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main.go
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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.
package main
import (
"fmt"
"image"
"image/color"
"log"
"math"
"github.com/hajimehoshi/ebiten/v2"
"github.com/hajimehoshi/ebiten/v2/colorm"
"github.com/hajimehoshi/ebiten/v2/ebitenutil"
)
const (
screenWidth = 640
screenHeight = 480
)
var (
brushImage *ebiten.Image
)
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),
})
}
type touch struct {
id ebiten.TouchID
pos pos
}
type pos struct {
x int
y int
}
type Game struct {
cursor pos
touches []touch
count int
canvasImage *ebiten.Image
}
func NewGame() *Game {
g := &Game{
canvasImage: ebiten.NewImage(screenWidth, screenHeight),
}
g.canvasImage.Fill(color.White)
return g
}
func (g *Game) Update() error {
drawn := false
// Paint the brush by mouse dragging
mx, my := ebiten.CursorPosition()
if ebiten.IsMouseButtonPressed(ebiten.MouseButtonLeft) {
g.paint(g.canvasImage, mx, my)
drawn = true
}
g.cursor = pos{
x: mx,
y: my,
}
// Paint the brush by touches
g.touches = g.touches[:0]
for _, id := range ebiten.AppendTouchIDs(nil) {
x, y := ebiten.TouchPosition(id)
g.paint(g.canvasImage, x, y)
g.touches = append(g.touches, touch{
id: id,
pos: pos{
x: x,
y: y,
},
})
drawn = true
}
if drawn {
g.count++
}
return nil
}
// paint draws the brush on the given canvas image at the position (x, y).
func (g *Game) paint(canvas *ebiten.Image, x, y int) {
op := &colorm.DrawImageOptions{}
op.GeoM.Translate(float64(x), float64(y))
var cm colorm.ColorM
// Scale the color and rotate the hue so that colors vary on each frame.
cm.Scale(1.0, 0.50, 0.125, 1.0)
tps := ebiten.TPS()
theta := 2.0 * math.Pi * float64(g.count%tps) / float64(tps)
cm.RotateHue(theta)
colorm.DrawImage(canvas, brushImage, cm, op)
}
func (g *Game) Draw(screen *ebiten.Image) {
screen.DrawImage(g.canvasImage, nil)
msg := fmt.Sprintf("(%d, %d)", g.cursor.x, g.cursor.y)
for _, t := range g.touches {
msg += fmt.Sprintf("\n(%d, %d) touch %d", t.pos.x, t.pos.y, t.id)
}
ebitenutil.DebugPrint(screen, msg)
}
func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
return screenWidth, screenHeight
}
func main() {
ebiten.SetWindowSize(screenWidth, screenHeight)
ebiten.SetWindowTitle("Paint (Ebitengine Demo)")
if err := ebiten.RunGame(NewGame()); err != nil {
log.Fatal(err)
}
}