ebiten/examples/minify/main.go

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// Copyright 2018 The Ebiten 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.
// +build example jsgo
// This example is an experiment to minify images with various filters.
// When linear filter is used, mipmap images should be used for high-quality rendering (#578).
package main
import (
"bytes"
"fmt"
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"image"
_ "image/jpeg"
"log"
"math"
"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/ebitenutil"
"github.com/hajimehoshi/ebiten/examples/resources/images"
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"github.com/hajimehoshi/ebiten/inpututil"
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)
const (
screenWidth = 800
screenHeight = 480
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)
var (
gophersImage *ebiten.Image
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rotate = false
clip = false
counter = 0
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)
func update(screen *ebiten.Image) error {
counter++
if counter == 480 {
counter = 0
}
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if inpututil.IsKeyJustPressed(ebiten.KeyR) {
rotate = !rotate
}
if inpututil.IsKeyJustPressed(ebiten.KeyC) {
clip = !clip
}
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if ebiten.IsDrawingSkipped() {
return nil
}
s := 1.5 / math.Pow(1.01, float64(counter))
msg := fmt.Sprintf(`Minifying images (Nearest filter vs Linear filter):
Press R to rotate the images.
Press C to clip the images.
Scale: %0.2f`, s)
ebitenutil.DebugPrint(screen, msg)
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clippedGophersImage := gophersImage.SubImage(image.Rect(10, 10, 100, 100)).(*ebiten.Image)
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for i, f := range []ebiten.Filter{ebiten.FilterNearest, ebiten.FilterLinear} {
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w, h := gophersImage.Size()
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op := &ebiten.DrawImageOptions{}
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if rotate {
op.GeoM.Translate(-float64(w)/2, -float64(h)/2)
op.GeoM.Rotate(float64(counter) / 300 * 2 * math.Pi)
op.GeoM.Translate(float64(w)/2, float64(h)/2)
}
op.GeoM.Scale(s, s)
op.GeoM.Translate(32+float64(i*w)*s+float64(i*4), 64)
op.Filter = f
if clip {
screen.DrawImage(clippedGophersImage, op)
} else {
screen.DrawImage(gophersImage, op)
}
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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))
if err != nil {
log.Fatal(err)
}
// Specifying filter on NewImage[FromImage] is just for backward compatibility.
// Now specifying filter at DrawImageOptions is recommended.
// Specify FilterDefault here, that means to prefer filter specified at DrawImageOptions.
gophersImage, _ = ebiten.NewImageFromImage(img, ebiten.FilterDefault)
if err := ebiten.Run(update, screenWidth, screenHeight, 1, "Minify (Ebiten Demo)"); err != nil {
log.Fatal(err)
}
}