <yes>]
-                [-input_file_list <filename>] [-separate]
+                [-resolution user|average|highest|lowest|same]
+                [-tr <xres> <yes>] [-input_file_list <filename>] [-separate]
                 [-allow_projection_difference] [-sd <n>] [-tap]
                 [-te <xmin> <ymin> <xmax> <ymax>] [-addalpha] [-b <band>]...
                 [-hidenodata] [-overwrite]
@@ -79,7 +79,7 @@ changed in later versions.
     Use the specified value as the tile index field, instead of the default
     value which is 'location'.
 
-.. option:: -resolution {highest|lowest|average|user}
+.. option:: -resolution {highest|lowest|average|user|same}
 
     In case the resolution of all input files is not the same, the :option:`-resolution` flag
     enables the user to control the way the output resolution is computed.
@@ -92,6 +92,8 @@ changed in later versions.
 
     `user` must be used in combination with the :option:`-tr` option to specify the target resolution.
 
+    `same` (added in GDAL 3.11) checks that all source rasters have the same resolution and errors out when this is not the case.
+
 .. option:: -tr <xres> <yres>
 
     Set target resolution. The values must be expressed in georeferenced units.