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130 lines
3.3 KiB
Go
130 lines
3.3 KiB
Go
package canvas
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import (
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"fmt"
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"syscall/js"
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)
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// Canvas struct holds the Javascript objects needed for the Canvas creation
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type Canvas struct {
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done chan struct{}
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// DOM elements
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window js.Value
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doc js.Value
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body js.Value
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windowSize struct{ width, height float64 }
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// Canvas properties
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canvas js.Value
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ctx js.Value
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reqID js.Value
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renderer js.Func
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// Webcam properties
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navigator js.Value
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video js.Value
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}
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// NewCanvas creates and initializes the new Canvas element
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func NewCanvas() *Canvas {
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var c Canvas
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c.window = js.Global()
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c.doc = c.window.Get("document")
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c.body = c.doc.Get("body")
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c.windowSize.width = c.window.Get("innerWidth").Float()
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c.windowSize.height = c.window.Get("innerHeight").Float()
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c.canvas = c.doc.Call("createElement", "canvas")
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c.canvas.Set("width", c.windowSize.width)
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c.canvas.Set("height", c.windowSize.height)
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c.body.Call("appendChild", c.canvas)
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c.ctx = c.canvas.Call("getContext", "2d")
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return &c
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}
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// Render method calls the `requestAnimationFrame` Javascript function in asynchronous mode.
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func (c *Canvas) Render() {
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var data = make([]byte, int(c.windowSize.width*c.windowSize.height*4))
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go func() {
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c.renderer = js.FuncOf(func(this js.Value, args []js.Value) interface{} {
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c.reqID = c.window.Call("requestAnimationFrame", c.renderer)
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// Draw the canvas frame to the canvas element
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c.ctx.Call("drawImage", c.video, 0, 0)
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rgba := c.ctx.Call("getImageData", 0, 0, c.windowSize.width, c.windowSize.height).Get("data")
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c.Log(rgba.Get("length").Int())
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uint8Arr := js.Global().Get("Uint8Array").New(rgba)
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js.CopyBytesToGo(data, uint8Arr)
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return nil
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})
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c.window.Call("requestAnimationFrame", c.renderer)
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}()
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<-c.done
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}
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// Stop stops the rendering.
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func (c *Canvas) Stop() {
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c.window.Call("cancelAnimationFrame", c.reqID)
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c.done <- struct{}{}
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close(c.done)
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}
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func (c *Canvas) StartWebcam() (*Canvas, error) {
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var err error
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c.video = c.doc.Call("createElement", "video")
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// If we don't do this, the stream will not be played.
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c.video.Set("autoplay", 1)
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c.video.Set("playsinline", 1) // important for iPhones
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// The video should fill out all of the canvas
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c.video.Set("width", 0)
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c.video.Set("height", 0)
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c.body.Call("appendChild", c.video)
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success := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
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c.video.Set("srcObject", args[0])
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c.video.Call("play")
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return nil
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})
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failure := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
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err = fmt.Errorf("failed initialising the camera: %s", args[0].String())
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return nil
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})
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opts := js.Global().Get("Object").New()
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widthOpts := js.Global().Get("Object").New()
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widthOpts.Set("min", 1024)
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widthOpts.Set("max", 1920)
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heightOpts := js.Global().Get("Object").New()
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heightOpts.Set("min", 720)
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heightOpts.Set("max", 1080)
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videoSize := js.Global().Get("Object").New()
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videoSize.Set("width", widthOpts)
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videoSize.Set("height", heightOpts)
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videoSize.Set("aspectRatio", 1.777777778)
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opts.Set("video", videoSize)
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opts.Set("audio", false)
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promise := c.window.Get("navigator").Get("mediaDevices").Call("getUserMedia", opts)
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promise.Call("then", success, failure)
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return c, err
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}
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// Log calls the `console.log` Javascript
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func (c *Canvas) Log(args ...interface{}) {
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c.window.Get("console").Call("log", args...)
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}
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