VRT: fix reading from virtual overviews when SrcRect / DstRect elemen…

…ts are missing
rouault · Aug 12, 2024 · dc1b3f3 · dc1b3f3
1 parent 151e0e8
commit dc1b3f3
Show file tree

Hide file tree

Showing 2 changed files with 53 additions and 4 deletions.
diff --git a/autotest/gcore/vrt_read.py b/autotest/gcore/vrt_read.py
@@ -851,6 +851,36 @@ def test_vrt_read_21():
     gdal.Unlink("/vsimem/byte.tif")
 
 
+###############################################################################
+# Test implicit virtual overviews
+
+
+def test_vrt_read_virtual_overview_no_srcrect_dstrect(tmp_vsimem):
+
+    ds = gdal.Open("data/byte.tif")
+    data = ds.ReadRaster(0, 0, 20, 20, 400, 400)
+    ds = None
+    tmp_tif = str(tmp_vsimem / "tmp.tif")
+    ds = gdal.GetDriverByName("GTiff").Create(tmp_tif, 400, 400)
+    ds.WriteRaster(0, 0, 400, 400, data)
+    ds.BuildOverviews("NEAR", [2])
+    ref_cs = ds.GetRasterBand(1).GetOverview(0).Checksum()
+    ds = None
+
+    ds = gdal.Open(
+        f"""<VRTDataset rasterXSize="400" rasterYSize="400">
+  <VRTRasterBand dataType="Byte" band="1">
+    <SimpleSource>
+      <SourceFilename>{tmp_tif}</SourceFilename>
+      <SourceBand>1</SourceBand>
+    </SimpleSource>
+  </VRTRasterBand>
+</VRTDataset>"""
+    )
+    assert ds.GetRasterBand(1).GetOverviewCount() == 1
+    assert ds.GetRasterBand(1).GetOverview(0).Checksum() == ref_cs
+
+
 ###############################################################################
 # Test that we honour NBITS with SimpleSource and ComplexSource
 

diff --git a/frmts/vrt/vrtsources.cpp b/frmts/vrt/vrtsources.cpp
@@ -114,15 +114,34 @@ VRTSimpleSource::VRTSimpleSource(const VRTSimpleSource *poSrcSource,
       m_dfSrcYOff(poSrcSource->m_dfSrcYOff),
       m_dfSrcXSize(poSrcSource->m_dfSrcXSize),
       m_dfSrcYSize(poSrcSource->m_dfSrcYSize),
-      m_dfDstXOff(poSrcSource->m_dfDstXOff * dfXDstRatio),
-      m_dfDstYOff(poSrcSource->m_dfDstYOff * dfYDstRatio),
-      m_dfDstXSize(poSrcSource->m_dfDstXSize * dfXDstRatio),
-      m_dfDstYSize(poSrcSource->m_dfDstYSize * dfYDstRatio),
       m_nMaxValue(poSrcSource->m_nMaxValue), m_bRelativeToVRTOri(-1),
       m_nExplicitSharedStatus(poSrcSource->m_nExplicitSharedStatus),
       m_osSrcDSName(poSrcSource->m_osSrcDSName),
       m_bDropRefOnSrcBand(poSrcSource->m_bDropRefOnSrcBand)
 {
+    if (!poSrcSource->IsSrcWinSet() && !poSrcSource->IsDstWinSet() &&
+        (dfXDstRatio != 1.0 || dfYDstRatio != 1.0))
+    {
+        auto l_band = GetRasterBand();
+        if (l_band)
+        {
+            m_dfSrcXOff = 0;
+            m_dfSrcYOff = 0;
+            m_dfSrcXSize = l_band->GetXSize();
+            m_dfSrcYSize = l_band->GetYSize();
+            m_dfDstXOff = 0;
+            m_dfDstYOff = 0;
+            m_dfDstXSize = l_band->GetXSize() * dfXDstRatio;
+            m_dfDstYSize = l_band->GetYSize() * dfYDstRatio;
+        }
+    }
+    else if (poSrcSource->IsDstWinSet())
+    {
+        m_dfDstXOff = poSrcSource->m_dfDstXOff * dfXDstRatio;
+        m_dfDstYOff = poSrcSource->m_dfDstYOff * dfYDstRatio;
+        m_dfDstXSize = poSrcSource->m_dfDstXSize * dfXDstRatio;
+        m_dfDstYSize = poSrcSource->m_dfDstYSize * dfYDstRatio;
+    }
 }
 
 /************************************************************************/