image/draw: have Transform take a f64.Aff3 instead of a *f64.Aff3.

It's more args (in terms of bytes), but fewer allocations (Transformer
is an interface). Either way, it's not really that big of a deal, but
the value instead of the pointer seems conceptually more correct.

Change-Id: Ibea76da17cbda0d9633110fd56044b4e2c690e81
Reviewed-on: https://go-review.googlesource.com/12669
Reviewed-by: Rob Pike <r@golang.org>

draw/example_test.go

@@ -37,7 +37,7 @@ func ExampleDraw() {
 		draw.CatmullRom,
 	}
 	const cos60, sin60 = 0.5, 0.866025404
-	t := &f64.Aff3{
+	t := f64.Aff3{
 		+2 * cos60, -2 * sin60, 100,
 		+2 * sin60, +2 * cos60, 100,
 	}
@@ -67,7 +67,7 @@ func ExampleDraw() {
 	for i, op := range ops {
 		dr := image.Rect(120+10*i, 150+60*i, 170+10*i, 200+60*i)
 		draw.NearestNeighbor.Scale(dst, dr, red, red.Bounds(), op, nil)
-		t := &f64.Aff3{
+		t := f64.Aff3{
 			+cos60, -sin60, float64(190 + 10*i),
 			+sin60, +cos60, float64(140 + 50*i),
 		}

draw/gen.go

@@ -913,13 +913,13 @@ const (
 			}
 		}
 
-		func (z $receiver) Transform(dst Image, s2d *f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
+		func (z $receiver) Transform(dst Image, s2d f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
 			var o Options
 			if opts != nil {
 				o = *opts
 			}
 
-			dr := transformRect(s2d, &sr)
+			dr := transformRect(&s2d, &sr)
 			// adr is the affected destination pixels.
 			adr := dst.Bounds().Intersect(dr)
 			adr, o.DstMask = clipAffectedDestRect(adr, o.DstMask, o.DstMaskP)
@@ -930,7 +930,7 @@ const (
 				op = Src
 			}
 
-			d2s := invert(s2d)
+			d2s := invert(&s2d)
 			// bias is a translation of the mapping from dst coordinates to src
 			// coordinates such that the latter temporarily have non-negative X
 			// and Y coordinates. This allows us to write int(f) instead of
@@ -1179,13 +1179,13 @@ const (
 			}
 		}
 
-		func (q *Kernel) Transform(dst Image, s2d *f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
+		func (q *Kernel) Transform(dst Image, s2d f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
 			var o Options
 			if opts != nil {
 				o = *opts
 			}
 
-			dr := transformRect(s2d, &sr)
+			dr := transformRect(&s2d, &sr)
 			// adr is the affected destination pixels.
 			adr := dst.Bounds().Intersect(dr)
 			adr, o.DstMask = clipAffectedDestRect(adr, o.DstMask, o.DstMaskP)
@@ -1195,7 +1195,7 @@ const (
 			if op == Over && o.SrcMask == nil && opaque(src) {
 				op = Src
 			}
-			d2s := invert(s2d)
+			d2s := invert(&s2d)
 			// bias is a translation of the mapping from dst coordinates to src
 			// coordinates such that the latter temporarily have non-negative X
 			// and Y coordinates. This allows us to write int(f) instead of

draw/impl.go

@@ -97,13 +97,13 @@ func (z nnInterpolator) Scale(dst Image, dr image.Rectangle, src image.Image, sr
 	}
 }
 
-func (z nnInterpolator) Transform(dst Image, s2d *f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
+func (z nnInterpolator) Transform(dst Image, s2d f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
 	var o Options
 	if opts != nil {
 		o = *opts
 	}
 
-	dr := transformRect(s2d, &sr)
+	dr := transformRect(&s2d, &sr)
 	// adr is the affected destination pixels.
 	adr := dst.Bounds().Intersect(dr)
 	adr, o.DstMask = clipAffectedDestRect(adr, o.DstMask, o.DstMaskP)
@@ -114,7 +114,7 @@ func (z nnInterpolator) Transform(dst Image, s2d *f64.Aff3, src image.Image, sr
 		op = Src
 	}
 
