From 235eb87aa5d20c2badc4af15559a9f6031db6076 Mon Sep 17 00:00:00 2001
From: John Cupitt <jcupitt@gmail.com>
Date: Tue, 15 Jul 2014 09:05:00 +0100
Subject: [PATCH] sort out sense of fourier filter masks

---
 TODO                              | 70 +++++++++++++++++++++++++++++++
 libvips/create/mask_gaussian.c    |  2 +-
 libvips/create/mask_ideal.c       |  2 +-
 libvips/create/mask_ideal_band.c  |  2 +-
 libvips/deprecated/im_freq_mask.c |  6 +--
 5 files changed, 76 insertions(+), 6 deletions(-)

diff --git a/TODO b/TODO
index deae2057..35baacb2 100644
--- a/TODO
+++ b/TODO
@@ -1,3 +1,73 @@
+- butterworth highpass is wrong! actually makes a lowpass filter
+
+  $ ~/vips-7.26/bin/vips-7.26 vips im_create_fmask x2.v 32 32 2 42 0.5 0.5 0 0
+
+  is correct: a black circle on a white bg, with a white dot top left
+
+  2 because we have
+
+  	vips7compat.h:        IM_MASK_BUTTERWORTH_HIGHPASS = 2,
+
+  in vip8 this is
+
+  $ vips mask_butterworth x.v 32 32 42 0.5 0.5
+
+  generates a highpass filter, or 
+
+  $ vips mask_butterworth x.v 32 32 42 0.5 0.5 --reject
+
+  for a lowpass filter
+
+  doesn't match ideal! there we have --reject to make a highpass filter
+
+
+im_freq_mask has:
+
+	IM_MASK_IDEAL_HIGHPASS: 	0
+		if( vips_mask_ideal( 
+	IM_MASK_IDEAL_LOWPASS:		1
+		if( vips_mask_ideal( "reject", TRUE,  
+	IM_MASK_BUTTERWORTH_HIGHPASS:	2
+		if( vips_mask_butterworth( 
+	IM_MASK_BUTTERWORTH_LOWPASS:	3
+		if( vips_mask_butterworth( "reject", TRUE, 
+	IM_MASK_GAUSS_HIGHPASS:		4
+		if( vips_mask_gaussian(
+	IM_MASK_GAUSS_LOWPASS:		5
+		if( vips_mask_gaussian( "reject", TRUE,
+
+	IM_MASK_IDEAL_RINGPASS:		6
+		if( vips_mask_ideal_ring( 
+	IM_MASK_IDEAL_RINGREJECT:	7
+		if( vips_mask_ideal_ring(  "reject", TRUE,
+	IM_MASK_BUTTERWORTH_RINGPASS:	8
+		if( vips_mask_butterworth_ring( 
+	IM_MASK_BUTTERWORTH_RINGREJECT:	9
+		if( vips_mask_butterworth_ring(  "reject", TRUE,
+	IM_MASK_GAUSS_RINGPASS:		10
+		if( vips_mask_gaussian_ring(  
+	IM_MASK_GAUSS_RINGREJECT:	11
+		if( vips_mask_gaussian_ring(  "reject", TRUE,
+
+	IM_MASK_IDEAL_BANDPASS:		12
+		if( vips_mask_ideal_ring( 
+	IM_MASK_IDEAL_BANDREJECT:	13
+		if( vips_mask_ideal_ring(  "reject", TRUE,
+	IM_MASK_BUTTERWORTH_BANDPASS:	14
+		if( vips_mask_butterworth_ring( 
+	IM_MASK_BUTTERWORTH_BANDREJECT:	15
+		if( vips_mask_butterworth_ring(  "reject", TRUE,
+	IM_MASK_GAUSS_BANDPASS:		16
+		if( vips_mask_gaussian_ring(  
+	IM_MASK_GAUSS_BANDREJECT:	17
+		if( vips_mask_gaussian_ring(  "reject", TRUE,
+
+	IM_MASK_FRACTAL_FLT:		18
+		// not implemented
+
+
+
+
 
