vips_conv*() default to float

we had INT as the default, but this will cause serious precision loss
with many masks ... instead, have float (always correct) as the default
and let people turn on int if they cn

ChangeLog

@@ -4,10 +4,11 @@
   constant image
 - add new_from_image() to Python as well
 - slight change to cpp new_from_image() to match py/C behaviour
+- vips_conv(), vips_compass(), vips_convsep() default to FLOAT precision
 
 23/4/17 started 8.5.5
 - doc polishing
-- more improvements for tuncated PNG files, thanks juyunsang 
+- more improvements for truncated PNG files, thanks juyunsang 
 
 23/4/17 started 8.5.4
 - don't depend on image width when setting n_lines, thanks kleisauke

TODO

@@ -1,3 +1,5 @@
+- vips_compass() needs docs
+
 - cpp bandjoin should use bandjoin_const() where possibel ... currently 
   uses new_from_image
 

libvips/conversion/smartcrop.c

@@ -193,8 +193,12 @@ vips_smartcrop_attention( VipsSmartcrop *smartcrop,
 	/* Sobel edge-detect on L.
 	 */
 	if( vips_extract_band( t[1], &t[2], 0, NULL ) ||
-		vips_conv( t[2], &t[3], t[21], NULL ) ||
+		vips_conv( t[2], &t[3], t[21], 
-		vips_conv( t[2], &t[4], t[22], NULL ) ||
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
+		vips_conv( t[2], &t[4], t[22], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
 		vips_abs( t[3], &t[5], NULL ) ||
 		vips_abs( t[4], &t[6], NULL ) ||
 		vips_add( t[5], t[6], &t[7], NULL ) )

libvips/convolution/compass.c

@@ -2,6 +2,9 @@
  *
  * 23/10/13	
  * 	- from vips_conv()
+ * 8/5/17
+ *      - default to float ... int will often lose precision and should not be
+ *        the default
  */
 
 /*
@@ -172,7 +175,7 @@ vips_compass_class_init( VipsCompassClass *class )
 		_( "Convolve with this precision" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT, 
 		G_STRUCT_OFFSET( VipsCompass, precision ), 
-		VIPS_TYPE_PRECISION, VIPS_PRECISION_INTEGER ); 
+		VIPS_TYPE_PRECISION, VIPS_PRECISION_FLOAT ); 
 
 	VIPS_ARG_INT( class, "layers", 204, 
 		_( "Layers" ), 
@@ -196,7 +199,7 @@ vips_compass_init( VipsCompass *compass )
 	compass->times = 2;
 	compass->angle = VIPS_ANGLE45_D90;
 	compass->combine = VIPS_COMBINE_MAX;
-	compass->precision = VIPS_PRECISION_INTEGER;
+	compass->precision = VIPS_PRECISION_FLOAT;
 	compass->layers = 5;
 	compass->cluster = 1;
 }

libvips/convolution/conv.c

@@ -2,6 +2,9 @@
  *
  * 12/8/13	
  * 	- from vips_hist_cum()
+ * 8/5/17
+ * 	- default to float ... int will often lose precision and should not be
+ * 	  the default
  */
 
 /*
@@ -137,7 +140,7 @@ vips_conv_class_init( VipsConvClass *class )
 		_( "Convolve with this precision" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT, 
 		G_STRUCT_OFFSET( VipsConv, precision ), 
-		VIPS_TYPE_PRECISION, VIPS_PRECISION_INTEGER ); 
+		VIPS_TYPE_PRECISION, VIPS_PRECISION_FLOAT ); 
 
