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-rw-r--r--vendor/golang.org/x/image/vector/vector.go472
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diff --git a/vendor/golang.org/x/image/vector/vector.go b/vendor/golang.org/x/image/vector/vector.go
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+// 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.
+
+//go:generate go run gen.go
+//go:generate asmfmt -w acc_amd64.s
+
+// asmfmt is https://github.com/klauspost/asmfmt
+
+// Package vector provides a rasterizer for 2-D vector graphics.
+package vector // import "golang.org/x/image/vector"
+
+// The rasterizer's design follows
+// https://medium.com/@raphlinus/inside-the-fastest-font-renderer-in-the-world-75ae5270c445
+//
+// Proof of concept code is in
+// https://github.com/google/font-go
+//
+// See also:
+// http://nothings.org/gamedev/rasterize/
+// http://projects.tuxee.net/cl-vectors/section-the-cl-aa-algorithm
+// https://people.gnome.org/~mathieu/libart/internals.html#INTERNALS-SCANLINE
+
+import (
+ "image"
+ "image/color"
+ "image/draw"
+ "math"
+)
+
+// floatingPointMathThreshold is the width or height above which the rasterizer
+// chooses to used floating point math instead of fixed point math.
+//
+// Both implementations of line segmentation rasterization (see raster_fixed.go
+// and raster_floating.go) implement the same algorithm (in ideal, infinite
+// precision math) but they perform differently in practice. The fixed point
+// math version is roughtly 1.25x faster (on GOARCH=amd64) on the benchmarks,
+// but at sufficiently large scales, the computations will overflow and hence
+// show rendering artifacts. The floating point math version has more
+// consistent quality over larger scales, but it is significantly slower.
+//
+// This constant determines when to use the faster implementation and when to
+// use the better quality implementation.
+//
+// The rationale for this particular value is that TestRasterizePolygon in
+// vector_test.go checks the rendering quality of polygon edges at various
+// angles, inscribed in a circle of diameter 512. It may be that a higher value
+// would still produce acceptable quality, but 512 seems to work.
+const floatingPointMathThreshold = 512
+
+func lerp(t, px, py, qx, qy float32) (x, y float32) {
+ return px + t*(qx-px), py + t*(qy-py)
+}
+
+func clamp(i, width int32) uint {
+ if i < 0 {
+ return 0
+ }
+ if i < width {
+ return uint(i)
+ }
+ return uint(width)
+}
+
+// NewRasterizer returns a new Rasterizer whose rendered mask image is bounded
+// by the given width and height.
+func NewRasterizer(w, h int) *Rasterizer {
+ z := &Rasterizer{}
+ z.Reset(w, h)
+ return z
+}
+
+// Raster is a 2-D vector graphics rasterizer.
+//
+// The zero value is usable, in that it is a Rasterizer whose rendered mask
+// image has zero width and zero height. Call Reset to change its bounds.
+type Rasterizer struct {
+ // bufXxx are buffers of float32 or uint32 values, holding either the
+ // individual or cumulative area values.
+ //
+ // We don't actually need both values at any given time, and to conserve
+ // memory, the integration of the individual to the cumulative could modify
+ // the buffer in place. In other words, we could use a single buffer, say
+ // of type []uint32, and add some math.Float32bits and math.Float32frombits
+ // calls to satisfy the compiler's type checking. As of Go 1.7, though,
+ // there is a performance penalty between:
+ // bufF32[i] += x
+ // and
+ // bufU32[i] = math.Float32bits(x + math.Float32frombits(bufU32[i]))
+ //
+ // See golang.org/issue/17220 for some discussion.
+ bufF32 []float32
+ bufU32 []uint32
+
+ useFloatingPointMath bool
+
+ size image.Point
+ firstX float32
+ firstY float32
+ penX float32
+ penY float32
+
+ // DrawOp is the operator used for the Draw method.
+ //
+ // The zero value is draw.Over.
+ DrawOp draw.Op
+
+ // TODO: an exported field equivalent to the mask point in the
+ // draw.DrawMask function in the stdlib image/draw package?
