mirror of
https://github.com/hajimehoshi/ebiten.git
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96 lines
2.6 KiB
Go
96 lines
2.6 KiB
Go
// Copyright 2020 The Ebiten Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build example
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package main
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import (
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"bytes"
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"image"
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_ "image/jpeg"
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"log"
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"math"
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"github.com/hajimehoshi/ebiten/v2"
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"github.com/hajimehoshi/ebiten/v2/examples/resources/images"
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)
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const (
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screenWidth = 640
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screenHeight = 480
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)
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var (
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gophersImage *ebiten.Image
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)
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type Game struct {
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count int
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}
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func (g *Game) Update() error {
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g.count++
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return nil
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}
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func (g *Game) Draw(screen *ebiten.Image) {
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w, h := gophersImage.Size()
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op := &ebiten.DrawImageOptions{}
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// Move the image's center to the screen's upper-left corner.
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// This is a preparation for rotating. When geometry matrices are applied,
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// the origin point is the upper-left corner.
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op.GeoM.Translate(-float64(w)/2, -float64(h)/2)
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// Rotate the image. As a result, the anchor point of this rotate is
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// the center of the image.
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op.GeoM.Rotate(float64(g.count%360) * 2 * math.Pi / 360)
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// Move the image to the screen's center.
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op.GeoM.Translate(screenWidth/2, screenHeight/2)
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// Use SubImage to clip the rendering region.
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const size = 60
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r := image.Rect(320-size, 240-size, 320+size, 240+size)
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screen.SubImage(r).(*ebiten.Image).DrawImage(gophersImage, op)
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}
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func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
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return screenWidth, screenHeight
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}
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func main() {
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// Decode image from a byte slice instead of a file so that
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// this example works in any working directory.
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// If you want to use a file, there are some options:
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// 1) Use os.Open and pass the file to the image decoder.
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// This is a very regular way, but doesn't work on browsers.
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// 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
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// This works even on browsers.
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// 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
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// This also works on browsers.
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img, _, err := image.Decode(bytes.NewReader(images.Gophers_jpg))
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if err != nil {
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log.Fatal(err)
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}
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gophersImage = ebiten.NewImageFromImage(img)
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ebiten.SetWindowSize(screenWidth, screenHeight)
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ebiten.SetWindowTitle("Clip (Ebiten Demo)")
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if err := ebiten.RunGame(&Game{}); err != nil {
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log.Fatal(err)
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}
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}
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