ebiten/vector/path.go
2019-04-20 23:08:20 +09:00

221 lines
5.2 KiB
Go

// Copyright 2019 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package vector provides functions for vector graphics rendering.
//
// This package is under experiments and the API might be changed with breaking backward compatibility.
package vector
import (
"image/color"
"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/vector/internal/math"
)
var emptyImage *ebiten.Image
func init() {
const w, h = 16, 16
emptyImage, _ = ebiten.NewImage(w, h, ebiten.FilterDefault)
pix := make([]byte, 4*w*h)
for i := range pix {
pix[i] = 0xff
}
emptyImage.ReplacePixels(pix)
}
// Path represents a collection of paths.
type Path struct {
segs [][]math.Segment
cur math.Point
}
// MoveTo skips the current position of the path to the given position (x, y) without adding any strokes.
func (p *Path) MoveTo(x, y float32) {
p.cur = math.Point{x, y}
if len(p.segs) > 0 && len(p.segs[len(p.segs)-1]) == 0 {
return
}
p.segs = append(p.segs, []math.Segment{})
}
// LineTo adds a math.Segment to the path, which starts from the current position and ends to the given position (x, y).
//
// LineTo updates the current position to (x, y).
func (p *Path) LineTo(x, y float32) {
if len(p.segs) == 0 {
p.segs = append(p.segs, []math.Segment{})
}
p.segs[len(p.segs)-1] = append(p.segs[len(p.segs)-1], math.Segment{p.cur, math.Point{x, y}})
p.cur = math.Point{x, y}
}
func (p *Path) strokeVertices(lineWidth float32, clr color.Color) (vertices []ebiten.Vertex, indices []uint16) {
const miterLimit = 10
if len(p.segs) == 0 {
return nil, nil
}
r, g, b, a := clr.RGBA()
rf, gf, bf, af := float32(r)/0xffff, float32(g)/0xffff, float32(b)/0xffff, float32(a)/0xffff
for _, ss := range p.segs {
idx := uint16(len(vertices))
for i, s := range ss {
s0 := s.Translate(-lineWidth / 2)
s1 := s.Translate(lineWidth / 2)
if i == 0 {
v0 := s0.P0
v1 := s1.P0
vertices = append(vertices,
ebiten.Vertex{
DstX: v0.X,
DstY: v0.Y,
SrcX: v0.X,
SrcY: v0.Y,
ColorR: rf,
ColorG: gf,
ColorB: bf,
ColorA: af,
},
ebiten.Vertex{
DstX: v1.X,
DstY: v1.Y,
SrcX: v1.X,
SrcY: v1.Y,
ColorR: rf,
ColorG: gf,
ColorB: bf,
ColorA: af,
})
}
v2 := s0.P1
v3 := s1.P1
cut := false
if i != len(ss)-1 {
ns := ss[i+1]
nv2 := ns.Translate(-lineWidth / 2).IntersectionAsLines(s0)
nv3 := ns.Translate(lineWidth / 2).IntersectionAsLines(s1)
l := lineWidth / 2 * miterLimit
if (nv2.X-nv3.X)*(nv2.X-nv3.X)+(nv2.Y-nv3.Y)*(nv2.Y-nv3.Y) < l*l {
v2 = nv2
v3 = nv3
} else {
cut = true
}
}
if cut {
ns := ss[i+1]
s2 := ns.Translate(-lineWidth / 2)
s3 := ns.Translate(lineWidth / 2)
vertices = append(vertices,
ebiten.Vertex{
DstX: s0.P1.X,
DstY: s0.P1.Y,
SrcX: s0.P1.X,
SrcY: s0.P1.Y,
ColorR: rf,
ColorG: gf,
ColorB: bf,
ColorA: af,
},
ebiten.Vertex{
DstX: s1.P1.X,
DstY: s1.P1.Y,
SrcX: s1.P1.X,
SrcY: s1.P1.Y,
ColorR: rf,
ColorG: gf,
ColorB: bf,
ColorA: af,
},
ebiten.Vertex{
DstX: s2.P0.X,
DstY: s2.P0.Y,
SrcX: s2.P0.X,
SrcY: s2.P0.Y,
ColorR: rf,
ColorG: gf,
ColorB: bf,
ColorA: af,
},
ebiten.Vertex{
DstX: s3.P0.X,
DstY: s3.P0.Y,
SrcX: s3.P0.X,
SrcY: s3.P0.Y,
ColorR: rf,
ColorG: gf,
ColorB: bf,
ColorA: af,
})
indices = append(indices, idx, idx+1, idx+2, idx+1, idx+2, idx+3,
idx+2, idx+3, idx+4, idx+3, idx+4, idx+5)
idx += 4
} else {
vertices = append(vertices,
ebiten.Vertex{
DstX: v2.X,
DstY: v2.Y,
SrcX: v2.X,
SrcY: v2.Y,
ColorR: rf,
ColorG: gf,
ColorB: bf,
ColorA: af,
},
ebiten.Vertex{
DstX: v3.X,
DstY: v3.Y,
SrcX: v3.X,
SrcY: v3.Y,
ColorR: rf,
ColorG: gf,
ColorB: bf,
ColorA: af,
})
indices = append(indices, idx, idx+1, idx+2, idx+1, idx+2, idx+3)
idx += 2
}
}
}
return
}
// DrawPathOptions is the options specified at (*Path).Draw.
type DrawPathOptions struct {
LineWidth float32
StrokeColor color.Color
}
// Draw draws the path by rendering its stroke or filling.
func (p *Path) Draw(target *ebiten.Image, op *DrawPathOptions) {
if op == nil {
return
}
// TODO: Implement filling
if op.StrokeColor != nil {
vs, is := p.strokeVertices(op.LineWidth, op.StrokeColor)
op := &ebiten.DrawTrianglesOptions{}
op.Address = ebiten.AddressRepeat
target.DrawTriangles(vs, is, emptyImage, op)
}
}