Merge pull request #8578 from OSGeo/backport-8567-to-release/3.7

[Backport release/3.7] MBTiles: BuildOverviews(): correctly set minzoom metadata (fixes #8565)
OSGeo · Oct 19, 2023 · 4731bad · 4731bad
2 parents f33e4f8 + 305e74d
commit 4731bad
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Showing 2 changed files with 87 additions and 30 deletions.
diff --git a/autotest/gdrivers/mbtiles.py b/autotest/gdrivers/mbtiles.py
@@ -435,6 +435,41 @@ def test_mbtiles_7():
     gdal.Unlink("/vsimem/mbtiles_7.mbtiles")
 
 
+###############################################################################
+# Test building overview
+
+
+@pytest.mark.require_driver("PNG")
+def test_mbtiles_overview_minzoom():
+
+    filename = "/vsimem/test_mbtiles_overview_minzoom.mbtiles"
+
+    gdal.Translate(filename, "data/byte.tif", options="-outsize 1024 0")
+    ds = gdal.Open(filename, gdal.GA_Update)
+    assert ds.GetMetadataItem("minzoom") == "17"
+    assert ds.GetMetadataItem("maxzoom") == "17"
+    ds.BuildOverviews("NEAR", [2])
+    ds = None
+
+    ds = gdal.Open(filename)
+    assert ds.GetRasterBand(1).GetOverviewCount() == 1
+    assert ds.GetMetadataItem("minzoom") == "16"
+    assert ds.GetMetadataItem("maxzoom") == "17"
+    ds = None
+
+    ds = gdal.Open(filename, gdal.GA_Update)
+    ds.BuildOverviews("NEAR", [8])
+    ds = None
+
+    ds = gdal.Open(filename)
+    assert ds.GetRasterBand(1).GetOverviewCount() == 3
+    assert ds.GetMetadataItem("minzoom") == "14"
+    assert ds.GetMetadataItem("maxzoom") == "17"
+    ds = None
+
+    gdal.Unlink(filename)
+
+
 ###############################################################################
 # Single band with 24 bit color table, PNG
 

diff --git a/frmts/mbtiles/mbtilesdataset.cpp b/frmts/mbtiles/mbtilesdataset.cpp
@@ -3539,15 +3539,14 @@ CPLErr MBTilesDataset::IBuildOverviews(
         int nRows = 0;
         int nCols = 0;
         char **papszResult = nullptr;
-        sqlite3_get_table(hDB, "SELECT * FROM metadata WHERE name = 'minzoom'",
-                          &papszResult, &nRows, &nCols, nullptr);
+        sqlite3_get_table(
+            hDB, "SELECT * FROM metadata WHERE name = 'minzoom' LIMIT 2",
+            &papszResult, &nRows, &nCols, nullptr);
         sqlite3_free_table(papszResult);
         if (nRows == 1)
         {
-            sqlite3_exec(hDB, "DELETE FROM metadata WHERE name = 'minzoom'",
-                         nullptr, nullptr, nullptr);
             pszSQL = sqlite3_mprintf(
-                "INSERT INTO metadata (name, value) VALUES ('minzoom', '%d')",
+                "UPDATE metadata SET value = %d WHERE name = 'minzoom'",
                 m_nZoomLevel);
             sqlite3_exec(hDB, pszSQL, nullptr, nullptr, nullptr);
             sqlite3_free(pszSQL);
@@ -3572,6 +3571,18 @@ CPLErr MBTilesDataset::IBuildOverviews(
     }
 
     FlushCache(false);
+
+    const auto GetOverviewIndex = [](int nVal)
+    {
+        int iOvr = -1;
+        while (nVal > 1)
+        {
+            nVal >>= 1;
+            iOvr++;
+        }
+        return iOvr;
+    };
+
     for (int i = 0; i < nOverviews; i++)
     {
         if (panOverviewList[i] < 2)
@@ -3588,40 +3599,34 @@ CPLErr MBTilesDataset::IBuildOverviews(
                      panOverviewList[i]);
             return CE_Failure;
         }
+        const int iOvr = GetOverviewIndex(panOverviewList[i]);
+        if (iOvr >= m_nOverviewCount)
+        {
+            CPLDebug("MBTILES",
+                     "Requested overview factor %d leads to too small overview "
+                     "and will be ignored",
+                     panOverviewList[i]);
+        }
     }
 
