vector: add some accumulate tests.

Change-Id: I199e1637698572e36b4a3bb83d652baf0d76717f
Reviewed-on: https://go-review.googlesource.com/30110
Reviewed-by: David Crawshaw <crawshaw@golang.org>
diff --git a/vector/acc_test.go b/vector/acc_test.go
new file mode 100644
index 0000000..8ba932e
--- /dev/null
+++ b/vector/acc_test.go
@@ -0,0 +1,431 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package vector
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+)
+
+func TestFixedAccumulateOpOverShort(t *testing.T)    { testAcc(t, fxInShort, fxMaskShort, "over") }
+func TestFixedAccumulateOpSrcShort(t *testing.T)     { testAcc(t, fxInShort, fxMaskShort, "src") }
+func TestFixedAccumulateMaskShort(t *testing.T)      { testAcc(t, fxInShort, fxMaskShort, "mask") }
+func TestFloatingAccumulateOpOverShort(t *testing.T) { testAcc(t, flInShort, flMaskShort, "over") }
+func TestFloatingAccumulateOpSrcShort(t *testing.T)  { testAcc(t, flInShort, flMaskShort, "src") }
+func TestFloatingAccumulateMaskShort(t *testing.T)   { testAcc(t, flInShort, flMaskShort, "mask") }
+
+func TestFixedAccumulateOpOver16(t *testing.T)    { testAcc(t, fxIn16, fxMask16, "over") }
+func TestFixedAccumulateOpSrc16(t *testing.T)     { testAcc(t, fxIn16, fxMask16, "src") }
+func TestFixedAccumulateMask16(t *testing.T)      { testAcc(t, fxIn16, fxMask16, "mask") }
+func TestFloatingAccumulateOpOver16(t *testing.T) { testAcc(t, flIn16, flMask16, "over") }
+func TestFloatingAccumulateOpSrc16(t *testing.T)  { testAcc(t, flIn16, flMask16, "src") }
+func TestFloatingAccumulateMask16(t *testing.T)   { testAcc(t, flIn16, flMask16, "mask") }
+
+func testAcc(t *testing.T, in interface{}, mask []uint32, op string) {
+	maxN := 0
+	switch in := in.(type) {
+	case []uint32:
+		maxN = len(in)
+	case []float32:
+		maxN = len(in)
+	}
+
+	for _, n := range []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
+		33, 55, 79, 96, 120, 165, 256, maxN} {
+
+		if n > maxN {
+			continue
+		}
+
+		var (
+			got8, want8   []uint8
+			got32, want32 []uint32
+		)
+		switch op {
+		case "over":
+			const background = 0x40
+			got8 = make([]uint8, n)
+			for i := range got8 {
+				got8[i] = background
+			}
+			want8 = make([]uint8, n)
+			for i := range want8 {
+				dstA := uint32(background * 0x101)
+				maskA := mask[i]
+				outA := dstA*(0xffff-maskA)/0xffff + maskA
+				want8[i] = uint8(outA >> 8)
+			}
+
+		case "src":
+			got8 = make([]uint8, n)
+			want8 = make([]uint8, n)
+			for i := range want8 {
+				want8[i] = uint8(mask[i] >> 8)
+			}
+
+		case "mask":
+			got32 = make([]uint32, n)
+			want32 = mask[:n]
+		}
+
+		switch in := in.(type) {
+		case []uint32:
+			switch op {
+			case "over":
+				fixedAccumulateOpOver(got8, in[:n])
+			case "src":
+				fixedAccumulateOpSrc(got8, in[:n])
+			case "mask":
+				copy(got32, in[:n])
+				fixedAccumulateMask(got32)
+			}
+		case []float32:
+			switch op {
+			case "over":
+				floatingAccumulateOpOver(got8, in[:n])
+			case "src":
+				floatingAccumulateOpSrc(got8, in[:n])
+			case "mask":
+				floatingAccumulateMask(got32, in[:n])
+			}
+		}
+
+		if op != "mask" {
+			if !bytes.Equal(got8, want8) {
+				t.Errorf("n=%d:\ngot:  % x\nwant: % x", n, got8, want8)
+			}
+		} else {
+			if !uint32sEqual(got32, want32) {
+				t.Errorf("n=%d:\ngot:  % x\nwant: % x", n, got32, want32)
+			}
+		}
+	}
+}
+
+func uint32sEqual(xs, ys []uint32) bool {
+	if len(xs) != len(ys) {
+		return false
+	}
+	for i := range xs {
