ebiten/examples/perspective/main.go

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// Copyright 2014 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.
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// +build example jsgo
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package main
import (
"bytes"
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"image"
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_ "image/jpeg"
"log"
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"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/examples/resources/images"
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)
const (
screenWidth = 320
screenHeight = 240
)
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var (
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gophersImage *ebiten.Image
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)
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func update(screen *ebiten.Image) error {
if ebiten.IsDrawingSkipped() {
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return nil
}
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// Split the image into horizontal lines and draw them with different scales.
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op := &ebiten.DrawImageOptions{}
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w, h := gophersImage.Size()
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for i := 0; i < h; i++ {
op.GeoM.Reset()
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// Move the image's center to the upper-left corner.
op.GeoM.Translate(-float64(w)/2, -float64(h)/2)
// Scale each lines and adjust the position.
lineW := w + i*3/4
x := -float64(lineW) / float64(w) / 2
op.GeoM.Scale(float64(lineW)/float64(w), 1)
op.GeoM.Translate(x, float64(i))
// Move the image's center to the screen's center.
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op.GeoM.Translate(screenWidth/2, screenHeight/2)
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screen.DrawImage(gophersImage.SubImage(image.Rect(0, i, w, i+1)).(*ebiten.Image), op)
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}
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return nil
}
func main() {
// 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.Gophers_jpg))
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if err != nil {
log.Fatal(err)
}
gophersImage, _ = ebiten.NewImageFromImage(img, ebiten.FilterDefault)
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if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Perspective (Ebiten Demo)"); err != nil {
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log.Fatal(err)
}
}