 - maxpos_avg seems to give variable results
 
diff --git a/libvips/create/mask_gaussian.c b/libvips/create/mask_gaussian.c
index ecf268d8..d59f5fc8 100644
--- a/libvips/create/mask_gaussian.c
+++ b/libvips/create/mask_gaussian.c
@@ -64,7 +64,7 @@ vips_mask_gaussian_point( VipsMask *mask, double dx, double dy )
 	double fc2 = fc * fc;
 	double dist2 = (dx * dx + dy * dy) / fc2;
 
-	return( exp( cnst * dist2 ) ); 
+	return( 1.0 - exp( cnst * dist2 ) ); 
 }
 
 static void
diff --git a/libvips/create/mask_ideal.c b/libvips/create/mask_ideal.c
index 6336b657..54625e75 100644
--- a/libvips/create/mask_ideal.c
+++ b/libvips/create/mask_ideal.c
@@ -62,7 +62,7 @@ vips_mask_ideal_point( VipsMask *mask, double dx, double dy )
 	double dist2 = dx * dx + dy * dy;
 	double fc2 = fc * fc;
 
-	return( dist2 <= fc2 ? 1.0 : 0.0 ); 
+	return( dist2 <= fc2 ? 0.0 : 1.0 ); 
 }
 
 static void
diff --git a/libvips/create/mask_ideal_band.c b/libvips/create/mask_ideal_band.c
index 17a2c80d..0718c2a5 100644
--- a/libvips/create/mask_ideal_band.c
+++ b/libvips/create/mask_ideal_band.c
@@ -76,7 +76,7 @@ vips_mask_ideal_band_point( VipsMask *mask, double dx, double dy )
 	double d1 = (dx - fcx) * (dx - fcx) + (dy - fcy) * (dy - fcy);
 	double d2 = (dx + fcx) * (dx + fcx) + (dy + fcy) * (dy + fcy);
 
-	return( d1 < r2 || d2 < r2 ? 1.0 : 0.0 ); 
+	return( (d1 < r2 || d2 < r2) ? 1.0 : 0.0 ); 
 }
 
 static void
diff --git a/libvips/deprecated/im_freq_mask.c b/libvips/deprecated/im_freq_mask.c
index a1218b81..129eefff 100644
--- a/libvips/deprecated/im_freq_mask.c
+++ b/libvips/deprecated/im_freq_mask.c
@@ -67,39 +67,39 @@ build_freq_mask( IMAGE *out, int xs, int ys, ImMaskType flag, va_list ap )
 	switch( flag ) {
 	case IM_MASK_IDEAL_HIGHPASS:
 		if( vips_mask_ideal( &t, xs, ys, p0,
-			"reject", TRUE, 
 			NULL ) )
 			return( -1 );
 		break;
 
 	case IM_MASK_IDEAL_LOWPASS:
 		if( vips_mask_ideal( &t, xs, ys, p0,
+			"reject", TRUE, 
 			NULL ) )
 			return( -1 );
 		break;
 
 	case IM_MASK_BUTTERWORTH_HIGHPASS:
 		if( vips_mask_butterworth( &t, xs, ys, p0, p1, p2,
-			"reject", TRUE, 
 			NULL ) )
 			return( -1 );
 		break;
 
 	case IM_MASK_BUTTERWORTH_LOWPASS:
 		if( vips_mask_butterworth( &t, xs, ys, p0, p1, p2,
+			"reject", TRUE, 
 			NULL ) )
 			return( -1 );
 		break;
 
 	case IM_MASK_GAUSS_HIGHPASS:
 		if( vips_mask_gaussian( &t, xs, ys, p0, p1, 
-			"reject", TRUE, 
 			NULL ) )
 			return( -1 );
 		break;
 
 	case IM_MASK_GAUSS_LOWPASS:
 		if( vips_mask_gaussian( &t, xs, ys, p0, p1, 
+			"reject", TRUE, 
 			NULL ) )
 			return( -1 );
 		break;