-	d2s := invert(s2d)
+	d2s := invert(&s2d)
 	// bias is a translation of the mapping from dst coordinates to src
 	// coordinates such that the latter temporarily have non-negative X
 	// and Y coordinates. This allows us to write int(f) instead of
@@ -1118,13 +1118,13 @@ func (z ablInterpolator) Scale(dst Image, dr image.Rectangle, src image.Image, s
 	}
 }
 
-func (z ablInterpolator) Transform(dst Image, s2d *f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
+func (z ablInterpolator) Transform(dst Image, s2d f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
 	var o Options
 	if opts != nil {
 		o = *opts
 	}
 
-	dr := transformRect(s2d, &sr)
+	dr := transformRect(&s2d, &sr)
 	// adr is the affected destination pixels.
 	adr := dst.Bounds().Intersect(dr)
 	adr, o.DstMask = clipAffectedDestRect(adr, o.DstMask, o.DstMaskP)
@@ -1135,7 +1135,7 @@ func (z ablInterpolator) Transform(dst Image, s2d *f64.Aff3, src image.Image, sr
 		op = Src
 	}
 
-	d2s := invert(s2d)
+	d2s := invert(&s2d)
 	// bias is a translation of the mapping from dst coordinates to src
 	// coordinates such that the latter temporarily have non-negative X
 	// and Y coordinates. This allows us to write int(f) instead of
@@ -4498,13 +4498,13 @@ func (z *kernelScaler) Scale(dst Image, dr image.Rectangle, src image.Image, sr
 	}
 }
 
-func (q *Kernel) Transform(dst Image, s2d *f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
+func (q *Kernel) Transform(dst Image, s2d f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options) {
 	var o Options
 	if opts != nil {
 		o = *opts
 	}
 
-	dr := transformRect(s2d, &sr)
+	dr := transformRect(&s2d, &sr)
 	// adr is the affected destination pixels.
 	adr := dst.Bounds().Intersect(dr)
 	adr, o.DstMask = clipAffectedDestRect(adr, o.DstMask, o.DstMaskP)
@@ -4514,7 +4514,7 @@ func (q *Kernel) Transform(dst Image, s2d *f64.Aff3, src image.Image, sr image.R
 	if op == Over && o.SrcMask == nil && opaque(src) {
 		op = Src
 	}
-	d2s := invert(s2d)
+	d2s := invert(&s2d)
 	// bias is a translation of the mapping from dst coordinates to src
 	// coordinates such that the latter temporarily have non-negative X
 	// and Y coordinates. This allows us to write int(f) instead of

draw/scale.go

@@ -54,7 +54,7 @@ type Scaler interface {
 //
 // A Transformer is safe to use concurrently.
 type Transformer interface {
-	Transform(dst Image, m *f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options)
+	Transform(dst Image, m f64.Aff3, src image.Image, sr image.Rectangle, op Op, opts *Options)
 }
 
 // Options are optional parameters to Copy, Scale and Transform.

draw/scale_test.go

@@ -23,9 +23,9 @@ import (
 
 var genGoldenFiles = flag.Bool("gen_golden_files", false, "whether to generate the TestXxx golden files.")
 
-var transformMatrix = func(scale, tx, ty float64) *f64.Aff3 {
+var transformMatrix = func(scale, tx, ty float64) f64.Aff3 {
 	const cos30, sin30 = 0.866025404, 0.5
-	return &f64.Aff3{
+	return f64.Aff3{
 		+scale * cos30, -scale * sin30, tx,
 		+scale * sin30, +scale * cos30, ty,
 	}
@@ -297,11 +297,11 @@ func TestSrcTranslationInvariance(t *testing.T) {
 				tsrc := &translatedImage{src, delta}
 				got := image.NewRGBA(image.Rect(0, 0, 20, 20))
 				if transform {
-					m := matMul(m00, &f64.Aff3{
+					m := matMul(&m00, &f64.Aff3{
 						1, 0, -float64(delta.X),
 						0, 1, -float64(delta.Y),
 					})
-					q.Transform(got, &m, tsrc, sr.Add(delta), Over, nil)
+					q.Transform(got, m, tsrc, sr.Add(delta), Over, nil)
 				} else {
 					q.Scale(got, got.Bounds(), tsrc, sr.Add(delta), Over, nil)
 				}