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Diffstat (limited to 'vendor/golang.org/x/image/vector/raster_floating.go')
-rw-r--r--vendor/golang.org/x/image/vector/raster_floating.go220
1 files changed, 0 insertions, 220 deletions
diff --git a/vendor/golang.org/x/image/vector/raster_floating.go b/vendor/golang.org/x/image/vector/raster_floating.go
deleted file mode 100644
index fd11db1..0000000
--- a/vendor/golang.org/x/image/vector/raster_floating.go
+++ /dev/null
@@ -1,220 +0,0 @@
-// 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
-
-// This file contains a floating point math implementation of the vector
-// graphics rasterizer.
-
-import (
- "math"
-)
-
-func floatingMax(x, y float32) float32 {
- if x > y {
- return x
- }
- return y
-}
-
-func floatingMin(x, y float32) float32 {
- if x < y {
- return x
- }
- return y
-}
-
-func floatingFloor(x float32) int32 { return int32(math.Floor(float64(x))) }
-func floatingCeil(x float32) int32 { return int32(math.Ceil(float64(x))) }
-
-func (z *Rasterizer) floatingLineTo(bx, by float32) {
- ax, ay := z.penX, z.penY
- z.penX, z.penY = bx, by
- dir := float32(1)
- if ay > by {
- dir, ax, ay, bx, by = -1, bx, by, ax, ay
- }
- // Horizontal line segments yield no change in coverage. Almost horizontal
- // segments would yield some change, in ideal math, but the computation
- // further below, involving 1 / (by - ay), is unstable in floating point
- // math, so we treat the segment as if it was perfectly horizontal.
- if by-ay <= 0.000001 {
- return
- }
- dxdy := (bx - ax) / (by - ay)
-
- x := ax
- y := floatingFloor(ay)
- yMax := floatingCeil(by)
- if yMax > int32(z.size.Y) {
- yMax = int32(z.size.Y)
- }
- width := int32(z.size.X)
-
- for ; y < yMax; y++ {
- dy := floatingMin(float32(y+1), by) - floatingMax(float32(y), ay)
-
- // The "float32" in expressions like "float32(foo*bar)" here and below
- // look redundant, since foo and bar already have type float32, but are
- // explicit in order to disable the compiler's Fused Multiply Add (FMA)
- // instruction selection, which can improve performance but can result
- // in different rounding errors in floating point computations.
- //
- // This package aims to have bit-exact identical results across all
- // GOARCHes, and across pure Go code and assembly, so it disables FMA.
- //
- // See the discussion at
- // https://groups.google.com/d/topic/golang-dev/Sti0bl2xUXQ/discussion
- xNext := x + float32(dy*dxdy)
- if y < 0 {
- x = xNext
- continue
- }
- buf := z.bufF32[y*width:]
- d := float32(dy * dir)
- x0, x1 := x, xNext
- if x > xNext {
- x0, x1 = x1, x0
- }
- x0i := floatingFloor(x0)
- x0Floor := float32(x0i)
- x1i := floatingCeil(x1)
- x1Ceil := float32(x1i)
-
- if x1i <= x0i+1 {
- xmf := float32(0.5*(x+xNext)) - x0Floor
- if i := clamp(x0i+0, width); i < uint(len(buf)) {
- buf[i] += d - float32(d*xmf)
- }
- if i := clamp(x0i+1, width); i < uint(len(buf)) {
- buf[i] += float32(d * xmf)
- }
- } else {
- s := 1 / (x1 - x0)
- x0f := x0 - x0Floor
- oneMinusX0f := 1 - x0f
- a0 := float32(0.5 * s * oneMinusX0f * oneMinusX0f)
- x1f := x1 - x1Ceil + 1
- am := float32(0.5 * s * x1f * x1f)
-
- if i := clamp(x0i, width); i < uint(len(buf)) {
- buf[i] += float32(d * a0)
- }
-
- if x1i == x0i+2 {
- if i := clamp(x0i+1, width); i < uint(len(buf)) {
- buf[i] += float32(d * (1 - a0 - am))
- }
- } else {
- a1 := float32(s * (1.5 - x0f))
- if i := clamp(x0i+1, width); i < uint(len(buf)) {
- buf[i] += float32(d * (a1 - a0))
- }
- dTimesS := float32(d * s)
- for xi := x0i + 2; xi < x1i-1; xi++ {
- if i := clamp(xi, width); i < uint(len(buf)) {
- buf[i] += dTimesS
- }
- }
- a2 := a1 + float32(s*float32(x1i-x0i-3))
- if i := clamp(x1i-1, width); i < uint(len(buf)) {
- buf[i] += float32(d * (1 - a2 - am))
- }
- }
-
- if i := clamp(x1i, width); i < uint(len(buf)) {
- buf[i] += float32(d * am)
- }
- }
-
- x = xNext
- }
-}
-
-const (
- // almost256 scales a floating point value in the range [0, 1] to a uint8
- // value in the range [0x00, 0xff].
- //
- // 255 is too small. Floating point math accumulates rounding errors, so a
- // fully covered src value that would in ideal math be float32(1) might be
- // float32(1-ε), and uint8(255 * (1-ε)) would be 0xfe instead of 0xff. The
- // uint8 conversion rounds to zero, not to nearest.
- //
- // 256 is too big. If we multiplied by 256, below, then a fully covered src
- // value of float32(1) would translate to uint8(256 * 1), which can be 0x00
- // instead of the maximal value 0xff.
- //
- // math.Float32bits(almost256) is 0x437fffff.
- almost256 = 255.99998
-
- // almost65536 scales a floating point value in the range [0, 1] to a
- // uint16 value in the range [0x0000, 0xffff].
- //
- // math.Float32bits(almost65536) is 0x477fffff.
- almost65536 = almost256 * 256
-)
-
-func floatingAccumulateOpOver(dst []uint8, src []float32) {
- // Sanity check that len(dst) >= len(src).
- if len(dst) < len(src) {
- return
- }
-
- acc := float32(0)
- for i, v := range src {
- acc += v
- a := acc
- if a < 0 {
- a = -a
- }
- if a > 1 {
- a = 1
- }
- // This algorithm comes from the standard library's image/draw package.
- dstA := uint32(dst[i]) * 0x101
- maskA := uint32(almost65536 * a)
- outA := dstA*(0xffff-maskA)/0xffff + maskA
- dst[i] = uint8(outA >> 8)
- }
-}
-
-func floatingAccumulateOpSrc(dst []uint8, src []float32) {
- // Sanity check that len(dst) >= len(src).
- if len(dst) < len(src) {
- return
- }
-
- acc := float32(0)
- for i, v := range src {
- acc += v
- a := acc
- if a < 0 {
- a = -a
- }
- if a > 1 {
- a = 1
- }
- dst[i] = uint8(almost256 * a)
- }
-}
-
-func floatingAccumulateMask(dst []uint32, src []float32) {
- // Sanity check that len(dst) >= len(src).
- if len(dst) < len(src) {
- return
- }
-
- acc := float32(0)
- for i, v := range src {
- acc += v
- a := acc
- if a < 0 {
- a = -a
- }
- if a > 1 {
- a = 1
- }
- dst[i] = uint32(almost65536 * a)
- }
-}