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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.
package iconvg
import (
"errors"
"image/color"
"math"
"golang.org/x/image/math/f32"
)
var (
errCSELUsedAsBothGradientAndStop = errors.New("iconvg: CSEL used as both gradient and stop")
errDrawingOpsUsedInStylingMode = errors.New("iconvg: drawing ops used in styling mode")
errInvalidSelectorAdjustment = errors.New("iconvg: invalid selector adjustment")
errInvalidIncrementingAdjustment = errors.New("iconvg: invalid incrementing adjustment")
errStylingOpsUsedInDrawingMode = errors.New("iconvg: styling ops used in drawing mode")
errTooManyGradientStops = errors.New("iconvg: too many gradient stops")
)
type mode uint8
const (
modeInitial mode = iota
modeStyling
modeDrawing
)
// Encoder is an IconVG encoder.
//
// The zero value is usable. Calling Reset, which is optional, sets the
// Metadata for the subsequent encoded form. If Reset is not called before
// other Encoder methods, the default metadata is implied.
type Encoder struct {
// HighResolutionCoordinates is whether the encoder should encode
// coordinate numbers for subsequent paths at the best possible resolution
// afforded by the underlying graphic format.
//
// By default (false), the encoder quantizes coordinates to 1/64th of a
// unit if possible (the default graphic size is 64 by 64 units, so
// 1/4096th of the default width or height). Each such coordinate can
// therefore be encoded in either 1 or 2 bytes. If true, some coordinates
// will be encoded in 4 bytes, giving greater accuracy but larger file
// sizes. On the Material Design icon set, the 950 or so icons take up
// around 40% more bytes (172K vs 123K) at high resolution.
//
// See the package documentation for more details on the coordinate number
// encoding format.
HighResolutionCoordinates bool
// highResolutionCoordinates is a local copy, copied during StartPath, to
// avoid having to specify the semantics of modifying the exported field
// while drawing.
highResolutionCoordinates bool
buf buffer
altBuf buffer
metadata Metadata
err error
lod0 float32
lod1 float32
cSel uint8
nSel uint8
mode mode
drawOp byte
drawArgs []float32
scratch [12]byte
}
// Bytes returns the encoded form.
func (e *Encoder) Bytes() ([]byte, error) {
if e.err != nil {
return nil, e.err
}
if e.mode == modeInitial {
e.appendDefaultMetadata()
}
return []byte(e.buf), nil
}
// Reset resets the Encoder for the given Metadata.
//
// This includes setting e.HighResolutionCoordinates to false.
func (e *Encoder) Reset(m Metadata) {
*e = Encoder{
buf: append(e.buf[:0], magic...),
metadata: m,
mode: modeStyling,
lod1: positiveInfinity,
}
nMetadataChunks := 0
mcViewBox := m.ViewBox != DefaultViewBox
if mcViewBox {
nMetadataChunks++
}
mcSuggestedPalette := m.Palette != DefaultPalette
if mcSuggestedPalette {
nMetadataChunks++
}
e.buf.encodeNatural(uint32(nMetadataChunks))
if mcViewBox {
e.altBuf = e.altBuf[:0]
e.altBuf.encodeNatural(midViewBox)
e.altBuf.encodeCoordinate(m.ViewBox.Min[0])
e.altBuf.encodeCoordinate(m.ViewBox.Min[1])
e.altBuf.encodeCoordinate(m.ViewBox.Max[0])
e.altBuf.encodeCoordinate(m.ViewBox.Max[1])
e.buf.encodeNatural(uint32(len(e.altBuf)))
e.buf = append(e.buf, e.altBuf...)
}
if mcSuggestedPalette {
n := 63
for ; n >= 0 && m.Palette[n] == (color.RGBA{0x00, 0x00, 0x00, 0xff}); n-- {
}
// Find the shortest encoding that can represent all of m.Palette's n+1
// explicit colors.
