ebiten/examples/sprites/main.go

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// Copyright 2015 Hajime Hoshi
//
// 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.
// +build example jsgo
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package main
import (
"bytes"
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"fmt"
"image"
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_ "image/png"
"log"
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"math"
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"math/rand"
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"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/ebitenutil"
"github.com/hajimehoshi/ebiten/examples/resources/images"
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)
const (
screenWidth = 320
screenHeight = 240
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maxAngle = 256
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)
var (
ebitenImage *ebiten.Image
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)
type Sprite struct {
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imageWidth int
imageHeight int
x int
y int
vx int
vy int
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angle int
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}
func (s *Sprite) Update() {
s.x += s.vx
s.y += s.vy
if s.x < 0 {
s.x = -s.x
s.vx = -s.vx
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} else if mx := screenWidth - s.imageWidth; mx <= s.x {
s.x = 2*mx - s.x
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s.vx = -s.vx
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}
if s.y < 0 {
s.y = -s.y
s.vy = -s.vy
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} else if my := screenHeight - s.imageHeight; my <= s.y {
s.y = 2*my - s.y
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s.vy = -s.vy
}
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s.angle++
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if s.angle == maxAngle {
s.angle = 0
}
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}
type Sprites struct {
sprites []*Sprite
num int
}
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func (s *Sprites) Update() {
for i := 0; i < s.num; i++ {
s.sprites[i].Update()
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}
}
const (
MinSprites = 0
MaxSprites = 50000
)
var (
sprites = &Sprites{make([]*Sprite, MaxSprites), 500}
op = &ebiten.DrawImageOptions{}
)
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func init() {
// Decode image from a byte slice instead of a file so that
// this example works in any working directory.
// If you want to use a file, there are some options:
// 1) Use os.Open and pass the file to the image decoder.
// This is a very regular way, but doesn't work on browsers.
// 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
// This works even on browsers.
// 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
// This also works on browsers.
img, _, err := image.Decode(bytes.NewReader(images.Ebiten_png))
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if err != nil {
log.Fatal(err)
}
origEbitenImage, _ := ebiten.NewImageFromImage(img, ebiten.FilterDefault)
w, h := origEbitenImage.Size()
ebitenImage, _ = ebiten.NewImage(w, h, ebiten.FilterDefault)
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op := &ebiten.DrawImageOptions{}
op.ColorM.Scale(1, 1, 1, 0.5)
ebitenImage.DrawImage(origEbitenImage, op)
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for i := range sprites.sprites {
w, h := ebitenImage.Size()
x, y := rand.Intn(screenWidth-w), rand.Intn(screenHeight-h)
vx, vy := 2*rand.Intn(2)-1, 2*rand.Intn(2)-1
a := rand.Intn(maxAngle)
sprites.sprites[i] = &Sprite{
imageWidth: w,
imageHeight: h,
x: x,
y: y,
vx: vx,
vy: vy,
angle: a,
}
}
}
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func leftTouched() bool {
for _, id := range ebiten.TouchIDs() {
x, _ := ebiten.TouchPosition(id)
if x < screenWidth/2 {
return true
}
}
return false
}
func rightTouched() bool {
for _, id := range ebiten.TouchIDs() {
x, _ := ebiten.TouchPosition(id)
if x >= screenWidth/2 {
return true
}
}
return false
}
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func update(screen *ebiten.Image) error {
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// Decrease the nubmer of the sprites.
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if ebiten.IsKeyPressed(ebiten.KeyLeft) || leftTouched() {
sprites.num -= 20
if sprites.num < MinSprites {
sprites.num = MinSprites
}
}
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// Increase the nubmer of the sprites.
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if ebiten.IsKeyPressed(ebiten.KeyRight) || rightTouched() {
sprites.num += 20
if MaxSprites < sprites.num {
sprites.num = MaxSprites
}
}
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sprites.Update()
if ebiten.IsDrawingSkipped() {
return nil
}
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// Draw each sprite.
// DrawImage can be called many many times, but in the implementation,
// the actual draw call to GPU is very few since these calls satisfy
// some conditions e.g. all the rendering sources and targets are same.
// For more detail, see:
// https://pkg.go.dev/github.com/hajimehoshi/ebiten#Image.DrawImage
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w, h := ebitenImage.Size()
for i := 0; i < sprites.num; i++ {
s := sprites.sprites[i]
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op.GeoM.Reset()
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op.GeoM.Translate(-float64(w)/2, -float64(h)/2)
op.GeoM.Rotate(2 * math.Pi * float64(s.angle) / maxAngle)
op.GeoM.Translate(float64(w)/2, float64(h)/2)
op.GeoM.Translate(float64(s.x), float64(s.y))
screen.DrawImage(ebitenImage, op)
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}
msg := fmt.Sprintf(`TPS: %0.2f
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FPS: %0.2f
Num of sprites: %d
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Press <- or -> to change the number of sprites`, ebiten.CurrentTPS(), ebiten.CurrentFPS(), sprites.num)
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ebitenutil.DebugPrint(screen, msg)
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return nil
}
func main() {
if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Sprites (Ebiten Demo)"); err != nil {
log.Fatal(err)
}
}