+		if xs[i] != ys[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func float32sEqual(xs, ys []float32) bool {
+	if len(xs) != len(ys) {
+		return false
+	}
+	for i := range xs {
+		if xs[i] != ys[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func BenchmarkFixedAccumulateOpOver16(b *testing.B)    { benchAcc(b, fxIn16, "over") }
+func BenchmarkFixedAccumulateOpSrc16(b *testing.B)     { benchAcc(b, fxIn16, "src") }
+func BenchmarkFixedAccumulateMask16(b *testing.B)      { benchAcc(b, fxIn16, "mask") }
+func BenchmarkFloatingAccumulateOpOver16(b *testing.B) { benchAcc(b, flIn16, "over") }
+func BenchmarkFloatingAccumulateOpSrc16(b *testing.B)  { benchAcc(b, flIn16, "src") }
+func BenchmarkFloatingAccumulateMask16(b *testing.B)   { benchAcc(b, flIn16, "mask") }
+
+func BenchmarkFixedAccumulateOpOver64(b *testing.B)    { benchAcc(b, fxIn64, "over") }
+func BenchmarkFixedAccumulateOpSrc64(b *testing.B)     { benchAcc(b, fxIn64, "src") }
+func BenchmarkFixedAccumulateMask64(b *testing.B)      { benchAcc(b, fxIn64, "mask") }
+func BenchmarkFloatingAccumulateOpOver64(b *testing.B) { benchAcc(b, flIn64, "over") }
+func BenchmarkFloatingAccumulateOpSrc64(b *testing.B)  { benchAcc(b, flIn64, "src") }
+func BenchmarkFloatingAccumulateMask64(b *testing.B)   { benchAcc(b, flIn64, "mask") }
+
+func benchAcc(b *testing.B, in interface{}, op string) {
+	var f func()
+
+	switch in := in.(type) {
+	case []uint32:
+		switch op {
+		case "over":
+			dst := make([]uint8, len(in))
+			f = func() { fixedAccumulateOpOver(dst, in) }
+		case "src":
+			dst := make([]uint8, len(in))
+			f = func() { fixedAccumulateOpSrc(dst, in) }
+		case "mask":
+			buf := make([]uint32, len(in))
+			copy(buf, in)
+			f = func() { fixedAccumulateMask(buf) }
+		}
+	case []float32:
+		switch op {
+		case "over":
+			dst := make([]uint8, len(in))
+			f = func() { floatingAccumulateOpOver(dst, in) }
+		case "src":
+			dst := make([]uint8, len(in))
+			f = func() { floatingAccumulateOpSrc(dst, in) }
+		case "mask":
+			dst := make([]uint32, len(in))
+			f = func() { floatingAccumulateMask(dst, in) }
+		}
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		f()
+	}
+}
+
+// itou exists because "uint32(int2ϕ(-1))" doesn't compile: constant -1
+// overflows uint32.
+func itou(i int2ϕ) uint32 {
+	return uint32(i)
+}
+
+var fxInShort = []uint32{
+	itou(+0x020000), // +0.125, // Running sum: +0.125
+	itou(-0x080000), // -0.500, // Running sum: -0.375
+	itou(+0x040000), // +0.250, // Running sum: -0.125
+	itou(+0x060000), // +0.375, // Running sum: +0.250
+	itou(+0x020000), // +0.125, // Running sum: +0.375
+	itou(+0x000000), // +0.000, // Running sum: +0.375
+	itou(-0x100000), // -1.000, // Running sum: -0.625
+	itou(-0x080000), // -0.500, // Running sum: -1.125
+	itou(+0x040000), // +0.250, // Running sum: -0.875
+	itou(+0x0e0000), // +0.875, // Running sum: +0.000
+	itou(+0x040000), // +0.250, // Running sum: +0.250
+	itou(+0x0c0000), // +0.750, // Running sum: +1.000
+}
+
+var flInShort = []float32{
+	+0.125, // Running sum: +0.125
+	-0.500, // Running sum: -0.375
+	+0.250, // Running sum: -0.125
+	+0.375, // Running sum: +0.250
+	+0.125, // Running sum: +0.375
+	+0.000, // Running sum: +0.375
+	-1.000, // Running sum: -0.625
+	-0.500, // Running sum: -1.125
+	+0.250, // Running sum: -0.875
+	+0.875, // Running sum: +0.000
+	+0.250, // Running sum: +0.250
+	+0.750, // Running sum: +1.000
+}
+
+// It's OK for fxMaskShort and flMaskShort to have slightly different values.
