ebiten/example/game/rects/rects.go

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package rects
import (
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"github.com/hajimehoshi/go-ebiten"
"github.com/hajimehoshi/go-ebiten/graphics"
"github.com/hajimehoshi/go-ebiten/graphics/matrix"
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"image/color"
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"math"
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"math/rand"
"time"
)
type Rects struct {
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rectTextureID graphics.RenderTargetID
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rectTextureInited bool
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offscreenID graphics.RenderTargetID
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offscreenInited bool
rectBounds *graphics.Rect
rectColor *color.RGBA
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}
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const (
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rectTextureWidth = 16
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rectTextureHeight = 16
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offscreenWidth = 256
offscreenHeight = 240
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)
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func New() *Rects {
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return &Rects{
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rectTextureInited: false,
offscreenInited: false,
rectBounds: &graphics.Rect{},
rectColor: &color.RGBA{},
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}
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}
func (game *Rects) Init(tf graphics.TextureFactory) {
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game.rectTextureID = tf.NewRenderTarget(rectTextureWidth, rectTextureHeight)
game.offscreenID = tf.NewRenderTarget(offscreenWidth, offscreenHeight)
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}
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func (game *Rects) Update(context ebiten.GameContext) {
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game.rectBounds.X = rand.Intn(context.ScreenWidth())
game.rectBounds.Y = rand.Intn(context.ScreenHeight())
game.rectBounds.Width =
rand.Intn(context.ScreenWidth() - game.rectBounds.X)
game.rectBounds.Height =
rand.Intn(context.ScreenHeight() - game.rectBounds.Y)
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game.rectColor.R = uint8(rand.Intn(math.MaxUint8))
game.rectColor.G = uint8(rand.Intn(math.MaxUint8))
game.rectColor.B = uint8(rand.Intn(math.MaxUint8))
game.rectColor.A = uint8(rand.Intn(math.MaxUint8))
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}
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func (game *Rects) rectGeometryMatrix() matrix.Geometry {
geometryMatrix := matrix.IdentityGeometry()
scaleX := float64(game.rectBounds.Width) /
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float64(rectTextureWidth)
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scaleY := float64(game.rectBounds.Height) /
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float64(rectTextureHeight)
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geometryMatrix.Scale(scaleX, scaleY)
geometryMatrix.Translate(
float64(game.rectBounds.X), float64(game.rectBounds.Y))
return geometryMatrix
}
func (game *Rects) rectColorMatrix() matrix.Color {
colorMatrix := matrix.IdentityColor()
colorMatrix.Elements[0][0] =
float64(game.rectColor.R) / float64(math.MaxUint8)
colorMatrix.Elements[1][1] =
float64(game.rectColor.G) / float64(math.MaxUint8)
colorMatrix.Elements[2][2] =
float64(game.rectColor.B) / float64(math.MaxUint8)
colorMatrix.Elements[3][3] =
float64(game.rectColor.A) / float64(math.MaxUint8)
return colorMatrix
}
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func (game *Rects) Draw(g graphics.Context) {
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if !game.rectTextureInited {
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g.SetOffscreen(game.rectTextureID)
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g.Fill(255, 255, 255)
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game.rectTextureInited = true
}
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g.SetOffscreen(game.offscreenID)
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if !game.offscreenInited {
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g.Fill(0, 0, 0)
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game.offscreenInited = true
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}
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g.DrawTexture(g.TextureID(game.rectTextureID),
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game.rectGeometryMatrix(),
game.rectColorMatrix())
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g.ResetOffscreen()
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g.DrawTexture(g.TextureID(game.offscreenID),
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matrix.IdentityGeometry(),
matrix.IdentityColor())
}
func init() {
rand.Seed(time.Now().UnixNano())
}