Merge pull request #10833 from rouault/deferred_warped_vrt_overview

Warped VRT: instantiate overview bands in a lazy fashion for faster execution
OSGeo · Sep 27, 2024 · 725739a · 725739a
2 parents caf4b54 + c558e98
commit 725739a
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Showing 3 changed files with 478 additions and 184 deletions.
diff --git a/autotest/gdrivers/vrtwarp.py b/autotest/gdrivers/vrtwarp.py
@@ -100,6 +100,12 @@ def test_vrtwarp_4():
     tmp_ds.BuildOverviews("NONE", overviewlist=[2, 4])
     tmp_ds.GetRasterBand(1).GetOverview(0).Fill(127)
     cs_ov0 = tmp_ds.GetRasterBand(1).GetOverview(0).Checksum()
+    data_ov0 = tmp_ds.GetRasterBand(1).GetOverview(0).ReadRaster()
+    data_ov0_subsampled = (
+        tmp_ds.GetRasterBand(1)
+        .GetOverview(0)
+        .ReadRaster(0, 0, 10, 10, 9, 9, resample_alg=gdal.GRIORA_Bilinear)
+    )
     tmp_ds.GetRasterBand(1).GetOverview(1).Fill(255)
     cs_ov1 = tmp_ds.GetRasterBand(1).GetOverview(1).Checksum()
 
@@ -109,6 +115,8 @@ def test_vrtwarp_4():
     for i in range(3):
         assert vrtwarp_ds.GetRasterBand(1).GetOverviewCount() == 2
         assert vrtwarp_ds.GetRasterBand(1).Checksum() == cs_main, i
+        assert vrtwarp_ds.GetRasterBand(1).GetOverview(-1) is None
+        assert vrtwarp_ds.GetRasterBand(1).GetOverview(2) is None
         assert vrtwarp_ds.GetRasterBand(1).GetOverview(0).Checksum() == cs_ov0
         assert vrtwarp_ds.GetRasterBand(1).GetOverview(1).Checksum() == cs_ov1
         if i == 0:
@@ -136,6 +144,13 @@ def test_vrtwarp_4():
     assert vrtwarp_ds.GetRasterBand(1).GetOverviewCount() == 3
     assert vrtwarp_ds.GetRasterBand(1).Checksum() == cs_main
     assert vrtwarp_ds.GetRasterBand(1).GetOverview(0).Checksum() == cs_ov0
+    assert vrtwarp_ds.GetRasterBand(1).ReadRaster(0, 0, 20, 20, 10, 10) == data_ov0
+    assert (
+        vrtwarp_ds.GetRasterBand(1).ReadRaster(
+            0, 0, 20, 20, 9, 9, resample_alg=gdal.GRIORA_Bilinear
+        )
+        == data_ov0_subsampled
+    )
     assert vrtwarp_ds.GetRasterBand(1).GetOverview(1).Checksum() == cs_ov1
     assert vrtwarp_ds.GetRasterBand(1).GetOverview(2).Checksum() == expected_cs_ov2
     vrtwarp_ds = None

diff --git a/frmts/vrt/vrtdataset.h b/frmts/vrt/vrtdataset.h
@@ -501,10 +501,16 @@ class CPL_DLL VRTWarpedDataset final : public VRTDataset
 {
     GDALWarpOperation *m_poWarper;
 
-    int m_nOverviewCount;
-    VRTWarpedDataset **m_papoOverviews;
+    bool m_bIsOverview = false;
+    std::vector<VRTWarpedDataset *> m_apoOverviews{};
     int m_nSrcOvrLevel;
 
+    bool GetOverviewSize(GDALDataset *poSrcDS, int iOvr, int iSrcOvr,
+                         int &nOvrXSize, int &nOvrYSize, double &dfSrcRatioX,
+                         double &dfSrcRatioY, double &dfTargetRatio) const;
+    int GetOverviewCount() const;
+    int GetSrcOverviewLevel(int iOvr, bool &bThisLevelOnlyOut) const;
+    VRTWarpedDataset *CreateImplicitOverview(int iOvr) const;
     void CreateImplicitOverviews();
 
     friend class VRTWarpedRasterBand;
@@ -1108,6 +1114,10 @@ class CPL_DLL VRTWarpedRasterBand final : public VRTRasterBand
   private:
     int m_nIRasterIOCounter =
         0;  //! Protects against infinite recursion inside IRasterIO()
+
+    int GetBestOverviewLevel(int &nXOff, int &nYOff, int &nXSize, int &nYSize,
+                             int nBufXSize, int nBufYSize,
+                             GDALRasterIOExtraArg *psExtraArg) const;
 };
 
 /************************************************************************/