fix mapim typo

oops! typo ... also an off-by-one issue for larger stencils

more error checking in interpolators

fix rounding in nohalo/lbb ... they were rounding to nearest in the
interpolator, rather than using floor. This broke assumptions about
stencil position elsewhere. The right way to do centre convention is to offset
the whole input by 0.5 pixels.

TODO

@@ -1,11 +1,5 @@
-
-- easy to get a segv with Nicolas's interpolators, argh
-
-  just with float images?
-
-  try to_polar workspace, set LBB, zoom in and scroll around a bit
-
-
+- get some brightly coloured spots with nohalo / vsqbs on wobble.ws ... very
+  odd, the interpolation shouldn't change between bands
 
 - still not happy about float->int mask conversion in im_vips2mask.c
 

libvips/resample/bicubic.cpp

@@ -408,6 +408,17 @@ vips_interpolate_bicubic_interpolate( VipsInterpolate *interpolate,
 	const int bands = in->im->Bands;
 	const int lskip = VIPS_REGION_LSKIP( in );
 
+	g_assert( ix - 1 >= in->valid.left );
+	g_assert( iy - 1 >= in->valid.top );
+	g_assert( ix + 2 < VIPS_RECT_RIGHT( &in->valid ) );
+	g_assert( iy + 2 < VIPS_RECT_BOTTOM( &in->valid ) );
+
+	/* Confirm that absolute_x and absolute_y are >= 1, because of
+	 * window_offset.
+	 */
+	g_assert( x >= 1.0 );
+	g_assert( y >= 1.0 );
+
 #ifdef DEBUG
 	printf( "vips_interpolate_bicubic_interpolate: %g %g\n", x, y );
 	printf( "\tleft=%d, top=%d, width=%d, height=%d\n",

libvips/resample/interpolate.c

@@ -513,6 +513,11 @@ vips_interpolate_bilinear_interpolate( VipsInterpolate *interpolate,
 
 	int z;
 
+	g_assert( (int) x >= in->valid.left );
+	g_assert( (int) y >= in->valid.top );
+	g_assert( (int) x + 1 < VIPS_RECT_RIGHT( &in->valid ) );
+	g_assert( (int) y + 1 < VIPS_RECT_BOTTOM( &in->valid ) );
+
 	SWITCH_INTERPOLATE( in->im->BandFmt,
 		BILINEAR_INT, BILINEAR_FLOAT );
 }

libvips/resample/lbb.cpp

@@ -800,6 +800,11 @@ vips_interpolate_lbb_interpolate( VipsInterpolate* restrict interpolate,
     vips_band_format_iscomplex( in->im->BandFmt ) ? 
       2 * actual_bands : actual_bands;
 
+  g_assert( ix - 1 >= in->valid.left );
+  g_assert( iy - 1 >= in->valid.top );
+  g_assert( ix + 2 < VIPS_RECT_RIGHT( &in->valid ) );
+  g_assert( iy + 2 < VIPS_RECT_BOTTOM( &in->valid ) );
+
   /* Confirm that absolute_x and absolute_y are >= 1, see above. 
    */
   g_assert( absolute_x >= 1.0 );

libvips/resample/mapim.c

@@ -188,7 +188,7 @@ vips_mapim_region_minmax( VipsRegion *region, VipsRect *r, VipsRect *bounds )
 			for( z = 0; z < ps; z++ )  \
 				q[z] = 0; \
 		} \
-		else  \
+		else \
 			interpolate( mapim->interpolate, q, ir[0], \
 				px + window_offset, py + window_offset ); \
 		\
@@ -243,8 +243,6 @@ vips_mapim_gen( VipsRegion *or, void *seq, void *a, void *b, gboolean *stop )
 	 */
 	bounds.width += window_size - 1;
 	bounds.height += window_size - 1;
-	bounds.left -= window_offset;
-	bounds.height -= window_offset;
 
 	/* Clip against the source image.
 	 */

libvips/resample/nohalo.cpp

@@ -1493,8 +1493,8 @@ vips_interpolate_nohalo_interpolate( VipsInterpolate* restrict interpolate,
    *
    * It's 2 not 0 since we ask for a window_offset of 2 at the bottom.
    */
-  const int ix = (int) (absolute_x + 0.5);
-  const int iy = (int) (absolute_y + 0.5);
+  const int ix = (int) absolute_x;
+  const int iy = (int) absolute_y;
 
   /*
    * Move the pointer to (the first band of) the top/left pixel of the
@@ -1521,6 +1521,11 @@ vips_interpolate_nohalo_interpolate( VipsInterpolate* restrict interpolate,
     vips_band_format_iscomplex( in->im->BandFmt ) ? 
       2 * actual_bands : actual_bands;
 
+  g_assert( ix - 2 >= in->valid.left );
+  g_assert( iy - 2 >= in->valid.top );
+  g_assert( ix + 2 < VIPS_RECT_RIGHT( &in->valid ) );
+  g_assert( iy + 2 < VIPS_RECT_BOTTOM( &in->valid ) );
+
   /* Confirm that absolute_x and absolute_y are >= 2, see above. 
    */
   g_assert( absolute_x >= 2.0 );

libvips/resample/vsqbs.cpp

@@ -313,8 +313,8 @@ vips_interpolate_vsqbs_interpolate( VipsInterpolate* restrict interpolate,
    *
    * It's 1 not 0 since we ask for a window_offset of 1 at the bottom.
    */
-  const int ix = (int) (absolute_x + 0.5);
-  const int iy = (int) (absolute_y + 0.5);
+  const int ix = (int) absolute_x;
+  const int iy = (int) absolute_y;
 
   /*
    * Move the pointer to (the first band of) the top/left pixel of the
@@ -341,6 +341,11 @@ vips_interpolate_vsqbs_interpolate( VipsInterpolate* restrict interpolate,
     vips_band_format_iscomplex( in->im->BandFmt ) ? 
       2 * actual_bands : actual_bands;
 
+  g_assert( ix - 1 >= in->valid.left );
+  g_assert( iy - 1 >= in->valid.top );
+  g_assert( ix + 1 < VIPS_RECT_RIGHT( &in->valid ) );
+  g_assert( iy + 1 < VIPS_RECT_BOTTOM( &in->valid ) );
+
   /* Confirm that absolute_x and absolute_y are >= 1, see above. 
    */
   g_assert( absolute_x >= 1.0 );