Merge pull request #6437 from rouault/bilinear_fix_src_bounds_checks

Bilinear resampling: fix bound checks to avoid extending source raster by 0.5 target pixel

mapresample.c

@@ -342,6 +342,13 @@ msBilinearRasterResampler( imageObj *psSrcImage, rasterBufferObj *src_rb,
         continue;
       }
 
+      /* If we are right off the source, skip this pixel */
+      nSrcX = (int) floor(x[nDstX]);
+      nSrcY = (int) floor(y[nDstX]);
+      if( nSrcX < 0 || (!bWrapAtLeftRight && nSrcX >= nSrcXSize)
+          || nSrcY  < 0 || nSrcY >= nSrcYSize )
+        continue;
+
       /*
       ** Offset to treat TL pixel corners as pixel location instead
       ** of the center.
@@ -358,11 +365,6 @@ msBilinearRasterResampler( imageObj *psSrcImage, rasterBufferObj *src_rb,
       dfRatioX2 = x[nDstX] - nSrcX;
       dfRatioY2 = y[nDstX] - nSrcY;
 
-      /* If we are right off the source, skip this pixel */
-      if( nSrcX2 < 0 || (!bWrapAtLeftRight && nSrcX >= nSrcXSize)
-          || nSrcY2 < 0 || nSrcY >= nSrcYSize )
-        continue;
-
       /* Trim in stuff one pixel off the edge */
       nSrcX = MS_MAX(nSrcX,0);
       nSrcY = MS_MAX(nSrcY,0);

msautotest/gdal/bilinear_left_right.map

@@ -0,0 +1,37 @@
+# Test assembling two rasters and bilinear resampling
+MAP
+
+    NAME TEST
+    PROJECTION
+        "init=epsg:4326"
+    END
+
+    EXTENT -3.515625 -35.15625 3.515625 35.15625 
+    SIZE 32 320
+    IMAGETYPE png
+
+    LAYER
+        NAME "east-bilinear"
+        TYPE RASTER
+        STATUS default
+
+        PROJECTION
+            "init=epsg:4326"
+        END
+        PROCESSING "RESAMPLE=BILINEAR"
+        DATA "data/east.tif"
+    END
+
+    LAYER
+        NAME "west-bilinear"
+        TYPE RASTER
+        STATUS default
+
+        PROJECTION
+            "init=epsg:4326"
+        END
+        PROCESSING "RESAMPLE=BILINEAR"
+        DATA "data/west.tif"
+    END
+
+END

msautotest/gdal/bilinear_src_transp.map

@@ -6,7 +6,7 @@ MAP
 NAME TEST
 STATUS ON
 SIZE 400 40
-EXTENT 0.5 0.5 39.5 1.5
+EXTENT 0.5 1.5 39.5 2.5
 IMAGECOLOR 0 0 0
 
 OUTPUTFORMAT