+}
+
+// Reset resets a Rasterizer as if it was just returned by NewRasterizer.
+//
+// This includes setting z.DrawOp to draw.Over.
+func (z *Rasterizer) Reset(w, h int) {
+ z.size = image.Point{w, h}
+ z.firstX = 0
+ z.firstY = 0
+ z.penX = 0
+ z.penY = 0
+ z.DrawOp = draw.Over
+
+ z.setUseFloatingPointMath(w > floatingPointMathThreshold || h > floatingPointMathThreshold)
+}
+
+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 := z.size.X * z.size.Y; n > cap(z.bufF32) {
+ z.bufF32 = make([]float32, n)
+ } else {
+ z.bufF32 = z.bufF32[:n]
+ for i := range z.bufF32 {
+ z.bufF32[i] = 0
+ }
+ }
+ } else {
+ if n := z.size.X * z.size.Y; n > cap(z.bufU32) {
+ z.bufU32 = make([]uint32, n)
+ } else {
+ z.bufU32 = z.bufU32[:n]
+ for i := range z.bufU32 {
+ z.bufU32[i] = 0
+ }
+ }
+ }
+}
+
+// Size returns the width and height passed to NewRasterizer or Reset.
+func (z *Rasterizer) Size() image.Point {
+ return z.size
+}
+
+// Bounds returns the rectangle from (0, 0) to the width and height passed to
+// NewRasterizer or Reset.
+func (z *Rasterizer) Bounds() image.Rectangle {
+ return image.Rectangle{Max: z.size}
+}
+
+// Pen returns the location of the path-drawing pen: the last argument to the
+// most recent XxxTo call.
+func (z *Rasterizer) Pen() (x, y float32) {
+ return z.penX, z.penY
+}
+
+// ClosePath closes the current path.
+func (z *Rasterizer) ClosePath() {
+ z.LineTo(z.firstX, z.firstY)
+}
+
+// MoveTo starts a new path and moves the pen to (ax, ay).
+//
+// The coordinates are allowed to be out of the Rasterizer's bounds.
+func (z *Rasterizer) MoveTo(ax, ay float32) {
+ z.firstX = ax
+ z.firstY = ay
+ z.penX = ax
+ z.penY = ay
+}
+
+// LineTo adds a line segment, from the pen to (bx, by), and moves the pen to
+// (bx, by).
+//
+// The coordinates are allowed to be out of the Rasterizer's bounds.
+func (z *Rasterizer) LineTo(bx, by float32) {
+ if z.useFloatingPointMath {
+ z.floatingLineTo(bx, by)
+ } else {
+ z.fixedLineTo(bx, by)
+ }
+}
+
+// QuadTo adds a quadratic Bézier segment, from the pen via (bx, by) to (cx,
+// cy), and moves the pen to (cx, cy).
+//
+// The coordinates are allowed to be out of the Rasterizer's bounds.
+func (z *Rasterizer) QuadTo(bx, by, cx, cy float32) {
+ ax, ay := z.penX, z.penY
+ devsq := devSquared(ax, ay, bx, by, cx, cy)
+ if devsq >= 0.333 {
+ const tol = 3
+ n := 1 + int(math.Sqrt(math.Sqrt(tol*float64(devsq))))
+ t, nInv := float32(0), 1/float32(n)
+ for i := 0; i < n-1; i++ {
+ t += nInv
+ abx, aby := lerp(t, ax, ay, bx, by)
+ bcx, bcy := lerp(t, bx, by, cx, cy)
+ z.LineTo(lerp(t, abx, aby, bcx, bcy))
+ }
+ }
+ z.LineTo(cx, cy)
+}
+
+// CubeTo adds a cubic Bézier segment, from the pen via (bx, by) and (cx, cy)
+// to (dx, dy), and moves the pen to (dx, dy).
+//
+// The coordinates are allowed to be out of the Rasterizer's bounds.
