From 16868463a1363a63fe89542ea7fa2a254838783f Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Wed, 23 Oct 2019 15:22:40 +0200
Subject: [PATCH] JPEG: fix further calls to RasterIO after reading full image
 at full resolution (fixes #1947)

---
 autotest/gdrivers/jpeg.py      | 8 ++++++++
 gdal/frmts/jpeg/jpgdataset.cpp | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/autotest/gdrivers/jpeg.py b/autotest/gdrivers/jpeg.py
index dd0d516b0266..dcfb53919836 100755
--- a/autotest/gdrivers/jpeg.py
+++ b/autotest/gdrivers/jpeg.py
@@ -796,8 +796,15 @@ def test_jpeg_23():
     assert cs == got_cs
 
     # Pixel interleaved
+    ds = gdal.Open('data/albania.jpg')
     data = ds.ReadRaster(0, 0, ds.RasterXSize, ds.RasterYSize,
                          buf_pixel_space=3, buf_band_space=1)
+    y = int(ds.RasterYSize/2)
+    data_bottom = ds.ReadRaster(0, y, ds.RasterXSize, ds.RasterYSize - y,
+                                buf_pixel_space=3, buf_band_space=1)
+    data_top = ds.ReadRaster(0, 0, ds.RasterXSize, y,
+                             buf_pixel_space=3, buf_band_space=1)
+    assert data == data_top + data_bottom
     tmp_ds = gdal.GetDriverByName('Mem').Create(
         '', ds.RasterXSize, ds.RasterYSize, 3)
     tmp_ds.WriteRaster(0, 0, ds.RasterXSize, ds.RasterYSize, data,
@@ -806,6 +813,7 @@ def test_jpeg_23():
     assert cs == got_cs
 
     # Pixel interleaved with padding
+    ds = gdal.Open('data/albania.jpg')
     data = ds.ReadRaster(0, 0, ds.RasterXSize, ds.RasterYSize,
                          buf_pixel_space=4, buf_band_space=1)
     tmp_ds = gdal.GetDriverByName('Mem').Create(
diff --git a/gdal/frmts/jpeg/jpgdataset.cpp b/gdal/frmts/jpeg/jpgdataset.cpp
index 6ecc2b4e6512..422794f5648f 100644
--- a/gdal/frmts/jpeg/jpgdataset.cpp
+++ b/gdal/frmts/jpeg/jpgdataset.cpp
@@ -1869,7 +1869,7 @@ CPLErr JPGDatasetCommon::IRasterIO( GDALRWFlag eRWFlag,
                     }
                 }
             }
-            nLoadedScanline = -1;
+            nLoadedScanline = nRasterYSize;
         }
         else
         {