+// Both the fixed and floating point implementations already have (different)
+// rounding errors in the xxxLineTo methods before we get to accumulation. It's
+// OK for 50% coverage (in ideal math) to be approximated by either 0x7fff or
+// 0x8000. Both slices do contain checks that 0% and 100% map to 0x0000 and
+// 0xffff, as does checkCornersCenter in vector_test.go.
+//
+// It is important, though, for the SIMD and non-SIMD fixed point
+// implementations to give the exact same output, and likewise for the floating
+// point implementations.
+
+var fxMaskShort = []uint32{
+	0x2000,
+	0x6000,
+	0x2000,
+	0x4000,
+	0x6000,
+	0x6000,
+	0xa000,
+	0xffff,
+	0xe000,
+	0x0000,
+	0x4000,
+	0xffff,
+}
+
+var flMaskShort = []uint32{
+	0x1fff,
+	0x5fff,
+	0x1fff,
+	0x3fff,
+	0x5fff,
+	0x5fff,
+	0x9fff,
+	0xffff,
+	0xdfff,
+	0x0000,
+	0x3fff,
+	0xffff,
+}
+
+func TestMakeFxInXxx(t *testing.T) {
+	dump := func(us []uint32) string {
+		var b bytes.Buffer
+		for i, u := range us {
+			if i%8 == 0 {
+				b.WriteByte('\n')
+			}
+			fmt.Fprintf(&b, "%#08x, ", u)
+		}
+		return b.String()
+	}
+
+	if !uint32sEqual(fxIn16, hardCodedFxIn16) {
+		t.Errorf("height 16: got:%v\nwant:%v", dump(fxIn16), dump(hardCodedFxIn16))
+	}
+}
+
+func TestMakeFlInXxx(t *testing.T) {
+	dump := func(fs []float32) string {
+		var b bytes.Buffer
+		for i, f := range fs {
+			if i%8 == 0 {
+				b.WriteByte('\n')
+			}
+			fmt.Fprintf(&b, "%v, ", f)
+		}
+		return b.String()
+	}
+
+	if !float32sEqual(flIn16, hardCodedFlIn16) {
+		t.Errorf("height 16: got:%v\nwant:%v", dump(flIn16), dump(hardCodedFlIn16))
+	}
+}
+
+func makeInXxx(height int, useFloatingPointMath bool) *Rasterizer {
+	width, data := scaledBenchmarkGlyphData(height)
+	z := NewRasterizer(width, height)
+	z.setUseFloatingPointMath(useFloatingPointMath)
+	for _, d := range data {
+		switch d.n {
+		case 0:
+			z.MoveTo(d.p)
+		case 1:
+			z.LineTo(d.p)
+		case 2:
+			z.QuadTo(d.p, d.q)
+		}
+	}
+	return z
+}
+
+func makeFxInXxx(height int) []uint32 {
+	z := makeInXxx(height, false)
+	return z.bufU32
+}
+
+func makeFlInXxx(height int) []float32 {
+	z := makeInXxx(height, true)
+	return z.bufF32
+}
+
+// fxInXxx and flInXxx are the z.bufU32 and z.bufF32 inputs to the accumulate
+// functions when rasterizing benchmarkGlyphData at a height of Xxx pixels.
+//
+// fxMaskXxx and flMaskXxx are the corresponding golden outputs of those
+// accumulateMask functions.
+//
+// The hardCodedEtc versions are a sanity check for unexpected changes in the
+// rasterization implementations up to but not including accumulation.
