hit a snag

TODO

@@ -1,6 +1,20 @@
-- tests for convasep ... just check it matches convsep +/- some small amount
+- try edge.mat:
 
-- tests for conva
+	3 3 1 0 
+	 1  1  1 
+	-2 -2 -2 
+	 1  1  1 
+
+  then 
+
+	$ vips conva k2.jpg x.v edge.mat 
+	Floating point exception (core dumped)
+
+  because area == 0, so we get /0
+
+  probably a problem for convasep too
+
+- tests for convasep ... just check it matches convsep +/- some small amount
 
 - try this blur.mat
 

libvips/convolution/conva.c

@@ -79,9 +79,9 @@ $ vips im_max abs.v
  */
 
 /*
+ */
 #define DEBUG
 #define VIPS_DEBUG
- */
 
 #ifdef HAVE_CONFIG_H
 #include <config.h>
@@ -909,17 +909,17 @@ vips_conva_hgenerate( VipsRegion *or, void *vseq,
 	for( y = 0; y < r->height; y++ ) { 
 		switch( in->BandFmt ) {
 		case VIPS_FORMAT_UCHAR: 	
-			if( conva->max_line > 256 )
+			if( conva->max_line < 256 )
-				HCONV( unsigned char, unsigned int );
-			else
 				HCONV( unsigned char, unsigned short );
+			else
+				HCONV( unsigned char, unsigned int );
 			break;
 
 		case VIPS_FORMAT_CHAR: 	
-			if( conva->max_line > 256 )
+			if( conva->max_line < 256 )
-				HCONV( signed char, signed int );
-			else
 				HCONV( signed char, signed short );
+			else
+				HCONV( signed char, signed int );
 			break;
 
 		case VIPS_FORMAT_USHORT: 	
@@ -1132,21 +1132,21 @@ vips_conva_vgenerate( VipsRegion *or, void *vseq,
 
 	switch( convolution->in->BandFmt ) {
 	case VIPS_FORMAT_UCHAR: 	
-		if( conva->max_line > 256 )
+		if( conva->max_line < 256 )
-			VCONV( unsigned int, \
-				unsigned int, unsigned char, CLIP_UCHAR );
-		else
 			VCONV( unsigned int, \
 				unsigned short, unsigned char, CLIP_UCHAR );
+		else
+			VCONV( unsigned int, \
+				unsigned int, unsigned char, CLIP_UCHAR );
 		break;
 
 	case VIPS_FORMAT_CHAR: 	
-		if( conva->max_line > 256 )
+		if( conva->max_line < 256 )
-			VCONV( signed int, \
-				signed int, signed char, CLIP_CHAR );
-		else
 			VCONV( signed int, \
 				signed short, signed char, CLIP_CHAR );
+		else
+			VCONV( signed int, \
+				signed int, signed char, CLIP_CHAR );
 		break;
 
 	case VIPS_FORMAT_USHORT: 	

test/test_convolution.py

@@ -96,6 +96,12 @@ class TestConvolution(unittest.TestCase):
         for x, y in zip_expand(a, b):
             self.assertAlmostEqual(x, y, places = places, msg = msg)
 
+    # test a pair of things which can be lists for difference less than a
+    # threshold
+    def assertLessThreshold(self, a, b, diff):
+        for x, y in zip_expand(a, b):
+            self.assertLess(abs(x - y), diff)
+
     def setUp(self):
         im = Vips.Image.mask_ideal(100, 100, 0.5, reject = True, optical = True)
         self.colour = im * [1, 2, 3] + [2, 3, 4]
@@ -125,12 +131,32 @@ class TestConvolution(unittest.TestCase):
 
                     result = convolved(25, 50)
                     true = conv(im, msk, 24, 49)
+                    print('result = %g, true = %g\n' % (result, true))
                     self.assertAlmostEqualObjects(result, true)
 
                     result = convolved(50, 50)
                     true = conv(im, msk, 49, 49)
                     self.assertAlmostEqualObjects(result, true)
 
+    def test_conva(self):
+        for im in self.all_images:
+            for msk in self.all_masks:
+                print("msk:")
+                msk.matrixprint()
+                print("im.bands = %s" % im.bands)
+
+                convolved = im.conv(msk, precision = Vips.Precision.APPROXIMATE)
+
+                result = convolved(25, 50)
+                true = conv(im, msk, 24, 49)
+                print("result = %s, true = %s" % (result, true))
+                self.assertLessThreshold(result, true, 5)
+
+                result = convolved(50, 50)
+                true = conv(im, msk, 49, 49)
+                print("result = %s, true = %s" % (result, true))
+                self.assertLessThreshold(result, true, 5)
+
     def test_compass(self):
         for im in self.all_images:
             for msk in self.all_masks: