From 339155f63dafe7d8d8595a48dbba7c6c468957ac Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sun, 10 Feb 2019 14:08:59 +0900
Subject: [PATCH] shareable: Use CompositeModeSourceOver when possible at Fill

---
 internal/shareable/shareable.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/internal/shareable/shareable.go b/internal/shareable/shareable.go
index e86dc6f0c..1eb0c039c 100644
--- a/internal/shareable/shareable.go
+++ b/internal/shareable/shareable.go
@@ -296,7 +296,11 @@ func (i *Image) Fill(r, g, b, a uint8) {
 		rf, gf, bf, af)
 	is := graphics.QuadIndices()
 
-	i.DrawImage(emptyImage, vs, is, nil, graphics.CompositeModeCopy, graphics.FilterNearest, graphics.AddressClampToZero)
+	c := graphics.CompositeModeSourceOver
+	if a < 0xff {
+		c = graphics.CompositeModeCopy
+	}
+	i.DrawImage(emptyImage, vs, is, nil, c, graphics.FilterNearest, graphics.AddressClampToZero)
 }
 
 func (i *Image) ReplacePixels(p []byte) {