+func (z *Rasterizer) CubeTo(bx, by, cx, cy, dx, dy float32) {
+ ax, ay := z.penX, z.penY
+ devsq := devSquared(ax, ay, bx, by, dx, dy)
+ if devsqAlt := devSquared(ax, ay, cx, cy, dx, dy); devsq < devsqAlt {
+ devsq = devsqAlt
+ }
+ if devsq >= 0.333 {
+ const tol = 3
+ n := 1 + int(math.Sqrt(math.Sqrt(tol*float64(devsq))))
+ t, nInv := float32(0), 1/float32(n)
+ for i := 0; i < n-1; i++ {
+ t += nInv
+ abx, aby := lerp(t, ax, ay, bx, by)
+ bcx, bcy := lerp(t, bx, by, cx, cy)
+ cdx, cdy := lerp(t, cx, cy, dx, dy)
+ abcx, abcy := lerp(t, abx, aby, bcx, bcy)
+ bcdx, bcdy := lerp(t, bcx, bcy, cdx, cdy)
+ z.LineTo(lerp(t, abcx, abcy, bcdx, bcdy))
+ }
+ }
+ z.LineTo(dx, dy)
+}
+
+// devSquared returns a measure of how curvy the sequence (ax, ay) to (bx, by)
+// to (cx, cy) is. It determines how many line segments will approximate a
+// Bézier curve segment.
+//
+// http://lists.nongnu.org/archive/html/freetype-devel/2016-08/msg00080.html
+// gives the rationale for this evenly spaced heuristic instead of a recursive
+// de Casteljau approach:
+//
+// The reason for the subdivision by n is that I expect the "flatness"
+// computation to be semi-expensive (it's done once rather than on each
+// potential subdivision) and also because you'll often get fewer subdivisions.
+// Taking a circular arc as a simplifying assumption (ie a spherical cow),
+// where I get n, a recursive approach would get 2^⌈lg n⌉, which, if I haven't
+// made any horrible mistakes, is expected to be 33% more in the limit.
+func devSquared(ax, ay, bx, by, cx, cy float32) float32 {
+ devx := ax - 2*bx + cx
+ devy := ay - 2*by + cy
+ return devx*devx + devy*devy
+}
+
+// Draw implements the Drawer interface from the standard library's image/draw
+// package.
+//
+// The vector paths previously added via the XxxTo calls become the mask for
+// drawing src onto dst.
+func (z *Rasterizer) Draw(dst draw.Image, r image.Rectangle, src image.Image, sp image.Point) {
+ // TODO: adjust r and sp (and mp?) if src.Bounds() doesn't contain
+ // r.Add(sp.Sub(r.Min)).
+
+ if src, ok := src.(*image.Uniform); ok {
+ srcR, srcG, srcB, srcA := src.RGBA()
+ switch dst := dst.(type) {
+ case *image.Alpha:
+ // Fast path for glyph rendering.
+ if srcA == 0xffff {
+ if z.DrawOp == draw.Over {
+ z.rasterizeDstAlphaSrcOpaqueOpOver(dst, r)
+ } else {
+ z.rasterizeDstAlphaSrcOpaqueOpSrc(dst, r)
+ }
+ return
+ }
+ case *image.RGBA:
+ if z.DrawOp == draw.Over {
+ z.rasterizeDstRGBASrcUniformOpOver(dst, r, srcR, srcG, srcB, srcA)
+ } else {
+ z.rasterizeDstRGBASrcUniformOpSrc(dst, r, srcR, srcG, srcB, srcA)
+ }
+ return
+ }
+ }
+
+ if z.DrawOp == draw.Over {
+ z.rasterizeOpOver(dst, r, src, sp)
+ } else {
+ z.rasterizeOpSrc(dst, r, src, sp)
+ }
+}
+
+func (z *Rasterizer) accumulateMask() {
+ if z.useFloatingPointMath {
+ if n := z.size.X * z.size.Y; n > cap(z.bufU32) {
+ z.bufU32 = make([]uint32, n)
+ } else {
+ z.bufU32 = z.bufU32[:n]
+ }
+ if haveFloatingAccumulateSIMD {
+ floatingAccumulateMaskSIMD(z.bufU32, z.bufF32)
+ } else {
+ floatingAccumulateMask(z.bufU32, z.bufF32)
+ }
+ } else {
+ if haveFixedAccumulateSIMD {
+ fixedAccumulateMaskSIMD(z.bufU32)
+ } else {
+ fixedAccumulateMask(z.bufU32)
+ }
+ }
+}
+
+func (z *Rasterizer) rasterizeDstAlphaSrcOpaqueOpOver(dst *image.Alpha, r image.Rectangle) {
+ // TODO: non-zero vs even-odd winding?
