path-example.go

package main

import (
	"image"
	"image/color"
	"log"

	"github.com/hajimehoshi/ebiten/v2"
	"github.com/hajimehoshi/ebiten/v2/vector"
)

var (
	emptyImage = ebiten.NewImage(3, 3)

	// emptySubImage is an internal sub image of emptyImage.
	// Use emptySubImage at DrawTriangles instead of emptyImage in order to avoid bleeding edges.
	emptySubImage = emptyImage.SubImage(image.Rect(1, 1, 2, 2)).(*ebiten.Image)
)

func init() {
	emptyImage.Fill(color.White)
}

const (
	screenWidth  = 640
	screenHeight = 480
	size = 100
)

type Game struct {
}

func (g *Game) Update() error {
	return nil
}

func (g *Game) Draw(screen *ebiten.Image) {
	containerImage := ebiten.NewImage(size, size)
	containerImage.Fill(color.White)

	var path vector.Path
	path.MoveTo(0, 0)
	path.LineTo(0, size - 1)
	path.LineTo(size - 1, size - 1)
	path.LineTo(size - 1, 0)

	triOp := &ebiten.DrawTrianglesOptions{
		FillRule: ebiten.EvenOdd,
	}
	vs, is := path.AppendVerticesAndIndicesForFilling(nil, nil)
	for i := range vs {
		vs[i].SrcX = 1
		vs[i].SrcY = 1
		vs[i].ColorR = 0xdb / float32(0xff)
		vs[i].ColorG = 0x56 / float32(0xff)
		vs[i].ColorB = 0x20 / float32(0xff)
	}
	containerImage.DrawTriangles(vs, is, emptySubImage, triOp)

	op := &ebiten.DrawImageOptions{}
	op.GeoM.Translate(50, 50)
	screen.DrawImage(containerImage, op)
}

func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
	return screenWidth, screenHeight
}

func main() {
	ebiten.SetWindowSize(screenWidth, screenHeight)
	ebiten.SetWindowTitle("Path Test")
	if err := ebiten.RunGame(&Game{}); err != nil {
		log.Fatal(err)
	}
}