gg/animation.go

package gg

import (
	"github.com/hajimehoshi/ebiten/v2"
	//"fmt"
)

type Animation []*Image

type AnimationDefine struct{
	Id AnimationId
	Indexes []ImageRectIndex
}
// Animation define
func AD(id AnimationId, indexes ...ImageRectIndex) AnimationDefine {
	return AnimationDefine{
		Id: id,
		Indexes: indexes,
	}
}
func (ad AnimationDefine) DefRow(y int, xs ...int) AnimationDefine {
	for _, x := range xs {
		ad.Indexes = append(ad.Indexes, ImageRectIndex{x, y})
	}
	return ad
}

func (ad AnimationDefine) DefCol(x int, ys ...int) AnimationDefine {
	for _, y := range ys {
		ad.Indexes = append(ad.Indexes, ImageRectIndex{x, y})
	}
	return ad
}

type AnimationId int
type AnimationSet map[AnimationId] Animation
func AnimationSetFromImage(
	img *Image,
	w, h int,
	defines ...AnimationDefine,
) (AnimationSet, error) {
	set := AnimationSet{}

	r := img.Bounds()
	fw, fh := r.Dx()/w, r.Dy()/h

	for _, define := range defines {
		animation := make(Animation, len(define.Indexes))
		for i := range animation {
			idx := define.Indexes[i]
			animation[i] = ebiten.NewImageFromImage(img.SubImage(
				ImageRect{
					Min: ImagePoint{idx.X*fw, idx.Y*fh},
					Max: ImagePoint{(idx.X+1)*fw, (idx.Y+1)*fh},
				},
			))
		}
		set[define.Id] = animation
	}

	return set, nil
}

// The type implements animated sprites.
type AnimatedSprite struct {
	Sprite
	Animations AnimationSet
	AnimationId AnimationId
	CurrentFrame int
	// This is time between animation frames, not
	// engine ones.
	TimeBetweenFrames Duration
	duration Duration
}

func (as *AnimatedSprite) Animate(id AnimationId) bool {
	if as.AnimationId == id {
		return true
	}
	_, ok := as.Animations[id]
	if ok {
		as.duration = 0
		as.AnimationId = id
	}
	return ok
}

func (as *AnimatedSprite) Draw(c *Context) []EVertex {
	as.duration += c.DrawDt()
	frames := as.Animations[as.AnimationId]
	fullTime := Duration(len(frames)) * as.TimeBetweenFrames
	if as.duration > fullTime {
		as.duration -= fullTime
	}
	as.Images[0] = frames[(as.duration/as.TimeBetweenFrames)%Duration(len(frames))]

	return as.Sprite.Draw(c)
}