enc1, enc2, enc3 := true, true, true
for _, c := range m.Palette[:n+1] {
if enc1 && (!is1(c.R) || !is1(c.G) || !is1(c.B) || !is1(c.A)) {
enc1 = false
}
if enc2 && (!is2(c.R) || !is2(c.G) || !is2(c.B) || !is2(c.A)) {
enc2 = false
}
if enc3 && (c.A != 0xff) {
enc3 = false
}
}
e.altBuf = e.altBuf[:0]
e.altBuf.encodeNatural(midSuggestedPalette)
if enc1 {
e.altBuf = append(e.altBuf, byte(n)|0x00)
for _, c := range m.Palette[:n+1] {
x, _ := encodeColor1(RGBAColor(c))
e.altBuf = append(e.altBuf, x)
}
} else if enc2 {
e.altBuf = append(e.altBuf, byte(n)|0x40)
for _, c := range m.Palette[:n+1] {
x, _ := encodeColor2(RGBAColor(c))
e.altBuf = append(e.altBuf, x[0], x[1])
}
} else if enc3 {
e.altBuf = append(e.altBuf, byte(n)|0x80)
for _, c := range m.Palette[:n+1] {
e.altBuf = append(e.altBuf, c.R, c.G, c.B)
}
} else {
e.altBuf = append(e.altBuf, byte(n)|0xc0)
for _, c := range m.Palette[:n+1] {
e.altBuf = append(e.altBuf, c.R, c.G, c.B, c.A)
}
}
e.buf.encodeNatural(uint32(len(e.altBuf)))
e.buf = append(e.buf, e.altBuf...)
}
}
func (e *Encoder) appendDefaultMetadata() {
e.buf = append(e.buf[:0], magic...)
e.buf = append(e.buf, 0x00) // There are zero metadata chunks.
e.mode = modeStyling
}
func (e *Encoder) CSel() uint8 {
if e.mode == modeInitial {
e.appendDefaultMetadata()
}
return e.cSel
}
func (e *Encoder) NSel() uint8 {
if e.mode == modeInitial {
e.appendDefaultMetadata()
}
return e.nSel
}
func (e *Encoder) LOD() (lod0, lod1 float32) {
if e.mode == modeInitial {
e.appendDefaultMetadata()
}
return e.lod0, e.lod1
}
func (e *Encoder) checkModeStyling() {
if e.mode == modeStyling {
return
}
if e.mode == modeInitial {
e.appendDefaultMetadata()
return
}
e.err = errStylingOpsUsedInDrawingMode
}
func (e *Encoder) SetCSel(cSel uint8) {
e.checkModeStyling()
if e.err != nil {
return
}
e.cSel = cSel & 0x3f
e.buf = append(e.buf, e.cSel)
}
func (e *Encoder) SetNSel(nSel uint8) {
e.checkModeStyling()
if e.err != nil {
return
}
e.nSel = nSel & 0x3f
e.buf = append(e.buf, e.nSel|0x40)
}
func (e *Encoder) SetCReg(adj uint8, incr bool, c Color) {
e.checkModeStyling()
if e.err != nil {
return
}
if adj < 0 || 6 < adj {
e.err = errInvalidSelectorAdjustment
return
}
if incr {
if adj != 0 {
e.err = errInvalidIncrementingAdjustment
}
adj = 7
}
if x, ok := encodeColor1(c); ok {
e.buf = append(e.buf, adj|0x80, x)
return
}
if x, ok := encodeColor2(c); ok {
e.buf = append(e.buf, adj|0x88, x[0], x[1])
return
}
if x, ok := encodeColor3Direct(c); ok {
e.buf = append(e.buf, adj|0x90, x[0], x[1], x[2])
return
}
if x, ok := encodeColor4(c); ok {
e.buf = append(e.buf, adj|0x98, x[0], x[1], x[2], x[3])
return
}
if x, ok := encodeColor3Indirect(c); ok {
e.buf = append(e.buf, adj|0xa0, x[0], x[1], x[2])
return
}
panic("unreachable")
}
func (e *Encoder) SetNReg(adj uint8, incr bool, f float32) {
e.checkModeStyling()
if e.err != nil {
return
}
if adj < 0 || 6 < adj {
e.err = errInvalidSelectorAdjustment
return
}
if incr {
if adj != 0 {
e.err = errInvalidIncrementingAdjustment
}
adj = 7
}
// Try three different encodings and pick the shortest.
b := buffer(e.scratch[0:0])
opcode, iBest, nBest := uint8(0xa8), 0, b.encodeReal(f)
b = buffer(e.scratch[4:4])
if n := b.encodeCoordinate(f); n < nBest {
opcode, iBest, nBest = 0xb0, 4, n
}
b = buffer(e.scratch[8:8])
if n := b.encodeZeroToOne(f); n < nBest {
opcode, iBest, nBest = 0xb8, 8, n
}
e.buf = append(e.buf, adj|opcode)
e.buf = append(e.buf, e.scratch[iBest:iBest+nBest]...)