+
+var (
+	fxIn16 = makeFxInXxx(16)
+	fxIn64 = makeFxInXxx(64)
+	flIn16 = makeFlInXxx(16)
+	flIn64 = makeFlInXxx(64)
+)
+
+var hardCodedFxIn16 = []uint32{
+	0x00000000, 0x00000000, 0xffffa3ee, 0xfff9f0c9, 0xfffaaafc, 0xfffd38ec, 0xffff073f, 0x0001dddf,
+	0x0002589a, 0x0006a22c, 0x0004a6df, 0x000000a0, 0x00000000, 0x00000000, 0xfffdb883, 0xfff4c620,
+	0xfffd815f, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00052ec6,
+	0x000ab1ba, 0x00001f7f, 0xffff29b7, 0xfff2ad44, 0xfffe2906, 0x00006c84, 0x0006ce82, 0x00050d7b,
+	0x00010db4, 0xfffd8c05, 0xfff85159, 0xfffccc6d, 0x00000000, 0x00088d28, 0x000772d8, 0xfff8a36a,
+	0xfff75c96, 0x00000000, 0x000a2b80, 0x0005d480, 0x00000000, 0x00000000, 0x00000000, 0xffff4bbf,
+	0xfff2b937, 0xfffdfb0b, 0x0001cc00, 0x000e3400, 0xfffa4980, 0xfffcb680, 0x000008e8, 0x0008966f,
+	0x000060a8, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0xfff72000, 0xfff8e000, 0x00000165,
+	0x000e9134, 0x00016d65, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000,
+	0x00000000, 0x00000000, 0xfff8d3be, 0xfff72c42, 0x00000000, 0x000cec0f, 0x000313f1, 0x00000000,
+	0x00000000, 0xfffe84f1, 0xfffbbb8f, 0xfffe3008, 0xfffe311b, 0xffff1e60, 0x00000000, 0xfffd6f10,
+	0xfffcd0f0, 0x00000000, 0x000cec00, 0x00031400, 0xfffe6d8a, 0xfff7d307, 0xfffa38bf, 0xffff86b3,
+	0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x000cec00,
+	0x00024dc4, 0xfff3cc79, 0xfffcf9c4, 0x00003ed0, 0x000467df, 0x0004c32f, 0x0001a038, 0x00012964,
+	0x00002883, 0xfffa7bf1, 0xfff9280f, 0x00000000, 0x000cec00, 0xfffa2901, 0xfff8eaff, 0x00004138,
+	0x000aebd5, 0x0004d2f2, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0xfff8dc00, 0xfff72400,
+	0x00000000, 0x000cec00, 0xfff64800, 0xfffccc00, 0x00039400, 0x000c6c00, 0x00000000, 0x00000000,
+	0x00000000, 0x00000000, 0x00000000, 0xfff8dc00, 0xfff72400, 0x00000000, 0x000cec00, 0xfff3ea8a,
+	0xffff2976, 0x00047cad, 0x000b8353, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000,
+	0xfff6cb2e, 0xfff934d2, 0x00000000, 0x000cec00, 0xfff68000, 0xfffc9400, 0x0000babf, 0x000cfbcc,
+	0x00024974, 0x00000000, 0x00000000, 0x00000000, 0xfffa12a1, 0xfff61e13, 0xffffcf4d, 0x00000000,
+	0x000c79a0, 0xfffcac8c, 0xfff6d9d4, 0x00000000, 0x00015024, 0x0006d297, 0x000288dc, 0xfffe8e52,
+	0xfffaba3a, 0xfffc0cbd, 0xffffff20, 0x00000000, 0x00000000, 0x000b5c00, 0x000496d7, 0xfff5a25f,
+	0xfffa6acc, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x0002abf1, 0x0005195f,
+	0xfff83aae, 0x00000000, 0x00089fb6, 0x0007604a, 0xfffffe47, 0xfffb0173, 0xfff94d6b, 0xfffd7586,
+	0xffff5219, 0x000319cc, 0x0003eed3, 0x0007529f, 0xfffedc08, 0xfff647f6, 0x00000000, 0x000392ce,
+}
+
+var hardCodedFlIn16 = []float32{
+	0, 0, -0.022306755, -0.3782405, -0.33334962, -0.1741521, -0.0607556, 0.11660573,
+	0.14664596, 0.41462868, 0.2907673, 0.0001568835, 0, 0, -0.14239307, -0.7012868,
