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
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package main
import (
"fmt"
_ "image/png"
"log"
"math/rand"
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"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/ebitenutil"
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)
const (
screenWidth = 320
screenHeight = 240
)
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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}
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 screenWidth <= s.x+s.imageWidth {
s.x = 2*(screenWidth-s.imageWidth) - s.x
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 screenHeight <= s.y+s.imageHeight {
s.y = 2*(screenHeight-s.imageHeight) - s.y
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s.vy = -s.vy
}
}
type Sprites struct {
sprites []*Sprite
num int
}
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func (s *Sprites) Update() {
for _, sprite := range s.sprites {
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sprite.Update()
}
}
const (
MinSprites = 0
MaxSprites = 50000
)
var (
sprites = &Sprites{make([]*Sprite, MaxSprites), 500}
op = &ebiten.DrawImageOptions{}
)
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func update(screen *ebiten.Image) error {
if ebiten.IsKeyPressed(ebiten.KeyLeft) {
sprites.num -= 20
if sprites.num < MinSprites {
sprites.num = MinSprites
}
}
if ebiten.IsKeyPressed(ebiten.KeyRight) {
sprites.num += 20
if MaxSprites < sprites.num {
sprites.num = MaxSprites
}
}
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sprites.Update()
if ebiten.IsRunningSlowly() {
return nil
}
for i := 0; i < sprites.num; i++ {
s := sprites.sprites[i]
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op.GeoM.Reset()
op.GeoM.Translate(float64(s.x), float64(s.y))
screen.DrawImage(ebitenImage, op)
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}
msg := fmt.Sprintf(`FPS: %0.2f
Num of sprites: %d
Press <- or -> to change the number of sprites`, ebiten.CurrentFPS(), sprites.num)
if err := ebitenutil.DebugPrint(screen, msg); err != nil {
return err
}
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return nil
}
func main() {
var err error
img, _, err := ebitenutil.NewImageFromFile("_resources/images/ebiten.png", ebiten.FilterNearest)
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if err != nil {
log.Fatal(err)
}
w, h := img.Size()
ebitenImage, _ = ebiten.NewImage(w, h, ebiten.FilterNearest)
op := &ebiten.DrawImageOptions{}
op.ColorM.Scale(1, 1, 1, 0.5)
ebitenImage.DrawImage(img, op)
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for i := range sprites.sprites {
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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
sprites.sprites[i] = &Sprite{
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imageWidth: w,
imageHeight: h,
x: x,
y: y,
vx: vx,
vy: vy,
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}
}
if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Sprites (Ebiten Demo)"); err != nil {
log.Fatal(err)
}
}