}
func (e *Encoder) SetLOD(lod0, lod1 float32) {
e.checkModeStyling()
if e.err != nil {
return
}
e.lod0 = lod0
e.lod1 = lod1
e.buf = append(e.buf, 0xc7)
e.buf.encodeReal(lod0)
e.buf.encodeReal(lod1)
}
// SetGradient sets CREG[CSEL] to encode the gradient whose colors defined by
// spread and stops. Its geometry is either linear or radial, depending on the
// radial argument, and the given affine transformation matrix maps from
// graphic coordinate space defined by the metadata's viewBox (e.g. from (-32,
// -32) to (+32, +32)) to gradient coordinate space. Gradient coordinate space
// is where a linear gradient ranges from x=0 to x=1, and a radial gradient has
// center (0, 0) and radius 1.
//
// The colors of the n stops are encoded at CREG[cBase+0], CREG[cBase+1], ...,
// CREG[cBase+n-1]. Similarly, the offsets of the n stops are encoded at
// NREG[nBase+0], NREG[nBase+1], ..., NREG[nBase+n-1]. Additional parameters
// are stored at NREG[nBase-4], NREG[nBase-3], NREG[nBase-2] and NREG[nBase-1].
//
// The CSEL and NSEL selector registers maintain the same values after the
// method returns as they had when the method was called.
//
// See the package documentation for more details on the gradient encoding
// format and the derivation of common transformation matrices.
func (e *Encoder) SetGradient(cBase, nBase uint8, radial bool, transform f32.Aff3, spread GradientSpread, stops []GradientStop) {
e.checkModeStyling()
if e.err != nil {
return
}
if len(stops) > 64-len(transform) {
e.err = errTooManyGradientStops
return
}
if x, y := e.cSel, e.cSel+64; (cBase <= x && x < cBase+uint8(len(stops))) ||
(cBase <= y && y < cBase+uint8(len(stops))) {
e.err = errCSELUsedAsBothGradientAndStop
return
}
oldCSel := e.cSel
oldNSel := e.nSel
cBase &= 0x3f
nBase &= 0x3f
bFlags := uint8(0x80)
if radial {
bFlags = 0xc0
}
e.SetCReg(0, false, RGBAColor(color.RGBA{
R: uint8(len(stops)),
G: cBase | uint8(spread<<6),
B: nBase | bFlags,
A: 0x00,
}))
e.SetCSel(cBase)
e.SetNSel(nBase)
for i, v := range transform {
e.SetNReg(uint8(len(transform)-i), false, v)
}
for _, s := range stops {
r, g, b, a := s.Color.RGBA()
e.SetCReg(0, true, RGBAColor(color.RGBA{
R: uint8(r >> 8),
G: uint8(g >> 8),
B: uint8(b >> 8),
A: uint8(a >> 8),
}))
e.SetNReg(0, true, s.Offset)
}
e.SetCSel(oldCSel)
e.SetNSel(oldNSel)
}
// SetLinearGradient is like SetGradient with radial=false except that the
// transformation matrix is implicitly defined by two boundary points (x1, y1)
// and (x2, y2).
func (e *Encoder) SetLinearGradient(cBase, nBase uint8, x1, y1, x2, y2 float32, spread GradientSpread, stops []GradientStop) {
// See the package documentation's appendix for a derivation of the
// transformation matrix.
dx, dy := x2-x1, y2-y1
d := dx*dx + dy*dy
ma := dx / d
mb := dy / d
e.SetGradient(cBase, nBase, false, f32.Aff3{
ma, mb, -ma*x1 - mb*y1,
0, 0, 0,
}, spread, stops)
}
// SetCircularGradient is like SetGradient with radial=true except that the
// transformation matrix is implicitly defined by a center (cx, cy) and a
// radius vector (rx, ry) such that (cx+rx, cy+ry) is on the circle.
