From 1a25c7a083eaf10bb8f7155d6c3d150b4b690be8 Mon Sep 17 00:00:00 2001
From: John Cupitt <jcupitt@gmail.com>
Date: Fri, 25 Mar 2016 10:42:21 +0000
Subject: [PATCH] better rounding in vipsthumbnail

---
 TODO                   |  7 ++++---
 test/test_thumbnail.sh | 34 +++++++++++++++++++++-------------
 tools/vipsthumbnail.c  |  9 ++++++---
 3 files changed, 31 insertions(+), 19 deletions(-)

diff --git a/TODO b/TODO
index e9875188..5cfb21f4 100644
--- a/TODO
+++ b/TODO
@@ -1,7 +1,8 @@
-- test_thumbnail.sh is failing ... 1000->999 makes a 998 image
+- check C++ API for new operations
 
-- move 16->8 conversion to a separate pass? with so many constants, can't we
-  get an error for some mask sizes?
+- check dosc for new ops, esp function list
+
+- try make dist, check po
 
 - try SEQ_UNBUFFERED on jpg source, get out of order error?
 
diff --git a/test/test_thumbnail.sh b/test/test_thumbnail.sh
index 0b2af7d8..5044d0a0 100755
--- a/test/test_thumbnail.sh
+++ b/test/test_thumbnail.sh
@@ -8,11 +8,13 @@
 
 . ./variables.sh
 
-# make a 1000x1000 mono test image
+# make a 1000x1000 mono test image ... add a bit so the image should not 
+# contain any zeros, helps to spot missing tiles and bad pixels
 echo building test image ...
 vips extract_band $image $tmp/t1.v 1
-vips replicate $tmp/t1.v $tmp/t2.v 2 2
-vips extract_area $tmp/t2.v $tmp/t1.v 10 10 1000 1000
+vips linear $tmp/t1.v $tmp/t2.v 1 20 --uchar
+vips replicate $tmp/t2.v $tmp/t1.v 2 2
+vips crop $tmp/t1.v $tmp/t2.v 10 10 1000 1000
 
 # is a difference beyond a threshold? return 0 (meaning all ok) or 1 (meaning
 # error, or outside threshold)
@@ -25,29 +27,35 @@ break_threshold() {
 size=1000
 while [ $size -gt 99 ]; do
 	printf "testing size to $size ... "
-	vipsthumbnail $tmp/t1.v -o $tmp/t2.v --size $size 
-	if [ $(vipsheader -f width $tmp/t2.v) -ne $size ]; then
-		echo $tmp/t2.v failed -- bad size
-		echo output width is $(vipsheader -f width $tmp/t2.v) 
+	vipsthumbnail $tmp/t2.v -o $tmp/t1.v --size $size 
+	if [ $(vipsheader -f width $tmp/t1.v) -ne $size ]; then
+		echo $tmp/t1.v failed -- bad size
+		echo output width is $(vipsheader -f width $tmp/t1.v) 
 		exit
 	fi
-	if [ $(vipsheader -f height $tmp/t2.v) -ne $size ]; then
-		echo $tmp/t2.v failed -- bad size
-		echo output height is $(vipsheader -f width $tmp/t2.v) 
+	if [ $(vipsheader -f height $tmp/t1.v) -ne $size ]; then
+		echo $tmp/t1.v failed -- bad size
+		echo output height is $(vipsheader -f width $tmp/t1.v) 
 		exit
 	fi
 
-	vips project $tmp/t2.v $tmp/cols.v $tmp/rows.v
+	vips project $tmp/t1.v $tmp/cols.v $tmp/rows.v
 
 	min=$(vips min $tmp/cols.v)
 	if break_threshold $min 0; then
-		echo $tmp/t2.v failed -- has a black column
+		echo $tmp/t1.v failed -- has a black column
 		exit
 	fi
 
 	min=$(vips min $tmp/rows.v)
 	if break_threshold $min 0; then
-		echo $tmp/t2.v failed -- has a black row
+		echo $tmp/t1.v failed -- has a black row
+		exit
+	fi
+
+	min=$(vips min $tmp/t1.v)
+	if break_threshold $min 0; then
+		echo $tmp/t1.v failed -- has black pixels
 		exit
 	fi
 
diff --git a/tools/vipsthumbnail.c b/tools/vipsthumbnail.c
index bd326e09..c4659ede 100644
--- a/tools/vipsthumbnail.c
+++ b/tools/vipsthumbnail.c
@@ -187,11 +187,14 @@ calculate_shrink( VipsImage *im )
 	/* Calculate the horizontal and vertical shrink we'd need to fit the
 	 * image to the bounding box, and pick the biggest. 
 	 *
-	 * In crop mode we aim to fill the bounding box, so we must use the
+	 * In crop mode, we aim to fill the bounding box, so we must use the
 	 * smaller axis.
+	 *
+	 * Add a small amount so when vips_resize() later rounds down, we
+	 * don't round below target.
 	 */
-	double horizontal = (double) width / thumbnail_width;
-	double vertical = (double) height / thumbnail_height;
+	double horizontal = (double) width / (thumbnail_width + 0.1);
+	double vertical = (double) height / (thumbnail_height + 0.1);
 
 	if( crop_image ) {
 		if( horizontal < vertical )