ebitenutil: Cache ColorM and reuse them at DrawRect

Fixes #1221

ebitenutil/shapes.go

@@ -19,6 +19,7 @@ import (
 	"math"
 
 	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/internal/colormcache"
 )
 
 var (
@@ -30,22 +31,11 @@ func init() {
 	_ = emptyImage.Fill(color.White)
 }
 
-func colorScale(clr color.Color) (rf, gf, bf, af float64) {
-	r, g, b, a := clr.RGBA()
-	if a == 0 {
-		return 0, 0, 0, 0
-	}
-
-	rf = float64(r) / float64(a)
-	gf = float64(g) / float64(a)
-	bf = float64(b) / float64(a)
-	af = float64(a) / 0xffff
-	return
-}
-
 // DrawLine draws a line segment on the given destination dst.
 //
 // DrawLine is intended to be used mainly for debugging or prototyping purpose.
+//
+// DrawLine is not concurrent-safe.
 func DrawLine(dst *ebiten.Image, x1, y1, x2, y2 float64, clr color.Color) {
 	ew, eh := emptyImage.Size()
 	length := math.Hypot(x2-x1, y2-y1)
@@ -54,7 +44,7 @@ func DrawLine(dst *ebiten.Image, x1, y1, x2, y2 float64, clr color.Color) {
 	op.GeoM.Scale(length/float64(ew), 1/float64(eh))
 	op.GeoM.Rotate(math.Atan2(y2-y1, x2-x1))
 	op.GeoM.Translate(x1, y1)
-	op.ColorM.Scale(colorScale(clr))
+	op.ColorM = colormcache.ColorToColorM(clr)
 	// Filter must be 'nearest' filter (default).
 	// Linear filtering would make edges blurred.
 	_ = dst.DrawImage(emptyImage, op)
@@ -63,13 +53,15 @@ func DrawLine(dst *ebiten.Image, x1, y1, x2, y2 float64, clr color.Color) {
 // DrawRect draws a rectangle on the given destination dst.
 //
 // DrawRect is intended to be used mainly for debugging or prototyping purpose.
+//
+// DrawRect is not concurrent-safe.
 func DrawRect(dst *ebiten.Image, x, y, width, height float64, clr color.Color) {
 	ew, eh := emptyImage.Size()
 
 	op := &ebiten.DrawImageOptions{}
 	op.GeoM.Scale(width/float64(ew), height/float64(eh))
 	op.GeoM.Translate(x, y)
-	op.ColorM.Scale(colorScale(clr))
+	op.ColorM = colormcache.ColorToColorM(clr)
 	// Filter must be 'nearest' filter (default).
 	// Linear filtering would make edges blurred.
 	_ = dst.DrawImage(emptyImage, op)

internal/colormcache/cache.go

@@ -0,0 +1,96 @@
+// Copyright 2020 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package colormcache
+
+import (
+	"image/color"
+	"math"
+
+	"github.com/hajimehoshi/ebiten"
+)
+
+var (
+	monotonicClock int64
+)
+
+func now() int64 {
+	monotonicClock++
+	return monotonicClock
+}
+
+const (
+	cacheLimit = 512 // This is an arbitrary number.
+)
+
+type colorMCacheKey uint32
+
+type colorMCacheEntry struct {
+	m     ebiten.ColorM
+	atime int64
+}
+
+var (
+	colorMCache = map[colorMCacheKey]*colorMCacheEntry{}
+	emptyColorM ebiten.ColorM
+)
+
+func init() {
+	emptyColorM.Scale(0, 0, 0, 0)
+}
+
+func ColorToColorM(clr color.Color) ebiten.ColorM {
+	// RGBA() is in [0 - 0xffff]. Adjust them in [0 - 0xff].
+	cr, cg, cb, ca := clr.RGBA()
+	cr /= 0x101
+	cg /= 0x101
+	cb /= 0x101
+	ca /= 0x101
+	if ca == 0 {
+		return emptyColorM
+	}
+
+	key := colorMCacheKey(uint32(cr) | (uint32(cg) << 8) | (uint32(cb) << 16) | (uint32(ca) << 24))
+	e, ok := colorMCache[key]
+	if ok {
+		e.atime = now()
+		return e.m
+	}
+
+	if len(colorMCache) > cacheLimit {
+		oldest := int64(math.MaxInt64)
+		oldestKey := colorMCacheKey(0)
+		for key, c := range colorMCache {
+			if c.atime < oldest {
+				oldestKey = key
+				oldest = c.atime
+			}
+		}
+		delete(colorMCache, oldestKey)
+	}
+
+	cm := ebiten.ColorM{}
+	rf := float64(cr) / float64(ca)
+	gf := float64(cg) / float64(ca)
+	bf := float64(cb) / float64(ca)
+	af := float64(ca) / 0xff
+	cm.Scale(rf, gf, bf, af)
+	e = &colorMCacheEntry{
+		m:     cm,
+		atime: now(),
+	}
+	colorMCache[key] = e
+
+	return e.m
+}