 	VIPS_ARG_INT( class, "layers", 104, 
 		_( "Layers" ), 
@@ -158,7 +161,7 @@ vips_conv_class_init( VipsConvClass *class )
 static void
 vips_conv_init( VipsConv *conv )
 {
-	conv->precision = VIPS_PRECISION_INTEGER;
+	conv->precision = VIPS_PRECISION_FLOAT;
 	conv->layers = 5;
 	conv->cluster = 1;
 }
@@ -187,22 +190,23 @@ vips_conv_init( VipsConv *conv )
  *
  * where scale and offset are part of @mask. 
  *
+ * By default, @precision is 
+ * #VIPS_PRECISION_FLOAT. The output image 
+ * is always #VIPS_FORMAT_FLOAT unless @in is #VIPS_FORMAT_DOUBLE, in which case
+ * @out is also #VIPS_FORMAT_DOUBLE. 
+ *
  * If @precision is #VIPS_PRECISION_INTEGER, then 
  * elements of @mask are converted to
  * integers before convolution, using rint(),
  * and the output image 
  * always has the same #VipsBandFormat as the input image. 
  *
- * For #VIPS_FORMAT_UCHAR images, vips_conv() uses a fast vector path based on
+ * For #VIPS_FORMAT_UCHAR images and #VIPS_PRECISION_INTEGER @precision, 
+ * vips_conv() uses a fast vector path based on
  * fixed-point arithmetic. This can produce slightly different results. 
  * Disable the vector path with `--vips-novector` or `VIPS_NOVECTOR` or
  * vips_vector_set_enabled().
  *
- * If @precision is #VIPS_PRECISION_FLOAT then the convolution is performed
- * with floating-point arithmetic. The output image 
- * is always #VIPS_FORMAT_FLOAT unless @in is #VIPS_FORMAT_DOUBLE, in which case
- * @out is also #VIPS_FORMAT_DOUBLE. 
- *
  * If @precision is #VIPS_PRECISION_APPROXIMATE then, like
  * #VIPS_PRECISION_INTEGER, @mask is converted to int before convolution, and 
  * the output image 

libvips/convolution/convsep.c

@@ -2,6 +2,9 @@
  *
  * 23/10/13	
  * 	- from vips_convsep()
+ * 8/5/17
+ *      - default to float ... int will often lose precision and should not be
+ *        the default
  */
 
 /*
@@ -128,7 +131,7 @@ vips_convsep_class_init( VipsConvsepClass *class )
 		_( "Convolve with this precision" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT, 
 		G_STRUCT_OFFSET( VipsConvsep, precision ), 
-		VIPS_TYPE_PRECISION, VIPS_PRECISION_INTEGER ); 
+		VIPS_TYPE_PRECISION, VIPS_PRECISION_FLOAT ); 
 
 	VIPS_ARG_INT( class, "layers", 204, 
 		_( "Layers" ), 
@@ -149,7 +152,7 @@ vips_convsep_class_init( VipsConvsepClass *class )
 static void
 vips_convsep_init( VipsConvsep *convsep )
 {
-	convsep->precision = VIPS_PRECISION_INTEGER;
+	convsep->precision = VIPS_PRECISION_FLOAT;
 	convsep->layers = 5;
 	convsep->cluster = 1;
 }

libvips/convolution/sharpen.c

@@ -264,7 +264,9 @@ vips_sharpen_build( VipsObject *object )
 	 */
 	if( vips_extract_band( in, &args[0], 0, NULL ) ||
 		vips_extract_band( in, &t[3], 1, "n", in->Bands - 1, NULL ) ||
-		vips_convsep( args[0], &args[1], t[1], NULL ) )
+		vips_convsep( args[0], &args[1], t[1], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) )
 		return( -1 );
 
