From 4aeedd971131ee86005e236fe1b6cfdcbd128cd6 Mon Sep 17 00:00:00 2001
From: John Cupitt <jcupitt@gmail.com>
Date: Thu, 30 Jan 2020 16:53:18 +0000
Subject: [PATCH] add "nearest" region shrink

---
 libvips/include/vips/region.h   |  2 ++
 libvips/iofuncs/enumtypes.c     |  1 +
 libvips/iofuncs/region.c        | 25 +++++++++++++++++++------
 test/test-suite/test_foreign.py |  5 ++++-
 4 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/libvips/include/vips/region.h b/libvips/include/vips/region.h
index bcce3c47..d52a3fa7 100644
--- a/libvips/include/vips/region.h
+++ b/libvips/include/vips/region.h
@@ -62,6 +62,7 @@ extern "C" {
  * @VIPS_REGION_SHRINK_MODE: use the mode
  * @VIPS_REGION_SHRINK_MAX: use the maximum
  * @VIPS_REGION_SHRINK_MIN: use the minimum
+ * @VIPS_REGION_SHRINK_NEAREST: use the top-left pixel
  *
  * How to calculate the output pixels when shrinking a 2x2 region.
  */
@@ -71,6 +72,7 @@ typedef enum {
 	VIPS_REGION_SHRINK_MODE,
 	VIPS_REGION_SHRINK_MAX,
 	VIPS_REGION_SHRINK_MIN,
+	VIPS_REGION_SHRINK_NEAREST,
 	VIPS_REGION_SHRINK_LAST
 } VipsRegionShrink;
 
diff --git a/libvips/iofuncs/enumtypes.c b/libvips/iofuncs/enumtypes.c
index 2f571331..767a43f9 100644
--- a/libvips/iofuncs/enumtypes.c
+++ b/libvips/iofuncs/enumtypes.c
@@ -905,6 +905,7 @@ vips_region_shrink_get_type( void )
 			{VIPS_REGION_SHRINK_MODE, "VIPS_REGION_SHRINK_MODE", "mode"},
 			{VIPS_REGION_SHRINK_MAX, "VIPS_REGION_SHRINK_MAX", "max"},
 			{VIPS_REGION_SHRINK_MIN, "VIPS_REGION_SHRINK_MIN", "min"},
+			{VIPS_REGION_SHRINK_NEAREST, "VIPS_REGION_SHRINK_NEAREST", "nearest"},
 			{VIPS_REGION_SHRINK_LAST, "VIPS_REGION_SHRINK_LAST", "last"},
 			{0, NULL, NULL}
 		};
diff --git a/libvips/iofuncs/region.c b/libvips/iofuncs/region.c
index ab201ff5..a59a5d9a 100644
--- a/libvips/iofuncs/region.c
+++ b/libvips/iofuncs/region.c
@@ -1283,8 +1283,6 @@ vips_region_shrink_uncoded_mean( VipsRegion *from,
         		tq[z] = v[index]; \
 		} \
 		\
-		/* Move on two pels in input. \
-		 */ \
 		p += ps << 1; \
 		q += ps; \
 	} \
@@ -1303,8 +1301,6 @@ vips_region_shrink_uncoded_mean( VipsRegion *from,
 				); \
 		} \
 		\
-		/* Move on two pels in input. \
-		 */ \
 		p += ps << 1; \
 		q += ps; \
 	} \
@@ -1323,8 +1319,20 @@ vips_region_shrink_uncoded_mean( VipsRegion *from,
 				); \
 		} \
 		\
-		/* Move on two pels in input. \
-		 */ \
+		p += ps << 1; \
+		q += ps; \
+	} \
+}
+
+#define SHRINK_TYPE_NEAREST( TYPE ) { \
+	for( x = 0; x < target->width; x++ ) { \
+		TYPE *tp = (TYPE *) p; \
+		TYPE *tp1 = (TYPE *) (p + ls); \
+		TYPE *tq = (TYPE *) q; \
+		\
+		for( z = 0; z < nb; z++ ) \
+        		tq[z] = tp[z]; \
+		\
 		p += ps << 1; \
 		q += ps; \
 	} \
@@ -1377,6 +1385,7 @@ VIPS_REGION_SHRINK( MAX );
 VIPS_REGION_SHRINK( MIN );
 VIPS_REGION_SHRINK( MODE );
 VIPS_REGION_SHRINK( MEDIAN );
+VIPS_REGION_SHRINK( NEAREST );
 
 /* Generate area @target in @to using pixels in @from. Non-complex.
  */
@@ -1405,6 +1414,10 @@ vips_region_shrink_uncoded( VipsRegion *from,
 			vips_region_shrink_uncoded_MIN( from, to, target );
 			break;
 
+		case VIPS_REGION_SHRINK_NEAREST:
+			vips_region_shrink_uncoded_NEAREST( from, to, target );
+			break;
+
 		default:
 			g_assert_not_reached();
 	}
diff --git a/test/test-suite/test_foreign.py b/test/test-suite/test_foreign.py
index 4c18af71..517f3379 100644
--- a/test/test-suite/test_foreign.py
+++ b/test/test-suite/test_foreign.py
@@ -419,11 +419,14 @@ class TestForeign:
         assert a.height == b.height
         assert a.avg() == b.avg()
 
-        # region-shrink added in 8.7
         x = pyvips.Image.new_from_file(TIF_FILE)
         buf = x.tiffsave_buffer(tile=True, pyramid=True, region_shrink="mean")
         buf = x.tiffsave_buffer(tile=True, pyramid=True, region_shrink="mode")
         buf = x.tiffsave_buffer(tile=True, pyramid=True, region_shrink="median")
+        buf = x.tiffsave_buffer(tile=True, pyramid=True, region_shrink="max")
+        buf = x.tiffsave_buffer(tile=True, pyramid=True, region_shrink="min")
+        buf = x.tiffsave_buffer(tile=True, pyramid=True,
+                                region_shrink="nearest")
 
     @skip_if_no("magickload")
     def test_magickload(self):