pobounty/reward.go

package main

import (
	"bytes"
	_ "embed"
	"image"
	_ "image/png"

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

const (
	REWARD_HEIGHT = 32
	REWARD_WIDTH  = 32

	REWARD_FX_CYCLES    = 9  //number of animation cycles for effects
	REWARD_FX_SHEEN_IDX = 11 //row offset from png, sheen effect
	REWARD_FX_SPRKL_IDX = 7  //row offset from png, sparkle effect
)

var (
	//go:embed resources/images/gold.png
	assetsReward_png []byte
	rewardsImage     *ebiten.Image

	//go:embed resources/images/shiny.png
	assetsShiny_png []byte
	shinyImage      *ebiten.Image
)

type Reward struct {
	Sprite  *ebiten.Image
	scratch *ebiten.Image
	cycle   int
}

func NewReward() *Reward {
	r := &Reward{
		cycle: 0,
	}
	r.Sprite = ebiten.NewImageFromImage(rewardsImage)
	r.scratch = ebiten.NewImageFromImage(rewardsImage)
	return r
}

func (r *Reward) Animate() {

	r.scratch.Clear()
	r.Sprite.Clear()

	r.scratch.DrawImage(rewardsImage.SubImage(image.Rect(0, 0, REWARD_WIDTH, REWARD_HEIGHT)).(*ebiten.Image), nil)

	//animate the effects
	if r.cycle < REWARD_FX_CYCLES {
		//add sheen
		op := &ebiten.DrawImageOptions{}
		op.Blend = ebiten.BlendSourceAtop

		sx := r.cycle * REWARD_WIDTH
		sy := REWARD_HEIGHT * REWARD_FX_SHEEN_IDX

		ex := sx + REWARD_WIDTH
		ey := sy + REWARD_HEIGHT

		r.scratch.DrawImage(shinyImage.SubImage(image.Rect(sx, sy, ex, ey)).(*ebiten.Image), op)

		//add sparkle: x postions are identical to sheen (same png sheet), just need to compute new y offsets
		spsy := REWARD_HEIGHT * REWARD_FX_SPRKL_IDX
		spey := spsy + REWARD_HEIGHT
		op.GeoM.Translate(REWARD_WIDTH/2, REWARD_HEIGHT/2)
		r.scratch.DrawImage(shinyImage.SubImage(image.Rect(sx, spsy, ex, spey)).(*ebiten.Image), nil)
	}

	r.Sprite.DrawImage(r.scratch, nil)
	r.CycleUpdate()
}

func (r *Reward) CycleUpdate() {
	r.cycle = (r.cycle + 1) % (REWARD_FX_CYCLES * 8)
}

func (r *Reward) Width() int {
	return REWARD_WIDTH
}

func (r *Reward) Height() int {
	return REWARD_HEIGHT
}

func init() {

	img, _, err := image.Decode(bytes.NewReader(assetsReward_png))
	if err != nil {
		DashLogger.Fatal(err)
	}
	rewardsImage = ebiten.NewImageFromImage(img)

	img, _, err = image.Decode(bytes.NewReader(assetsShiny_png))
	if err != nil {
		DashLogger.Fatal(err)
	}
	shinyImage = ebiten.NewImageFromImage(img)

}