From 569964d7e4de9c200c33423f15ad56fd74417066 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Mon, 25 Jan 2021 01:31:18 +0900
Subject: [PATCH] Cache SubImage for the empty images

---
 ebitenutil/shapes.go | 5 +++--
 image.go             | 7 +++++--
 vector/path.go       | 7 +++++--
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/ebitenutil/shapes.go b/ebitenutil/shapes.go
index 901ddca23..a0284dab3 100644
--- a/ebitenutil/shapes.go
+++ b/ebitenutil/shapes.go
@@ -24,7 +24,8 @@ import (
 )
 
 var (
-	emptyImage = ebiten.NewImage(3, 3)
+	emptyImage    = ebiten.NewImage(3, 3)
+	emptySubImage = emptyImage.SubImage(image.Rect(1, 1, 2, 2)).(*ebiten.Image)
 )
 
 func init() {
@@ -46,7 +47,7 @@ func DrawLine(dst *ebiten.Image, x1, y1, x2, y2 float64, clr color.Color) {
 	op.ColorM = colormcache.ColorToColorM(clr)
 	// Filter must be 'nearest' filter (default).
 	// Linear filtering would make edges blurred.
-	dst.DrawImage(emptyImage.SubImage(image.Rect(1, 1, 2, 2)).(*ebiten.Image), op)
+	dst.DrawImage(emptySubImage, op)
 }
 
 // DrawRect draws a rectangle on the given destination dst.
diff --git a/image.go b/image.go
index 6f342bd9e..4dbe077c4 100644
--- a/image.go
+++ b/image.go
@@ -69,7 +69,10 @@ func (i *Image) Clear() {
 	i.Fill(color.Transparent)
 }
 
-var emptyImage = NewImage(3, 3)
+var (
+	emptyImage    = NewImage(3, 3)
+	emptySubImage = emptyImage.SubImage(image.Rect(1, 1, 2, 2)).(*Image)
+)
 
 func init() {
 	w, h := emptyImage.Size()
@@ -101,7 +104,7 @@ func (i *Image) Fill(clr color.Color) {
 	op.ColorM.Scale(rf, gf, bf, af)
 	op.CompositeMode = CompositeModeCopy
 
-	i.DrawImage(emptyImage.SubImage(image.Rect(1, 1, 2, 2)).(*Image), op)
+	i.DrawImage(emptySubImage, op)
 }
 
 func canSkipMipmap(geom GeoM, filter driver.Filter) bool {
diff --git a/vector/path.go b/vector/path.go
index a00e64df4..ef8fe05fb 100644
--- a/vector/path.go
+++ b/vector/path.go
@@ -26,7 +26,10 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/vector/internal/triangulate"
 )
 
-var emptyImage = ebiten.NewImage(3, 3)
+var (
+	emptyImage    = ebiten.NewImage(3, 3)
+	emptySubImage = emptyImage.SubImage(image.Rect(1, 1, 2, 2)).(*ebiten.Image)
+)
 
 func init() {
 	emptyImage.Fill(color.White)
@@ -139,5 +142,5 @@ func (p *Path) Fill(dst *ebiten.Image, op *FillOptions) {
 		}
 		base += uint16(len(seg))
 	}
-	dst.DrawTriangles(vertices, indices, emptyImage.SubImage(image.Rect(1, 1, 2, 2)).(*ebiten.Image), nil)
+	dst.DrawTriangles(vertices, indices, emptySubImage, nil)
 }