ebiten/examples/paint/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 (
"fmt"
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"image"
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"image/color"
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"log"
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"math"
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"github.com/hajimehoshi/ebiten"
"github.com/hajimehoshi/ebiten/ebitenutil"
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)
const (
screenWidth = 320
screenHeight = 240
)
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var (
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count int
brushImage *ebiten.Image
canvasImage *ebiten.Image
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)
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func init() {
const (
a0 = 0x40
a1 = 0xc0
a2 = 0xff
)
pixels := []uint8{
a0, a1, a1, a0,
a1, a2, a2, a1,
a1, a2, a2, a1,
a0, a1, a1, a0,
}
brushImage, _ = ebiten.NewImageFromImage(&image.Alpha{
Pix: pixels,
Stride: 4,
Rect: image.Rect(0, 0, 4, 4),
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}, ebiten.FilterDefault)
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canvasImage, _ = ebiten.NewImage(screenWidth, screenHeight, ebiten.FilterDefault)
canvasImage.Fill(color.White)
}
// paint draws the brush on the given canvas image at the position (x, y).
func paint(canvas *ebiten.Image, x, y int) {
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op := &ebiten.DrawImageOptions{}
op.GeoM.Translate(float64(x), float64(y))
// Scale the color and rotate the hue so that colors vary on each frame.
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op.ColorM.Scale(1.0, 0.50, 0.125, 1.0)
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theta := 2.0 * math.Pi * float64(count%ebiten.FPS) / ebiten.FPS
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op.ColorM.RotateHue(theta)
canvas.DrawImage(brushImage, op)
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}
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func update(screen *ebiten.Image) error {
drawn := false
// Paint the brush by mouse dragging
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mx, my := ebiten.CursorPosition()
if ebiten.IsMouseButtonPressed(ebiten.MouseButtonLeft) {
paint(canvasImage, mx, my)
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drawn = true
}
// Paint the brush by touches
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for _, t := range ebiten.Touches() {
x, y := t.Position()
paint(canvasImage, x, y)
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drawn = true
}
if drawn {
count++
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}
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if ebiten.IsRunningSlowly() {
return nil
}
screen.DrawImage(canvasImage, nil)
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msg := fmt.Sprintf("(%d, %d)", mx, my)
for _, t := range ebiten.Touches() {
x, y := t.Position()
msg += fmt.Sprintf("\n(%d, %d) touch %d", x, y, t.ID())
}
ebitenutil.DebugPrint(screen, msg)
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return nil
}
func main() {
if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Paint (Ebiten Demo)"); err != nil {
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log.Fatal(err)
}
}