ebiten/examples/blur/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
package main
import (
"bytes"
"image"
_ "image/jpeg"
"log"
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"github.com/hajimehoshi/ebiten/v2"
"github.com/hajimehoshi/ebiten/v2/examples/resources/images"
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)
const (
screenWidth = 640
screenHeight = 480
)
var (
gophersImage *ebiten.Image
)
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type Game struct{}
func (g *Game) Update() error {
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return nil
}
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func (g *Game) Draw(screen *ebiten.Image) {
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op := &ebiten.DrawImageOptions{}
op.GeoM.Translate(0, 0)
screen.DrawImage(gophersImage, op)
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// Box blur (7x7)
// https://en.wikipedia.org/wiki/Box_blur
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for j := -3; j <= 3; j++ {
for i := -3; i <= 3; i++ {
op := &ebiten.DrawImageOptions{}
op.GeoM.Translate(float64(i), 244+float64(j))
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// Alpha scale should be 1.0/49.0, but accumulating 1/49 49 times doesn't reach to 1, because
// the final color is affected by the destination alpha when CompositeModeSourceOver is used.
// This composite mode is the default mode. See how this is calculated at the doc:
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// https://pkg.go.dev/github.com/hajimehoshi/ebiten/v2#CompositeMode
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//
// Use a higher value than 1.0/49.0. Here, 1.0/25.0 here to get a reasonable result.
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op.ColorM.Scale(1, 1, 1, 1.0/25.0)
screen.DrawImage(gophersImage, op)
}
}
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}
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func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
return screenWidth, screenHeight
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}
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.FiveYears_jpg))
if err != nil {
log.Fatal(err)
}
gophersImage, _ = ebiten.NewImageFromImage(img)
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ebiten.SetWindowSize(screenWidth, screenHeight)
ebiten.SetWindowTitle("Blur (Ebiten Demo)")
if err := ebiten.RunGame(&Game{}); err != nil {
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log.Fatal(err)
}
}