ebiten: add ColorM.ScaleWithColor

Updates #1944

colorm.go

@@ -76,6 +76,16 @@ func (c *ColorM) Scale(r, g, b, a float64) {
 	c.impl = c.affineColorM().Scale(float32(r), float32(g), float32(b), float32(a))
 }
 
+// ScaleWithColor scales the matrix by clr.
+func (c *ColorM) ScaleWithColor(clr color.Color) {
+	cr, cg, cb, ca := clr.RGBA()
+	if ca == 0 {
+		c.Scale(0, 0, 0, 0)
+		return
+	}
+	c.Scale(float64(cr)/float64(ca), float64(cg)/float64(ca), float64(cb)/float64(ca), float64(ca)/0xffff)
+}
+
 // Translate translates the matrix by (r, g, b, a).
 func (c *ColorM) Translate(r, g, b, a float64) {
 	c.impl = c.affineColorM().Translate(float32(r), float32(g), float32(b), float32(a))

ebitenutil/shapes.go

@@ -31,14 +31,6 @@ func init() {
 	emptyImage.Fill(color.White)
 }
 
-func colorToScale(clr color.Color) (float64, float64, float64, float64) {
-	cr, cg, cb, ca := clr.RGBA()
-	if ca == 0 {
-		return 0, 0, 0, 0
-	}
-	return float64(cr) / float64(ca), float64(cg) / float64(ca), float64(cb) / float64(ca), float64(ca) / 0xffff
-}
-
 // DrawLine draws a line segment on the given destination dst.
 //
 // DrawLine is intended to be used mainly for debugging or prototyping purpose.
@@ -49,7 +41,7 @@ func DrawLine(dst *ebiten.Image, x1, y1, x2, y2 float64, clr color.Color) {
 	op.GeoM.Scale(length, 1)
 	op.GeoM.Rotate(math.Atan2(y2-y1, x2-x1))
 	op.GeoM.Translate(x1, y1)
-	op.ColorM.Scale(colorToScale(clr))
+	op.ColorM.ScaleWithColor(clr)
 	// Filter must be 'nearest' filter (default).
 	// Linear filtering would make edges blurred.
 	dst.DrawImage(emptySubImage, op)
@@ -62,7 +54,7 @@ func DrawRect(dst *ebiten.Image, x, y, width, height float64, clr color.Color) {
 	op := &ebiten.DrawImageOptions{}
 	op.GeoM.Scale(width, height)
 	op.GeoM.Translate(x, y)
-	op.ColorM.Scale(colorToScale(clr))
+	op.ColorM.ScaleWithColor(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)

examples/2048/2048/board.go

@@ -129,8 +129,7 @@ func (b *Board) Draw(boardImage *ebiten.Image) {
 			x := i*tileSize + (i+1)*tileMargin
 			y := j*tileSize + (j+1)*tileMargin
 			op.GeoM.Translate(float64(x), float64(y))
-			r, g, b, a := colorToScale(tileBackgroundColor(v))
-			op.ColorM.Scale(r, g, b, a)
+			op.ColorM.ScaleWithColor(tileBackgroundColor(v))
 			boardImage.DrawImage(tileImage, op)
 		}
 	}

examples/2048/2048/tile.go

@@ -322,21 +322,6 @@ func (t *Tile) Update() error {
 	return nil
 }
 
-func colorToScale(clr color.Color) (float64, float64, float64, float64) {
-	r, g, b, a := clr.RGBA()
-	rf := float64(r) / 0xffff
-	gf := float64(g) / 0xffff
-	bf := float64(b) / 0xffff
-	af := float64(a) / 0xffff
-	// Convert to non-premultiplied alpha components.
-	if 0 < af {
-		rf /= af
-		gf /= af
-		bf /= af
-	}
-	return rf, gf, bf, af
-}
-
 func mean(a, b int, rate float64) int {
 	return int(float64(a)*(1-rate) + float64(b)*rate)
 }
@@ -398,8 +383,7 @@ func (t *Tile) Draw(boardImage *ebiten.Image) {
 		op.GeoM.Translate(float64(tileSize/2), float64(tileSize/2))
 	}
 	op.GeoM.Translate(float64(x), float64(y))
-	r, g, b, a := colorToScale(tileBackgroundColor(v))
-	op.ColorM.Scale(r, g, b, a)
+	op.ColorM.ScaleWithColor(tileBackgroundColor(v))
 	boardImage.DrawImage(tileImage, op)
 	str := strconv.Itoa(v)
 

image.go

@@ -100,16 +100,7 @@ func (i *Image) Fill(clr color.Color) {
 
 	op := &DrawImageOptions{}
 	op.GeoM.Scale(float64(w), float64(h))
-
-	r, g, b, a := clr.RGBA()
-	var rf, gf, bf, af float64
-	if a > 0 {
-		rf = float64(r) / float64(a)
-		gf = float64(g) / float64(a)
-		bf = float64(b) / float64(a)
-		af = float64(a) / 0xffff
-	}
-	op.ColorM.Scale(rf, gf, bf, af)
+	op.ColorM.ScaleWithColor(clr)
 	op.CompositeMode = CompositeModeCopy
 
 	i.DrawImage(emptySubImage, op)

text/text.go

@@ -179,14 +179,9 @@ var textM sync.Mutex
 //
 // Draw is concurrent-safe.
 func Draw(dst *ebiten.Image, text string, face font.Face, x, y int, clr color.Color) {
-	cr, cg, cb, ca := clr.RGBA()
-	if ca == 0 {
-		return
-	}
-
 	op := &ebiten.DrawImageOptions{}
 	op.GeoM.Translate(float64(x), float64(y))
-	op.ColorM.Scale(float64(cr)/float64(ca), float64(cg)/float64(ca), float64(cb)/float64(ca), float64(ca)/0xffff)
+	op.ColorM.ScaleWithColor(clr)
 	DrawWithOptions(dst, text, face, op)
 }