+	-0.15632017, 0, 0, 0, 0, 0, 0, 0.3230303,
+	0.6690931, 0.007876594, -0.05189419, -0.832786, -0.11531975, 0.026225802, 0.42518616, 0.3154636,
+	0.06598757, -0.15304244, -0.47969276, -0.20012794, 0, 0.5327272, 0.46727282, -0.45950258,
+	-0.5404974, 0, 0.63484025, 0.36515975, 0, 0, 0, -0.04351709,
+	-0.8293345, -0.12714837, 0.11087036, 0.88912964, -0.35792422, -0.2053554, 0.0022513224, 0.5374398,
+	0.023588525, 0, 0, 0, 0, -0.55346966, -0.44653034, 0.0002531938,
+	0.9088273, 0.090919495, 0, 0, 0, 0, 0, 0,
+	0, 0, -0.44745448, -0.5525455, 0, 0.80748945, 0.19251058, 0,
+	0, -0.092476256, -0.2661464, -0.11322958, -0.11298219, -0.055094406, 0, -0.16045958,
+	-0.1996116, 0, 0.80748653, 0.19251347, -0.09804727, -0.51129663, -0.3610403, -0.029615778,
+	0, 0, 0, 0, 0, 0, 0, 0.80748653,
+	0.14411622, -0.76251525, -0.1890875, 0.01527351, 0.27528667, 0.29730347, 0.101477206, 0.07259522,
+	0.009900213, -0.34395567, -0.42788061, 0, 0.80748653, -0.3648737, -0.44261283, 0.015778137,
+	0.6826565, 0.30156538, 0, 0, 0, 0, -0.44563293, -0.55436707,
+	0, 0.80748653, -0.60703933, -0.20044717, 0.22371745, 0.77628255, 0, 0,
+	0, 0, 0, -0.44563293, -0.55436707, 0, 0.80748653, -0.7550391,
+	-0.05244744, 0.2797074, 0.72029257, 0, 0, 0, 0, 0,
+	-0.57440215, -0.42559785, 0, 0.80748653, -0.59273535, -0.21475118, 0.04544862, 0.81148535,
+	0.14306602, 0, 0, 0, -0.369642, -0.61841226, -0.011945802, 0,
+	0.7791623, -0.20691396, -0.57224834, 0, 0.08218567, 0.42637306, 0.1586175, -0.089709565,
+	-0.32935485, -0.24788953, -0.00022224105, 0, 0, 0.7085409, 0.28821066, -0.64765793,
+	-0.34909368, 0, 0, 0, 0, 0, 0.16679136, 0.31914657,
+	-0.48593786, 0, 0.537915, 0.462085, -0.00041967133, -0.3120329, -0.41914812, -0.15886839,
+	-0.042683028, 0.19370951, 0.24624406, 0.45803425, -0.07049577, -0.6091341, 0, 0.22253075,
+}
+
+var fxMask16 = []uint32{
+	0x0000, 0x0000, 0x05c1, 0x66b4, 0xbc04, 0xe876, 0xf802, 0xda24, 0xb49a, 0x4a77, 0x0009, 0x0000, 0x0000,
+	0x0000, 0x2477, 0xd815, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xad13, 0x01f7, 0x0000,
+	0x0d64, 0xe290, 0xffff, 0xf937, 0x8c4f, 0x3b77, 0x2a9c, 0x51dc, 0xccc6, 0xffff, 0xffff, 0x772d, 0x0000,
+	0x75c9, 0xffff, 0xffff, 0x5d47, 0x0000, 0x0000, 0x0000, 0x0000, 0x0b43, 0xdfb0, 0xffff, 0xe33f, 0x0000,
+	0x5b67, 0x8fff, 0x8f71, 0x060a, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x8dff, 0xffff, 0xffe9, 0x16d6,
+	0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x72c4, 0xffff, 0xffff, 0x313e,
+	0x0000, 0x0000, 0x0000, 0x17b0, 0x5bf7, 0x78f7, 0x95e5, 0xa3ff, 0xa3ff, 0xcd0e, 0xffff, 0xffff, 0x313f,
+	0x0000, 0x1927, 0x9bf6, 0xf86a, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0x313f,
+	0x0c63, 0xcf9b, 0xffff, 0xfc12, 0xb594, 0x6961, 0x4f5e, 0x3cc7, 0x3a3f, 0x9280, 0xffff, 0xffff, 0x313f,
+	0x8eaf, 0xffff, 0xfbec, 0x4d2e, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x723f, 0xffff, 0xffff, 0x313f,
