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path.go
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path.go
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package svg
import (
"github.com/cdillond/gdf"
)
type pdfPathCmd struct {
op pdfPathOp
args []gdf.Point
}
type pdfPathOp uint
const (
moveTo pdfPathOp = iota
lineTo
curveTo
closePath
circle
ellipse
rect
arc
badpathOp
)
func (p pdfPathOp) isValid() bool {
return p < badpathOp
}
func svgPathOp2pdfPathOp(p svgPathOp) pdfPathOp {
switch p {
case mAbs, mRel:
return moveTo
case lAbs, lRel, hAbs, hRel, vAbs, vRel:
return lineTo
case zAbs, zRel:
return closePath
case cAbs, cRel, sAbs, sRel, qAbs, qRel, tAbs, tRel:
return curveTo
case aAbs, aRel:
return arc
}
return badpathOp
}
// Converts a Quadratic Bezier Curve to a Cubic Bezier Curve.
func quadraticToCubic(start, P1, dst gdf.Point) [4]gdf.Point {
// https://fontforge.org/docs/techref/bezier.html#converting-truetype-to-postscript
var out [4]gdf.Point
out[0] = start
out[3] = dst
// control point 1
out[1].X = 2. / 3. * (P1.X - start.X)
out[1].Y = 2. / 3. * (P1.Y - start.Y)
out[1].X += P1.X
out[1].Y += P1.Y
// control point 2
out[2].X = 2. / 3. * (P1.X - dst.X)
out[2].Y = 2. / 3. * (P1.Y - dst.Y)
out[2].X += dst.X
out[2].Y += dst.Y
return out
}
func resolvePathCmds(data []svgCmd) []pdfPathCmd {
var cur gdf.Point
var ctrlPt gdf.Point
var out []pdfPathCmd
for _, rcmd := range data {
switch rcmd.op {
case zAbs, zRel:
out = append(out, pdfPathCmd{op: svgPathOp2pdfPathOp(rcmd.op)})
case hAbs, hRel, vAbs, vRel:
switch rcmd.op {
case hAbs:
cur.X = rcmd.args[0]
case hRel:
cur.X += rcmd.args[0]
case vAbs:
cur.Y = rcmd.args[0]
case vRel:
cur.Y += rcmd.args[0]
}
out = append(out, pdfPathCmd{
op: svgPathOp2pdfPathOp(rcmd.op),
args: []gdf.Point{cur},
})
case mAbs, lAbs, mRel, lRel:
for n := 0; n < len(rcmd.args); n += 2 {
switch rcmd.op {
case mAbs, lAbs:
cur = gdf.Point{X: rcmd.args[n+0], Y: rcmd.args[n+1]}
if n > 0 {
rcmd.op = lAbs
}
case mRel, lRel:
cur.X += rcmd.args[n+0]
cur.Y += rcmd.args[n+1]
if n > 0 {
rcmd.op = lRel
}
}
out = append(out, pdfPathCmd{
op: svgPathOp2pdfPathOp(rcmd.op),
args: []gdf.Point{cur},
})
}
case cAbs, cRel, sAbs, sRel:
for n := 0; n < len(rcmd.args); n += 6 {
var pts []gdf.Point
if ctrlPt.X == 0 && ctrlPt.Y == 0 {
ctrlPt = cur
}
switch rcmd.op {
case sAbs:
ctrlPt.X = cur.X + (cur.X - ctrlPt.X)
ctrlPt.Y = cur.Y + (cur.Y - ctrlPt.Y)
pts = []gdf.Point{
ctrlPt,
{X: rcmd.args[n+0], Y: rcmd.args[n+1]},
{X: rcmd.args[n+2], Y: rcmd.args[n+3]},
}
ctrlPt = gdf.Point{X: rcmd.args[n+0], Y: rcmd.args[n+1]}
cur = gdf.Point{X: rcmd.args[n+2], Y: rcmd.args[n+3]}
