From 31a54299fb2f2aa0194e2ae92187969b1fe5446e Mon Sep 17 00:00:00 2001
From: James Schofield <james@shoeboxapp.com>
Date: Thu, 3 Nov 2016 17:44:53 -0400
Subject: [PATCH 1/2] Handle 16-bit PNGs

---
 resize.go | 17 ++++-------------
 vips.go   | 11 +++++++++++
 vips.h    |  3 +--
 3 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/resize.go b/resize.go
index 8b5b8df..a8e0aeb 100644
--- a/resize.go
+++ b/resize.go
@@ -112,11 +112,8 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 		return nil, err
 	}
 
-	// Flatten image on a background, if necessary
-	image, err = imageFlatten(image, imageType, o)
-	if err != nil {
-		return nil, err
-	}
+	// Only flatten PNG for now
+	flatten := imageType == PNG && o.Background != ColorBlack
 
 	saveOptions := vipsSaveOptions{
 		Quality:        o.Quality,
@@ -125,6 +122,8 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 		Interlace:      o.Interlace,
 		NoProfile:      o.NoProfile,
 		Interpretation: o.Interpretation,
+		Flatten:        flatten,
+		Background:     o.Background,
 	}
 
 	// Finally get the resultant buffer
@@ -325,14 +324,6 @@ func watermakImage(image *C.VipsImage, w Watermark) (*C.VipsImage, error) {
 	return image, nil
 }
 
-func imageFlatten(image *C.VipsImage, imageType ImageType, o Options) (*C.VipsImage, error) {
-	// Only PNG images are supported for now
-	if imageType != PNG || o.Background == ColorBlack {
-		return image, nil
-	}
-	return vipsFlattenBackground(image, o.Background)
-}
-
 func zoomImage(image *C.VipsImage, zoom int) (*C.VipsImage, error) {
 	if zoom == 0 {
 		return image, nil
diff --git a/vips.go b/vips.go
index cbf2304..644bcf6 100644
--- a/vips.go
+++ b/vips.go
@@ -55,6 +55,8 @@ type vipsSaveOptions struct {
 	Interlace      bool
 	NoProfile      bool
 	Interpretation Interpretation
+	Flatten        bool
+	Background     Color
 }
 
 type vipsWatermarkOptions struct {
@@ -341,6 +343,15 @@ func vipsPreSave(image *C.VipsImage, o *vipsSaveOptions) (*C.VipsImage, error) {
 		image = outImage
 	}
 
+	// Flatten image on a background, if necessary
+	if o.Flatten {
+		var err error
+		if outImage, err = vipsFlattenBackground(image, o.Background); err != nil {
+			return nil, err
+		}
+		image = outImage
+	}
+
 	return image, nil
 }
 
diff --git a/vips.h b/vips.h
index 371de43..3e4a1a4 100644
--- a/vips.h
+++ b/vips.h
@@ -287,8 +287,7 @@ vips_flatten_background_brigde(VipsImage *in, VipsImage **out, double r, double
 	VipsArrayDouble *vipsBackground = vips_array_double_new(background, 3);
 
 	return vips_flatten(in, out,
-		"background", vipsBackground,
-		"max_alpha", vips_is_16bit(in->Type) ? 65535.0 : 255.0,
+		"background", vipsBackground, "max_alpha", 255.0,
 		NULL
 	);
 }

From a1b9efdb97aebb716b2415742f7bfeb065da3a9c Mon Sep 17 00:00:00 2001
From: James Schofield <james@shoeboxapp.com>
Date: Thu, 10 Nov 2016 15:15:52 -0500
Subject: [PATCH 2/2] Cleaner fix

---
 resize.go | 17 +++++++++++++----
 vips.go   | 11 -----------
 vips.h    |  9 ++++++++-
 3 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/resize.go b/resize.go
index a8e0aeb..8b5b8df 100644
--- a/resize.go
+++ b/resize.go
@@ -112,8 +112,11 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 		return nil, err
 	}
 
-	// Only flatten PNG for now
-	flatten := imageType == PNG && o.Background != ColorBlack
+	// Flatten image on a background, if necessary
+	image, err = imageFlatten(image, imageType, o)
+	if err != nil {
+		return nil, err
+	}
 
 	saveOptions := vipsSaveOptions{
 		Quality:        o.Quality,
@@ -122,8 +125,6 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 		Interlace:      o.Interlace,
 		NoProfile:      o.NoProfile,
 		Interpretation: o.Interpretation,
-		Flatten:        flatten,
-		Background:     o.Background,
 	}
 
 	// Finally get the resultant buffer
@@ -324,6 +325,14 @@ func watermakImage(image *C.VipsImage, w Watermark) (*C.VipsImage, error) {
 	return image, nil
 }
 
+func imageFlatten(image *C.VipsImage, imageType ImageType, o Options) (*C.VipsImage, error) {
+	// Only PNG images are supported for now
+	if imageType != PNG || o.Background == ColorBlack {
+		return image, nil
+	}
+	return vipsFlattenBackground(image, o.Background)
+}
+
 func zoomImage(image *C.VipsImage, zoom int) (*C.VipsImage, error) {
 	if zoom == 0 {
 		return image, nil
diff --git a/vips.go b/vips.go
index 644bcf6..cbf2304 100644
--- a/vips.go
+++ b/vips.go
@@ -55,8 +55,6 @@ type vipsSaveOptions struct {
 	Interlace      bool
 	NoProfile      bool
 	Interpretation Interpretation
-	Flatten        bool
-	Background     Color
 }
 
 type vipsWatermarkOptions struct {
@@ -343,15 +341,6 @@ func vipsPreSave(image *C.VipsImage, o *vipsSaveOptions) (*C.VipsImage, error) {
 		image = outImage
 	}
 
-	// Flatten image on a background, if necessary
-	if o.Flatten {
-		var err error
-		if outImage, err = vipsFlattenBackground(image, o.Background); err != nil {
-			return nil, err
-		}
-		image = outImage
-	}
-
 	return image, nil
 }
 
diff --git a/vips.h b/vips.h
index 3e4a1a4..c3f7d9e 100644
--- a/vips.h
+++ b/vips.h
@@ -283,11 +283,18 @@ vips_is_16bit (VipsInterpretation interpretation) {
 
 int
 vips_flatten_background_brigde(VipsImage *in, VipsImage **out, double r, double g, double b) {
+	if (vips_is_16bit(in->Type)) {
+		r = 65535 * r / 255;
+		g = 65535 * g / 255;
+		b = 65535 * b / 255;
+	}
+
 	double background[3] = {r, g, b};
 	VipsArrayDouble *vipsBackground = vips_array_double_new(background, 3);
 
 	return vips_flatten(in, out,
-		"background", vipsBackground, "max_alpha", 255.0,
+		"background", vipsBackground,
+		"max_alpha", vips_is_16bit(in->Type) ? 65535.0 : 255.0,
 		NULL
 	);
 }