+	0xccbf, 0xffff, 0xc6bf, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x723f, 0xffff, 0xffff, 0x313f,
+	0xf297, 0xffff, 0xb834, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x934c, 0xffff, 0xffff, 0x313f,
+	0xc93f, 0xffff, 0xf453, 0x2497, 0x0000, 0x0000, 0x0000, 0x0000, 0x5ed5, 0xfcf4, 0xffff, 0xffff, 0x3865,
+	0x6d9c, 0xffff, 0xffff, 0xeafd, 0x7dd4, 0x5546, 0x6c61, 0xc0bd, 0xfff1, 0xffff, 0xffff, 0xffff, 0x4a3f,
+	0x00d2, 0xa6ac, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xd540, 0x83aa, 0xffff, 0xffff, 0x7604,
+	0x0000, 0x001b, 0x5004, 0xbb2d, 0xe3d5, 0xeeb3, 0xbd16, 0x7e29, 0x08ff, 0x1b3f, 0xb6bf, 0xb6bf, 0x7d92,
+}
+
+var flMask16 = []uint32{
+	0x0000, 0x0000, 0x05b5, 0x668a, 0xbbe0, 0xe875, 0xf803, 0xda29, 0xb49f, 0x4a7a, 0x000a, 0x0000, 0x0000,
+	0x0000, 0x2473, 0xd7fb, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xad4d, 0x0204, 0x0000,
+	0x0d48, 0xe27a, 0xffff, 0xf949, 0x8c70, 0x3bae, 0x2ac9, 0x51f7, 0xccc4, 0xffff, 0xffff, 0x779f, 0x0000,
+	0x75a1, 0xffff, 0xffff, 0x5d7b, 0x0000, 0x0000, 0x0000, 0x0000, 0x0b23, 0xdf73, 0xffff, 0xe39d, 0x0000,
+	0x5ba0, 0x9033, 0x8f9f, 0x0609, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x8db0, 0xffff, 0xffef, 0x1746,
+	0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x728c, 0xffff, 0xffff, 0x3148,
+	0x0000, 0x0000, 0x0000, 0x17ac, 0x5bce, 0x78cb, 0x95b7, 0xa3d2, 0xa3d2, 0xcce6, 0xffff, 0xffff, 0x3148,
+	0x0000, 0x1919, 0x9bfd, 0xf86b, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0x3148,
+	0x0c63, 0xcf97, 0xffff, 0xfc17, 0xb59d, 0x6981, 0x4f87, 0x3cf1, 0x3a68, 0x9276, 0xffff, 0xffff, 0x3148,
+	0x8eb0, 0xffff, 0xfbf5, 0x4d33, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x7214, 0xffff, 0xffff, 0x3148,
+	0xccaf, 0xffff, 0xc6ba, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x7214, 0xffff, 0xffff, 0x3148,
+	0xf292, 0xffff, 0xb865, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x930c, 0xffff, 0xffff, 0x3148,
+	0xc906, 0xffff, 0xf45d, 0x249f, 0x0000, 0x0000, 0x0000, 0x0000, 0x5ea0, 0xfcf1, 0xffff, 0xffff, 0x3888,
+	0x6d81, 0xffff, 0xffff, 0xeaf5, 0x7dcf, 0x5533, 0x6c2b, 0xc07b, 0xfff1, 0xffff, 0xffff, 0xffff, 0x4a9d,
+	0x00d4, 0xa6a1, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xffff, 0xd54d, 0x8399, 0xffff, 0xffff, 0x764b,
+	0x0000, 0x001b, 0x4ffc, 0xbb4a, 0xe3f5, 0xeee3, 0xbd4c, 0x7e42, 0x0900, 0x1b0c, 0xb6fc, 0xb6fc, 0x7e04,
+}
diff --git a/vector/vector.go b/vector/vector.go
index e0879f6..4813832 100644
--- a/vector/vector.go
+++ b/vector/vector.go
@@ -123,11 +123,15 @@
 	z.pen = f32.Vec2{}
 	z.DrawOp = draw.Over
 
-	z.useFloatingPointMath = w > floatingPointMathThreshold || h > floatingPointMathThreshold
+	z.setUseFloatingPointMath(w > floatingPointMathThreshold || h > floatingPointMathThreshold)
+}
 
-	// Make z.bufF32 or z.bufU32 large enough to hold w*h samples.