case sRel:
ctrlPt.X = cur.X + (cur.X - ctrlPt.X)
ctrlPt.Y = cur.Y + (cur.Y - ctrlPt.Y)
pts = []gdf.Point{
ctrlPt,
{X: cur.X + rcmd.args[n+0], Y: cur.Y + rcmd.args[n+1]},
{X: cur.X + rcmd.args[n+2], Y: cur.Y + rcmd.args[n+3]},
}
ctrlPt = gdf.Point{X: cur.X + rcmd.args[n+0], Y: cur.Y + rcmd.args[n+1]}
cur = gdf.Point{X: cur.X + rcmd.args[n+2], Y: cur.Y + rcmd.args[n+3]}
case cAbs:
pts = []gdf.Point{
{X: rcmd.args[n+0], Y: rcmd.args[n+1]},
{X: rcmd.args[n+2], Y: rcmd.args[n+3]},
{X: rcmd.args[n+4], Y: rcmd.args[n+5]},
}
ctrlPt = gdf.Point{X: rcmd.args[n+2], Y: rcmd.args[n+3]}
cur = gdf.Point{X: rcmd.args[n+4], Y: rcmd.args[n+5]}
case cRel:
pts = []gdf.Point{
{X: cur.X + rcmd.args[n+0], Y: cur.Y + rcmd.args[n+1]},
{X: cur.X + rcmd.args[n+2], Y: cur.Y + rcmd.args[n+3]},
{X: cur.X + rcmd.args[n+4], Y: cur.Y + rcmd.args[n+5]},
}
ctrlPt = gdf.Point{X: cur.X + rcmd.args[n+2], Y: cur.Y + rcmd.args[n+3]}
cur = gdf.Point{X: cur.X + rcmd.args[n+4], Y: cur.Y + rcmd.args[n+5]}
}
out = append(out, pdfPathCmd{
op: svgPathOp2pdfPathOp(rcmd.op),
args: pts,
})
}
case tAbs, tRel, qAbs, qRel:
var endPt gdf.Point
switch rcmd.op {
case tAbs:
ctrlPt.X += (cur.X - ctrlPt.X)
ctrlPt.Y += (cur.Y - ctrlPt.Y)
endPt.X = rcmd.args[0]
endPt.Y = rcmd.args[1]
case tRel:
ctrlPt.X += (cur.X - ctrlPt.X)
ctrlPt.Y += (cur.Y - ctrlPt.Y)
endPt.X = cur.X + rcmd.args[0]
endPt.Y = cur.Y + rcmd.args[1]
case qAbs:
ctrlPt.X = rcmd.args[0]
ctrlPt.Y = rcmd.args[1]
endPt.X = rcmd.args[2]
endPt.Y = rcmd.args[3]
case qRel:
ctrlPt.X = cur.X + rcmd.args[0]
ctrlPt.Y = cur.Y + rcmd.args[1]
endPt.X = cur.X + rcmd.args[2]
endPt.Y = cur.Y + rcmd.args[3]
}
cubic := quadraticToCubic(cur, ctrlPt, endPt)
cur = endPt
out = append(out, pdfPathCmd{
op: svgPathOp2pdfPathOp(rcmd.op),
args: cubic[:],
})
case aRel:
ep := endParams{
cur.X, cur.Y,
rcmd.args[0],
rcmd.args[1],
gdf.Deg * rcmd.args[2],
rcmd.args[3],
rcmd.args[4],
cur.X + rcmd.args[5],
cur.Y + rcmd.args[6],
}
cur.X += rcmd.args[5]
cur.Y += rcmd.args[6]
c := center(ep)
out = append(out, pdfPathCmd{
op: svgPathOp2pdfPathOp(rcmd.op),
args: []gdf.Point{
{c.cx, c.cy},
{c.rx, c.ry},
{c.theta, c.delta},
{X: c.phi},
},
},
)
case aAbs:
ep := endParams{
x1: cur.X, y1: cur.Y,
rx: rcmd.args[0],
ry: rcmd.args[1],
phi: gdf.Deg * rcmd.args[2],
largeFlag: rcmd.args[3],
sweepFlag: rcmd.args[4],
x2: rcmd.args[5],
y2: rcmd.args[6],
}
cur.X = rcmd.args[5]
cur.Y = rcmd.args[6]
c := center(ep)
out = append(out, pdfPathCmd{
op: svgPathOp2pdfPathOp(rcmd.op),
args: []gdf.Point{
{c.cx, c.cy},
{c.rx, c.ry},
{c.theta, c.delta},
{X: c.phi},
},
},
)
}
}
return out
}