func (e *Encoder) SetCircularGradient(cBase, nBase uint8, cx, cy, rx, ry float32, spread GradientSpread, stops []GradientStop) {
// See the package documentation's appendix for a derivation of the
// transformation matrix.
invR := float32(1 / math.Sqrt(float64(rx*rx+ry*ry)))
e.SetGradient(cBase, nBase, true, f32.Aff3{
invR, 0, -cx * invR,
0, invR, -cy * invR,
}, spread, stops)
}
// SetEllipticalGradient is like SetGradient with radial=true except that the
// transformation matrix is implicitly defined by a center (cx, cy) and two
// axis vectors (rx, ry) and (sx, sy) such that (cx+rx, cy+ry) and (cx+sx,
// cy+sy) are on the ellipse.
func (e *Encoder) SetEllipticalGradient(cBase, nBase uint8, cx, cy, rx, ry, sx, sy float32, spread GradientSpread, stops []GradientStop) {
// See the package documentation's appendix for a derivation of the
// transformation matrix.
invRSSR := 1 / (rx*sy - sx*ry)
ma := +sy * invRSSR
mb := -sx * invRSSR
mc := -ma*cx - mb*cy
md := -ry * invRSSR
me := +rx * invRSSR
mf := -md*cx - me*cy
e.SetGradient(cBase, nBase, true, f32.Aff3{
ma, mb, mc,
md, me, mf,
}, spread, stops)
}
func (e *Encoder) StartPath(adj uint8, x, y float32) {
e.checkModeStyling()
if e.err != nil {
return
}
if adj < 0 || 6 < adj {
e.err = errInvalidSelectorAdjustment
return
}
e.highResolutionCoordinates = e.HighResolutionCoordinates
e.buf = append(e.buf, uint8(0xc0+adj))
e.buf.encodeCoordinate(e.quantize(x))
e.buf.encodeCoordinate(e.quantize(y))
e.mode = modeDrawing
}
func (e *Encoder) AbsHLineTo(x float32) { e.draw('H', x, 0, 0, 0, 0, 0) }
func (e *Encoder) RelHLineTo(x float32) { e.draw('h', x, 0, 0, 0, 0, 0) }
func (e *Encoder) AbsVLineTo(y float32) { e.draw('V', y, 0, 0, 0, 0, 0) }
func (e *Encoder) RelVLineTo(y float32) { e.draw('v', y, 0, 0, 0, 0, 0) }
func (e *Encoder) AbsLineTo(x, y float32) { e.draw('L', x, y, 0, 0, 0, 0) }
func (e *Encoder) RelLineTo(x, y float32) { e.draw('l', x, y, 0, 0, 0, 0) }
func (e *Encoder) AbsSmoothQuadTo(x, y float32) { e.draw('T', x, y, 0, 0, 0, 0) }
func (e *Encoder) RelSmoothQuadTo(x, y float32) { e.draw('t', x, y, 0, 0, 0, 0) }
func (e *Encoder) AbsQuadTo(x1, y1, x, y float32) { e.draw('Q', x1, y1, x, y, 0, 0) }
func (e *Encoder) RelQuadTo(x1, y1, x, y float32) { e.draw('q', x1, y1, x, y, 0, 0) }
func (e *Encoder) AbsSmoothCubeTo(x2, y2, x, y float32) { e.draw('S', x2, y2, x, y, 0, 0) }
func (e *Encoder) RelSmoothCubeTo(x2, y2, x, y float32) { e.draw('s', x2, y2, x, y, 0, 0) }
func (e *Encoder) AbsCubeTo(x1, y1, x2, y2, x, y float32) { e.draw('C', x1, y1, x2, y2, x, y) }
func (e *Encoder) RelCubeTo(x1, y1, x2, y2, x, y float32) { e.draw('c', x1, y1, x2, y2, x, y) }
func (e *Encoder) ClosePathEndPath() { e.draw('Z', 0, 0, 0, 0, 0, 0) }
func (e *Encoder) ClosePathAbsMoveTo(x, y float32) { e.draw('Y', x, y, 0, 0, 0, 0) }
func (e *Encoder) ClosePathRelMoveTo(x, y float32) { e.draw('y', x, y, 0, 0, 0, 0) }
func (e *Encoder) AbsArcTo(rx, ry, xAxisRotation float32, largeArc, sweep bool, x, y float32) {
e.arcTo('A', rx, ry, xAxisRotation, largeArc, sweep, x, y)
}
func (e *Encoder) RelArcTo(rx, ry, xAxisRotation float32, largeArc, sweep bool, x, y float32) {
e.arcTo('a', rx, ry, xAxisRotation, largeArc, sweep, x, y)
}
func (e *Encoder) arcTo(drawOp byte, rx, ry, xAxisRotation float32, largeArc, sweep bool, x, y float32) {
flags := uint32(0)
if largeArc {
flags |= 0x01
}
if sweep {
flags |= 0x02
}
e.draw(drawOp, rx, ry, xAxisRotation, float32(flags), x, y)
}
func (e *Encoder) draw(drawOp byte, arg0, arg1, arg2, arg3, arg4, arg5 float32) {
if e.err != nil {
return
}
if e.mode != modeDrawing {
e.err = errDrawingOpsUsedInStylingMode
return
}
if e.drawOp != drawOp {
e.flushDrawOps()
}
e.drawOp = drawOp
switch drawOps[drawOp].nArgs {
case 0:
// No-op.