+func (z *Rasterizer) setUseFloatingPointMath(b bool) {
+	z.useFloatingPointMath = b
+
+	// Make z.bufF32 or z.bufU32 large enough to hold width * height samples.
 	if z.useFloatingPointMath {
-		if n := w * h; n > cap(z.bufF32) {
+		if n := z.size.X * z.size.Y; n > cap(z.bufF32) {
 			z.bufF32 = make([]float32, n)
 		} else {
 			z.bufF32 = z.bufF32[:n]
@@ -136,7 +140,7 @@
 			}
 		}
 	} else {
-		if n := w * h; n > cap(z.bufU32) {
+		if n := z.size.X * z.size.Y; n > cap(z.bufU32) {
 			z.bufU32 = make([]uint32, n)
 		} else {
 			z.bufU32 = z.bufU32[:n]
diff --git a/vector/vector_test.go b/vector/vector_test.go
index 8bf5e1e..8e9191f 100644
--- a/vector/vector_test.go
+++ b/vector/vector_test.go
@@ -294,14 +294,16 @@
 	benchmarkGlyphHeight = 1122
 )
 
-// benchmarkGlyphData is the 'a' glyph from the Roboto Regular font, translated
-// so that its top left corner is (0, 0).
-var benchmarkGlyphData = []struct {
+type benchmarkGlyphDatum struct {
 	// n being 0, 1 or 2 means moveTo, lineTo or quadTo.
 	n uint32
 	p f32.Vec2
 	q f32.Vec2
-}{
+}
+
+// benchmarkGlyphData is the 'a' glyph from the Roboto Regular font, translated
+// so that its top left corner is (0, 0).
+var benchmarkGlyphData = []benchmarkGlyphDatum{
 	{0, f32.Vec2{699, 1102}, f32.Vec2{0, 0}},
 	{2, f32.Vec2{683, 1070}, f32.Vec2{673, 988}},
 	{2, f32.Vec2{544, 1122}, f32.Vec2{365, 1122}},
@@ -335,16 +337,11 @@
 	{2, f32.Vec2{301, 961}, f32.Vec2{392, 961}},
 }
 
-// benchGlyph benchmarks rasterizing a TrueType glyph.
-//
-// Note that, compared to the github.com/google/font-go prototype, the height
-// here is the height of the bounding box, not the pixels per em used to scale
-// a glyph's vectors. A height of 64 corresponds to a ppem greater than 64.
-func benchGlyph(b *testing.B, colorModel byte, loose bool, height int, op draw.Op) {
+func scaledBenchmarkGlyphData(height int) (width int, data []benchmarkGlyphDatum) {
 	scale := float32(height) / benchmarkGlyphHeight
 
 	// Clone the benchmarkGlyphData slice and scale its coordinates.
-	data := append(benchmarkGlyphData[:0:0], benchmarkGlyphData...)
+	data = append(data, benchmarkGlyphData...)
 	for i := range data {
 		data[i].p[0] *= scale
 		data[i].p[1] *= scale
@@ -352,7 +349,16 @@
 		data[i].q[1] *= scale
 	}
 
-	width := int(math.Ceil(float64(benchmarkGlyphWidth * scale)))
+	return int(math.Ceil(float64(benchmarkGlyphWidth * scale))), data
+}
+
+// benchGlyph benchmarks rasterizing a TrueType glyph.
+//
+// Note that, compared to the github.com/google/font-go prototype, the height
+// here is the height of the bounding box, not the pixels per em used to scale
+// a glyph's vectors. A height of 64 corresponds to a ppem greater than 64.
+func benchGlyph(b *testing.B, colorModel byte, loose bool, height int, op draw.Op) {
+	width, data := scaledBenchmarkGlyphData(height)
 	z := NewRasterizer(width, height)
 
 	bounds := z.Bounds()