add xor example

This commit is contained in:
faiface 2017-04-15 17:10:35 +02:00
parent 1887237881
commit d0481dc0cf
3 changed files with 82 additions and 0 deletions

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xor/README.md Normal file
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# Xor
This example demonstrates an unusual Porter-Duff composition method: Xor. (And the capability of
drawing circles.)
![Screenshot](screenshot.png)

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xor/main.go Normal file
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package main
import (
"math"
"time"
"github.com/faiface/pixel"
"github.com/faiface/pixel/imdraw"
"github.com/faiface/pixel/pixelgl"
"golang.org/x/image/colornames"
)
func run() {
cfg := pixelgl.WindowConfig{
Title: "Xor",
Bounds: pixel.R(0, 0, 1024, 768),
Resizable: true,
VSync: true,
}
win, err := pixelgl.NewWindow(cfg)
if err != nil {
panic(err)
}
imd := imdraw.New(nil)
canvas := pixelgl.NewCanvas(win.Bounds())
start := time.Now()
for !win.Closed() {
// in case window got resized, we also need to resize out canvas
canvas.SetBounds(win.Bounds())
offset := math.Sin(time.Since(start).Seconds()) * 300
// clear the canvas to be totally transparent and set the xor compose method
canvas.Clear(pixel.Alpha(0))
canvas.SetComposeMethod(pixel.ComposeXor)
// red circle
imd.Clear()
imd.Color(pixel.RGB(1, 0, 0))
imd.Push(pixel.X(-offset) + win.Bounds().Center())
imd.Circle(200, 0)
imd.Draw(canvas)
// blue circle
imd.Clear()
imd.Color(pixel.RGB(0, 0, 1))
imd.Push(pixel.X(offset) + win.Bounds().Center())
imd.Circle(150, 0)
imd.Draw(canvas)
// yellow circle
imd.Clear()
imd.Color(pixel.RGB(1, 1, 0))
imd.Push(pixel.Y(-offset) + win.Bounds().Center())
imd.Circle(100, 0)
imd.Draw(canvas)
// magenta circle
imd.Clear()
imd.Color(pixel.RGB(1, 0, 1))
imd.Push(pixel.Y(offset) + win.Bounds().Center())
imd.Circle(50, 0)
imd.Draw(canvas)
win.Clear(colornames.Green)
canvas.Draw(win)
win.Update()
}
}
func main() {
pixelgl.Run(run)
}

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