case 1:
e.drawArgs = append(e.drawArgs, arg0)
case 2:
e.drawArgs = append(e.drawArgs, arg0, arg1)
case 4:
e.drawArgs = append(e.drawArgs, arg0, arg1, arg2, arg3)
case 6:
e.drawArgs = append(e.drawArgs, arg0, arg1, arg2, arg3, arg4, arg5)
default:
panic("unreachable")
}
switch drawOp {
case 'Z':
e.mode = modeStyling
fallthrough
case 'Y', 'y':
e.flushDrawOps()
}
}
func (e *Encoder) flushDrawOps() {
if e.drawOp == 0x00 {
return
}
if op := drawOps[e.drawOp]; op.nArgs == 0 {
e.buf = append(e.buf, op.opcodeBase)
} else {
n := len(e.drawArgs) / int(op.nArgs)
for i := 0; n > 0; {
m := n
if m > int(op.maxRepCount) {
m = int(op.maxRepCount)
}
e.buf = append(e.buf, op.opcodeBase+uint8(m)-1)
switch e.drawOp {
default:
for j := m * int(op.nArgs); j > 0; j-- {
e.buf.encodeCoordinate(e.quantize(e.drawArgs[i]))
i++
}
case 'A', 'a':
for j := m; j > 0; j-- {
e.buf.encodeCoordinate(e.quantize(e.drawArgs[i+0]))
e.buf.encodeCoordinate(e.quantize(e.drawArgs[i+1]))
e.buf.encodeAngle(e.drawArgs[i+2])
e.buf.encodeNatural(uint32(e.drawArgs[i+3]))
e.buf.encodeCoordinate(e.quantize(e.drawArgs[i+4]))
e.buf.encodeCoordinate(e.quantize(e.drawArgs[i+5]))
i += 6
}
}
n -= m
}
}
e.drawOp = 0x00
e.drawArgs = e.drawArgs[:0]
}
func (e *Encoder) quantize(coord float32) float32 {
if !e.highResolutionCoordinates && (-128 <= coord && coord < 128) {
x := math.Floor(float64(coord*64 + 0.5))
return float32(x) / 64
}
return coord
}
var drawOps = [256]struct {
opcodeBase byte
maxRepCount uint8
nArgs uint8
}{
'L': {0x00, 32, 2},
'l': {0x20, 32, 2},
'T': {0x40, 16, 2},
't': {0x50, 16, 2},
'Q': {0x60, 16, 4},
'q': {0x70, 16, 4},
'S': {0x80, 16, 4},
's': {0x90, 16, 4},
'C': {0xa0, 16, 6},
'c': {0xb0, 16, 6},
'A': {0xc0, 16, 6},
'a': {0xd0, 16, 6},
// Z means close path and then end path.
'Z': {0xe1, 1, 0},
// Y/y means close path and then open a new path (with a MoveTo/moveTo).
'Y': {0xe2, 1, 2},
'y': {0xe3, 1, 2},
'H': {0xe6, 1, 1},
'h': {0xe7, 1, 1},
'V': {0xe8, 1, 1},
'v': {0xe9, 1, 1},
}
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