+ if r == dst.Bounds() && r == z.Bounds() {
+ // We bypass the z.accumulateMask step and convert straight from
+ // z.bufF32 or z.bufU32 to dst.Pix.
+ if z.useFloatingPointMath {
+ if haveFloatingAccumulateSIMD {
+ floatingAccumulateOpOverSIMD(dst.Pix, z.bufF32)
+ } else {
+ floatingAccumulateOpOver(dst.Pix, z.bufF32)
+ }
+ } else {
+ if haveFixedAccumulateSIMD {
+ fixedAccumulateOpOverSIMD(dst.Pix, z.bufU32)
+ } else {
+ fixedAccumulateOpOver(dst.Pix, z.bufU32)
+ }
+ }
+ return
+ }
+
+ z.accumulateMask()
+ pix := dst.Pix[dst.PixOffset(r.Min.X, r.Min.Y):]
+ for y, y1 := 0, r.Max.Y-r.Min.Y; y < y1; y++ {
+ for x, x1 := 0, r.Max.X-r.Min.X; x < x1; x++ {
+ ma := z.bufU32[y*z.size.X+x]
+ i := y*dst.Stride + x
+
+ // This formula is like rasterizeOpOver's, simplified for the
+ // concrete dst type and opaque src assumption.
+ a := 0xffff - ma
+ pix[i] = uint8((uint32(pix[i])*0x101*a/0xffff + ma) >> 8)
+ }
+ }
+}
+
+func (z *Rasterizer) rasterizeDstAlphaSrcOpaqueOpSrc(dst *image.Alpha, r image.Rectangle) {
+ // TODO: non-zero vs even-odd winding?
+ if r == dst.Bounds() && r == z.Bounds() {
+ // We bypass the z.accumulateMask step and convert straight from
+ // z.bufF32 or z.bufU32 to dst.Pix.
+ if z.useFloatingPointMath {
+ if haveFloatingAccumulateSIMD {
+ floatingAccumulateOpSrcSIMD(dst.Pix, z.bufF32)
+ } else {
+ floatingAccumulateOpSrc(dst.Pix, z.bufF32)
+ }
+ } else {
+ if haveFixedAccumulateSIMD {
+ fixedAccumulateOpSrcSIMD(dst.Pix, z.bufU32)
+ } else {
+ fixedAccumulateOpSrc(dst.Pix, z.bufU32)
+ }
+ }
+ return
+ }
+
+ z.accumulateMask()
+ pix := dst.Pix[dst.PixOffset(r.Min.X, r.Min.Y):]
+ for y, y1 := 0, r.Max.Y-r.Min.Y; y < y1; y++ {
+ for x, x1 := 0, r.Max.X-r.Min.X; x < x1; x++ {
+ ma := z.bufU32[y*z.size.X+x]
+
+ // This formula is like rasterizeOpSrc's, simplified for the
+ // concrete dst type and opaque src assumption.
+ pix[y*dst.Stride+x] = uint8(ma >> 8)
+ }
+ }
+}
+
+func (z *Rasterizer) rasterizeDstRGBASrcUniformOpOver(dst *image.RGBA, r image.Rectangle, sr, sg, sb, sa uint32) {
+ z.accumulateMask()
+ pix := dst.Pix[dst.PixOffset(r.Min.X, r.Min.Y):]
+ for y, y1 := 0, r.Max.Y-r.Min.Y; y < y1; y++ {
+ for x, x1 := 0, r.Max.X-r.Min.X; x < x1; x++ {
+ ma := z.bufU32[y*z.size.X+x]
+
+ // This formula is like rasterizeOpOver's, simplified for the
+ // concrete dst type and uniform src assumption.
