ebiten/examples/subimage/main.go

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// Copyright 2022 The Ebitengine Authors
//
// 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.
package main
import (
"fmt"
"image"
"image/color"
"log"
"github.com/hajimehoshi/ebiten/v2"
"github.com/hajimehoshi/ebiten/v2/ebitenutil"
)
const (
cx = 32
cy = 32
)
type Game struct {
offscreen *ebiten.Image
subImages [cx][cy]*ebiten.Image
}
func (g *Game) Update() error {
return nil
}
func (g *Game) Draw(screen *ebiten.Image) {
if g.offscreen == nil {
s := screen.Bounds().Size()
g.offscreen = ebiten.NewImage(s.X, s.Y)
}
// Use various sub-images as rendering destination.
// This is a proof-of-concept of efficient rendering with sub-images (#2232).
sw, sh := screen.Bounds().Dx(), screen.Bounds().Dy()
cw := sw / cx
ch := sh / cy
for j := 0; j < cy; j++ {
for i := 0; i < cx; i++ {
img := g.subImages[i][j]
if img == nil {
r := image.Rect(cw*i, ch*j, cw*(i+1), ch*(j+1))
img = g.offscreen.SubImage(r).(*ebiten.Image)
g.subImages[i][j] = img
}
// Rendering onto a sub image should be efficient,
// but this is not efficient some environments like browsers (#2471).
clr := color.RGBA{byte(0xff * float64(i) / cx), byte(0xff * float64(j) / cx), 0, 0xff}
img.Fill(clr)
}
}
screen.DrawImage(g.offscreen, nil)
ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %0.2f, TPS: %0.2f", ebiten.ActualFPS(), ebiten.ActualTPS()))
}
func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
return 640, 480
}
func main() {
ebiten.SetWindowTitle("Sub-images as rendering destinations (Ebitengine Demo)")
if err := ebiten.RunGame(&Game{}); err != nil {
log.Fatal(err)
}
}