     GDALRasterBand ***papapoOverviewBands =
         (GDALRasterBand ***)CPLCalloc(sizeof(void *), nBands);
     int iCurOverview = 0;
-    int nMinZoom = m_nZoomLevel;
-    for (int i = 0; i < m_nOverviewCount; i++)
-    {
-        MBTilesDataset *poODS = m_papoOverviewDS[i];
-        if (poODS->m_nZoomLevel < nMinZoom)
-            nMinZoom = poODS->m_nZoomLevel;
-    }
     for (int iBand = 0; iBand < nBands; iBand++)
     {
         papapoOverviewBands[iBand] =
             (GDALRasterBand **)CPLCalloc(sizeof(void *), nOverviews);
         iCurOverview = 0;
         for (int i = 0; i < nOverviews; i++)
         {
-            int nVal = panOverviewList[i];
-            int iOvr = -1;
-            while (nVal > 1)
-            {
-                nVal >>= 1;
-                iOvr++;
-            }
-            if (iOvr >= m_nOverviewCount)
+            const int iOvr = GetOverviewIndex(panOverviewList[i]);
+            if (iOvr < m_nOverviewCount)
             {
-                continue;
+                MBTilesDataset *poODS = m_papoOverviewDS[iOvr];
+                papapoOverviewBands[iBand][iCurOverview] =
+                    poODS->GetRasterBand(iBand + 1);
+                iCurOverview++;
             }
-            MBTilesDataset *poODS = m_papoOverviewDS[iOvr];
-            papapoOverviewBands[iBand][iCurOverview] =
-                poODS->GetRasterBand(iBand + 1);
-            iCurOverview++;
         }
     }
 
@@ -3637,19 +3642,36 @@ CPLErr MBTilesDataset::IBuildOverviews(
 
     if (eErr == CE_None)
     {
+        // Determine new minzoom value from the existing one and the new
+        // requested overview levels
+        int nMinZoom = m_nZoomLevel;
+        bool bHasMinZoomMetadata = false;
         int nRows = 0;
         int nCols = 0;
         char **papszResult = nullptr;
         sqlite3_get_table(
-            hDB, "SELECT * FROM metadata WHERE name = 'minzoom' LIMIT 2",
+            hDB, "SELECT value FROM metadata WHERE name = 'minzoom' LIMIT 2",
             &papszResult, &nRows, &nCols, nullptr);
+        if (nRows == 1 && nCols == 1 && papszResult[1])
+        {
+            bHasMinZoomMetadata = true;
+            nMinZoom = atoi(papszResult[1]);
+        }
         sqlite3_free_table(papszResult);
-        if (nRows == 1)
+        if (bHasMinZoomMetadata)
         {
-            sqlite3_exec(hDB, "DELETE FROM metadata WHERE name = 'minzoom'",
-                         nullptr, nullptr, nullptr);
+            for (int i = 0; i < nOverviews; i++)
+            {
+                const int iOvr = GetOverviewIndex(panOverviewList[i]);
+                if (iOvr < m_nOverviewCount)
+                {
+                    const MBTilesDataset *poODS = m_papoOverviewDS[iOvr];
+                    nMinZoom = std::min(nMinZoom, poODS->m_nZoomLevel);
+                }
+            }
+
             char *pszSQL = sqlite3_mprintf(
-                "INSERT INTO metadata (name, value) VALUES ('minzoom', '%d')",
+                "UPDATE metadata SET value = '%d' WHERE name = 'minzoom'",
                 nMinZoom);
             sqlite3_exec(hDB, pszSQL, nullptr, nullptr, nullptr);
             sqlite3_free(pszSQL);