 	/* Set demand hints. FATSTRIP is good for us, as THINSTRIP will cause

libvips/deprecated/vips7compat.c

@@ -2283,6 +2283,7 @@ im_compass( VipsImage *in, VipsImage *out, INTMASK *mask )
 	if( vips_compass( in, &t2, t1, 
 		"times", 8, 
 		"angle", VIPS_ANGLE45_D45, 
+		"precision", VIPS_PRECISION_INTEGER,
 		NULL ) ) {
 		g_object_unref( t1 );
 		return( -1 );
@@ -2308,6 +2309,7 @@ im_lindetect( IMAGE *in, IMAGE *out, INTMASK *mask )
 	if( vips_compass( in, &t2, t1, 
 		"times", 4, 
 		"angle", VIPS_ANGLE45_D45, 
+		"precision", VIPS_PRECISION_INTEGER,
 		NULL ) ) {
 		g_object_unref( t1 );
 		return( -1 );
@@ -2334,6 +2336,7 @@ im_gradient( IMAGE *in, IMAGE *out, INTMASK *mask )
 		"times", 2, 
 		"angle", VIPS_ANGLE45_D90, 
 		"combine", VIPS_COMBINE_SUM, 
+		"precision", VIPS_PRECISION_INTEGER,
 		NULL ) ) {
 		g_object_unref( t1 );
 		return( -1 );
@@ -2364,6 +2367,7 @@ im_convsep( IMAGE *in, IMAGE *out, INTMASK *mask )
 		im_imask2vips( mask, t1 ) )
 		return( -1 );
 	if( vips_convsep( in, &t2, t1, 
+		"precision", VIPS_PRECISION_INTEGER,
 		NULL ) ) {
 		g_object_unref( t1 );
 		return( -1 );
@@ -2393,9 +2397,7 @@ im_convsep_f( IMAGE *in, IMAGE *out, DOUBLEMASK *mask )
 	if( !(t1 = vips_image_new()) ||
 		im_mask2vips( mask, t1 ) )
 		return( -1 );
-	if( vips_convsep( in, &t2, t1, 
+	if( vips_convsep( in, &t2, t1, NULL ) ) {
-		"precision", VIPS_PRECISION_FLOAT,
-		NULL ) ) {
 		g_object_unref( t1 );
 		return( -1 );
 	}
@@ -2561,12 +2563,18 @@ im_contrast_surface( IMAGE *in, IMAGE *out, int half_win_size, int spacing )
 		for( x = 0; x < size; x++ )
 			*VIPS_MATRIX( t[8], x, y ) = 1.0;
 
-	if( vips_conv( in, &t[2], t[0], NULL ) ||
+	if( vips_conv( in, &t[2], t[0], 
-		vips_conv( in, &t[3], t[1], NULL ) ||
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
+		vips_conv( in, &t[3], t[1], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
 		vips_abs( t[2], &t[4], NULL ) ||
 		vips_abs( t[3], &t[5], NULL ) ||
 		vips_add( t[4], t[5], &t[6], NULL ) ||
-		vips_conv( t[6], &t[7], t[8], NULL ) ||
+		vips_conv( t[6], &t[7], t[8], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
 		vips_subsample( t[7], &t[9], spacing, spacing, NULL ) ||
 		vips_image_write( t[9], out ) )
 		return( -1 ); 

libvips/histogram/hist_ismonotonic.c

@@ -90,7 +90,9 @@ vips_hist_ismonotonic_build( VipsObject *object )
 
 	/* We want >=128 everywhere, ie. no -ve transitions.
 	 */
-	if( vips_conv( ismonotonic->in, &t[1], t[0], NULL ) ||
+	if( vips_conv( ismonotonic->in, &t[1], t[0], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
 		vips_moreeq_const1( t[1], &t[2], 128, NULL ) ||
 		vips_min( t[2], &m, NULL ) )
 		return( -1 );

libvips/morphology/countlines.c

@@ -92,7 +92,9 @@ vips_countlines_build( VipsObject *object )
 	case VIPS_DIRECTION_HORIZONTAL:
 		if( !(t[0] = vips_image_new_matrixv( 1, 2, -1.0, 1.0 )) ||
 			vips_moreeq_const1( in, &t[1], 128, NULL ) ||
-			vips_conv( t[1], &t[2], t[0], NULL ) ||
+			vips_conv( t[1], &t[2], t[0], 
+				"precision", VIPS_PRECISION_INTEGER,
+				NULL ) ||
 			vips_project( t[2], &t[3], &t[4], NULL ) ||
 			vips_avg( t[3], &nolines, NULL ) )
 			return( -1 ); 
@@ -101,7 +103,9 @@ vips_countlines_build( VipsObject *object )
 	case VIPS_DIRECTION_VERTICAL:
 		if( !(t[0] = vips_image_new_matrixv( 2, 1, -1.0, 1.0 )) ||
 			vips_moreeq_const1( in, &t[1], 128, NULL ) ||
-			vips_conv( t[1], &t[2], t[0], NULL ) ||
+			vips_conv( t[1], &t[2], t[0], 
+				"precision", VIPS_PRECISION_INTEGER,
+				NULL ) ||
 			vips_project( t[2], &t[3], &t[4], NULL ) ||
 			vips_avg( t[4], &nolines, NULL ) )
 			return( -1 );