Merge pull request #8690 from rouault/vrt_approx_stats

VRTSourcedRasterBand: serialize approximate statistics inside .vrt when there are overviews
OSGeo · Nov 13, 2023 · 8e42f75 · 8e42f75
2 parents 65af0b8 + 7bd5c5e
commit 8e42f75
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Showing 2 changed files with 41 additions and 3 deletions.
diff --git a/autotest/gcore/vrt_read.py b/autotest/gcore/vrt_read.py
@@ -2535,3 +2535,32 @@ def test_vrt_read_complex_source_nodata_out_of_range(tmp_vsimem, data_type):
     got_data = vrt_ds.ReadRaster(buf_type=data_type)
     got_data = struct.unpack(array_type, got_data)
     assert got_data == (1,)
+
+
+###############################################################################
+# Test serialization of approximate ComputeStatistics() when there is
+# external overview
+
+
+def test_vrt_read_compute_statistics_approximate(tmp_vsimem):
+
+    gtiff_filename = str(tmp_vsimem / "tmp.tif")
+    gdal.Translate(
+        gtiff_filename, gdal.Open("data/byte.tif"), format="GTiff", width=256
+    )
+    vrt_filename = str(tmp_vsimem / "tmp.vrt")
+    gdal.Translate(vrt_filename, gtiff_filename)
+    ds = gdal.Open(vrt_filename)
+    ds.BuildOverviews("NEAR", [2])
+    ds = None
+    ds = gdal.Open(vrt_filename)
+    ds.GetRasterBand(1).ComputeStatistics(True)
+    ds = None
+    ds = gdal.Open(vrt_filename)
+    md = ds.GetRasterBand(1).GetMetadata()
+    assert md["STATISTICS_APPROXIMATE"] == "YES"
+    assert "STATISTICS_MINIMUM" in md
+    assert "STATISTICS_MAXIMUM" in md
+    assert "STATISTICS_MEAN" in md
+    assert "STATISTICS_STDDEV" in md
+    assert md["STATISTICS_VALID_PERCENT"] == "100"
diff --git a/frmts/vrt/vrtsourcedrasterband.cpp b/frmts/vrt/vrtsourcedrasterband.cpp
@@ -1233,23 +1233,32 @@ CPLErr VRTSourcedRasterBand::ComputeStatistics(int bApproxOK, double *pdfMin,
         if (poBand != nullptr && poBand != this)
         {
             auto l_poDS = dynamic_cast<VRTDataset *>(poDS);
+            CPLErr eErr;
             if (l_poDS && !l_poDS->m_apoOverviews.empty() &&
                 dynamic_cast<VRTSourcedRasterBand *>(poBand) != nullptr)
             {
                 auto apoTmpOverviews = std::move(l_poDS->m_apoOverviews);
                 l_poDS->m_apoOverviews.clear();
-                auto eErr = poBand->GDALRasterBand::ComputeStatistics(
+                eErr = poBand->GDALRasterBand::ComputeStatistics(
                     TRUE, pdfMin, pdfMax, pdfMean, pdfStdDev, pfnProgress,
                     pProgressData);
                 l_poDS->m_apoOverviews = std::move(apoTmpOverviews);
-                return eErr;
             }
             else
             {
-                return poBand->ComputeStatistics(TRUE, pdfMin, pdfMax, pdfMean,
+                eErr = poBand->ComputeStatistics(TRUE, pdfMin, pdfMax, pdfMean,
                                                  pdfStdDev, pfnProgress,
                                                  pProgressData);
             }
+            if (eErr == CE_None && pdfMin && pdfMax && pdfMean && pdfStdDev)
+            {
+                SetMetadataItem("STATISTICS_APPROXIMATE", "YES");
+                SetMetadataItem(
+                    "STATISTICS_VALID_PERCENT",
+                    poBand->GetMetadataItem("STATISTICS_VALID_PERCENT"));
+                SetStatistics(*pdfMin, *pdfMax, *pdfMean, *pdfStdDev);
+            }
+            return eErr;
         }
     }