text/text.go

@@ -27,6 +27,7 @@ import (
 	"golang.org/x/image/math/fixed"
 
 	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/internal/colormcache"
 )
 
 var (
@@ -46,13 +47,6 @@ const (
 	cacheLimit = 512 // This is an arbitrary number.
 )
 
-type colorMCacheKey uint32
-
-type colorMCacheEntry struct {
-	m     ebiten.ColorM
-	atime int64
-}
-
 func drawGlyph(dst *ebiten.Image, face font.Face, r rune, img *glyphImage, x, y fixed.Int26_6, clr ebiten.ColorM) {
 	if img == nil {
 		return
@@ -202,58 +196,6 @@ func getGlyphImages(face font.Face, runes []rune) []*glyphImage {
 
 var textM sync.Mutex
 
-var (
-	colorMCache = map[colorMCacheKey]*colorMCacheEntry{}
-	emptyColorM ebiten.ColorM
-)
-
-func init() {
-	emptyColorM.Scale(0, 0, 0, 0)
-}
-
-func colorToColorM(clr color.Color) ebiten.ColorM {
-	// RGBA() is in [0 - 0xffff]. Adjust them in [0 - 0xff].
-	cr, cg, cb, ca := clr.RGBA()
-	cr >>= 8
-	cg >>= 8
-	cb >>= 8
-	ca >>= 8
-	if ca == 0 {
-		return emptyColorM
-	}
-	key := colorMCacheKey(uint32(cr) | (uint32(cg) << 8) | (uint32(cb) << 16) | (uint32(ca) << 24))
-	e, ok := colorMCache[key]
-	if ok {
-		e.atime = now()
-		return e.m
-	}
-	if len(colorMCache) > cacheLimit {
-		oldest := int64(math.MaxInt64)
-		oldestKey := colorMCacheKey(0)
-		for key, c := range colorMCache {
-			if c.atime < oldest {
-				oldestKey = key
-				oldest = c.atime
-			}
-		}
-		delete(colorMCache, oldestKey)
-	}
-
-	cm := ebiten.ColorM{}
-	rf := float64(cr) / float64(ca)
-	gf := float64(cg) / float64(ca)
-	bf := float64(cb) / float64(ca)
-	af := float64(ca) / 0xff
-	cm.Scale(rf, gf, bf, af)
-	e = &colorMCacheEntry{
-		m:     cm,
-		atime: now(),
-	}
-	colorMCache[key] = e
-
-	return e.m
-}
-
 // Draw draws a given text on a given destination image dst.
 //
 // face is the font for text rendering.
@@ -282,7 +224,7 @@ func Draw(dst *ebiten.Image, text string, face font.Face, x, y int, clr color.Co
 
 	runes := []rune(text)
 	glyphImgs := getGlyphImages(face, runes)
-	colorm := colorToColorM(clr)
+	colorm := colormcache.ColorToColorM(clr)
 
 	for i, r := range runes {
 		if prevR >= 0 {