+ a := 0xffff - (sa * ma / 0xffff)
+ i := y*dst.Stride + 4*x
+ pix[i+0] = uint8(((uint32(pix[i+0])*0x101*a + sr*ma) / 0xffff) >> 8)
+ pix[i+1] = uint8(((uint32(pix[i+1])*0x101*a + sg*ma) / 0xffff) >> 8)
+ pix[i+2] = uint8(((uint32(pix[i+2])*0x101*a + sb*ma) / 0xffff) >> 8)
+ pix[i+3] = uint8(((uint32(pix[i+3])*0x101*a + sa*ma) / 0xffff) >> 8)
+ }
+ }
+}
+
+func (z *Rasterizer) rasterizeDstRGBASrcUniformOpSrc(dst *image.RGBA, r image.Rectangle, sr, sg, sb, sa uint32) {
+ z.accumulateMask()
+ pix := dst.Pix[dst.PixOffset(r.Min.X, r.Min.Y):]
+ for y, y1 := 0, r.Max.Y-r.Min.Y; y < y1; y++ {
+ for x, x1 := 0, r.Max.X-r.Min.X; x < x1; x++ {
+ ma := z.bufU32[y*z.size.X+x]
+
+ // This formula is like rasterizeOpSrc's, simplified for the
+ // concrete dst type and uniform src assumption.
+ i := y*dst.Stride + 4*x
+ pix[i+0] = uint8((sr * ma / 0xffff) >> 8)
+ pix[i+1] = uint8((sg * ma / 0xffff) >> 8)
+ pix[i+2] = uint8((sb * ma / 0xffff) >> 8)
+ pix[i+3] = uint8((sa * ma / 0xffff) >> 8)
+ }
+ }
+}
+
+func (z *Rasterizer) rasterizeOpOver(dst draw.Image, r image.Rectangle, src image.Image, sp image.Point) {
+ z.accumulateMask()
+ out := color.RGBA64{}
+ outc := color.Color(&out)
+ for y, y1 := 0, r.Max.Y-r.Min.Y; y < y1; y++ {
+ for x, x1 := 0, r.Max.X-r.Min.X; x < x1; x++ {
+ sr, sg, sb, sa := src.At(sp.X+x, sp.Y+y).RGBA()
+ ma := z.bufU32[y*z.size.X+x]
+
+ // This algorithm comes from the standard library's image/draw
+ // package.
+ dr, dg, db, da := dst.At(r.Min.X+x, r.Min.Y+y).RGBA()
+ a := 0xffff - (sa * ma / 0xffff)
+ out.R = uint16((dr*a + sr*ma) / 0xffff)
+ out.G = uint16((dg*a + sg*ma) / 0xffff)
+ out.B = uint16((db*a + sb*ma) / 0xffff)
+ out.A = uint16((da*a + sa*ma) / 0xffff)
+
+ dst.Set(r.Min.X+x, r.Min.Y+y, outc)
+ }
+ }
+}
+
+func (z *Rasterizer) rasterizeOpSrc(dst draw.Image, r image.Rectangle, src image.Image, sp image.Point) {
+ z.accumulateMask()
+ out := color.RGBA64{}
+ outc := color.Color(&out)
+ for y, y1 := 0, r.Max.Y-r.Min.Y; y < y1; y++ {
+ for x, x1 := 0, r.Max.X-r.Min.X; x < x1; x++ {
+ sr, sg, sb, sa := src.At(sp.X+x, sp.Y+y).RGBA()
+ ma := z.bufU32[y*z.size.X+x]
+
+ // This algorithm comes from the standard library's image/draw
+ // package.
+ out.R = uint16(sr * ma / 0xffff)
+ out.G = uint16(sg * ma / 0xffff)
+ out.B = uint16(sb * ma / 0xffff)
+ out.A = uint16(sa * ma / 0xffff)
+
+ dst.Set(r.Min.X+x, r.Min.Y+y, outc)
+ }
+ }
+}