pigo-wasm-demos/wasm/canvas.go

package wasm

import (
	"fmt"
	"math"
	"syscall/js"

	"github.com/esimov/pigo-wasm-demos/detector"
)

// Canvas struct holds the Javascript objects needed for the Canvas creation
type Canvas struct {
	done   chan struct{}
	succCh chan struct{}
	errCh  chan error

	// DOM elements
	window     js.Value
	doc        js.Value
	body       js.Value
	windowSize struct{ width, height int }

	// Canvas properties
	canvas   js.Value
	ctx      js.Value
	reqID    js.Value
	renderer js.Func

	// Webcam properties
	navigator js.Value
	video     js.Value

	showPupil  bool
	showCoord  bool
	flploc     bool
	markerType string
	markerIdx  int
}

var det *detector.Detector

// NewCanvas creates and initializes the new Canvas element
func NewCanvas() *Canvas {
	var c Canvas
	c.window = js.Global()
	c.doc = c.window.Get("document")
	c.body = c.doc.Get("body")

	c.windowSize.width = 1024
	c.windowSize.height = 640

	c.canvas = c.doc.Call("createElement", "canvas")
	c.canvas.Set("width", c.windowSize.width)
	c.canvas.Set("height", c.windowSize.height)
	c.canvas.Set("id", "canvas")
	c.body.Call("appendChild", c.canvas)

	c.ctx = c.canvas.Call("getContext", "2d")
	c.showPupil = true
	c.showCoord = false
	c.flploc = false
	c.markerType = "rect"

	det = detector.NewDetector()
	return &c
}

// Render calls the `requestAnimationFrame` Javascript function in asynchronous mode.
func (c *Canvas) Render() error {
	width, height := c.windowSize.width, c.windowSize.height
	var data = make([]byte, width*height*4)
	c.done = make(chan struct{})

	err := det.UnpackCascades()
	if err != nil {
		return err
	}
	c.renderer = js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		go func() {
			c.window.Get("stats").Call("begin")

			c.reqID = c.window.Call("requestAnimationFrame", c.renderer)
			// Draw the webcam frame to the canvas element
			c.ctx.Call("drawImage", c.video, 0, 0)
			rgba := c.ctx.Call("getImageData", 0, 0, width, height).Get("data")

			// Convert the rgba value of type Uint8ClampedArray to Uint8Array in order to
			// be able to transfer it from Javascript to Go via the js.CopyBytesToGo function.
			uint8Arr := js.Global().Get("Uint8Array").New(rgba)
			js.CopyBytesToGo(data, uint8Arr)
			pixels := c.rgbaToGrayscale(data)

			// Empty the data slice to avoid unnecessary memory allocation.
			// Otherwise, the GC won't clean up the memory address allocated by this slice
			// and the memory will keep up increasing by each iteration.
			data = make([]byte, len(data))

			res := det.DetectFaces(pixels, height, width)
			c.drawDetection(res)

			c.window.Get("stats").Call("end")
		}()
		return nil
	})
	// Release renderer to free up resources.
	defer c.renderer.Release()

	c.window.Call("requestAnimationFrame", c.renderer)
	c.detectKeyPress()
	<-c.done
	return nil
}

// Stop stops the rendering.
func (c *Canvas) Stop() {
	c.window.Call("cancelAnimationFrame", c.reqID)
	c.done <- struct{}{}
	close(c.done)
}

// StartWebcam reads the webcam data and feeds it into the canvas element.
// It returns an empty struct in case of success and error in case of failure.
func (c *Canvas) StartWebcam() (*Canvas, error) {
	var err error
	c.succCh = make(chan struct{})
	c.errCh = make(chan error)

	c.video = c.doc.Call("createElement", "video")

	// If we don't do this, the stream will not be played.
	c.video.Set("autoplay", 1)
	c.video.Set("playsinline", 1) // important for iPhones

	// The video should fill out all of the canvas
	c.video.Set("width", 0)
	c.video.Set("height", 0)

	c.body.Call("appendChild", c.video)

	success := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		go func() {
			c.video.Set("srcObject", args[0])
			c.video.Call("play")
			c.succCh <- struct{}{}
		}()
		return nil
	})

	failure := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		go func() {
			err = fmt.Errorf("failed initialising the camera: %s", args[0].String())
			c.errCh <- err
		}()
		return nil
	})

	opts := js.Global().Get("Object").New()

	videoSize := js.Global().Get("Object").New()
	videoSize.Set("width", c.windowSize.width)
	videoSize.Set("height", c.windowSize.height)
	videoSize.Set("aspectRatio", 1.777777778)

	opts.Set("video", videoSize)
	opts.Set("audio", false)

	promise := c.window.Get("navigator").Get("mediaDevices").Call("getUserMedia", opts)
	promise.Call("then", success, failure)

	select {
	case <-c.succCh:
		return c, nil
	case err := <-c.errCh:
		return nil, err
	}
}

// rgbaToGrayscale converts the rgb pixel values to grayscale
func (c *Canvas) rgbaToGrayscale(data []uint8) []uint8 {
	rows, cols := c.windowSize.width, c.windowSize.height
	for r := 0; r < rows; r++ {
		for c := 0; c < cols; c++ {
			// gray = 0.2*red + 0.7*green + 0.1*blue
			data[r*cols+c] = uint8(math.Round(
				0.2126*float64(data[r*4*cols+4*c+0]) +
					0.7152*float64(data[r*4*cols+4*c+1]) +
					0.0722*float64(data[r*4*cols+4*c+2])))
		}
	}
	return data
}

// drawDetection draws the detected faces and eyes.
func (c *Canvas) drawDetection(dets [][]int) {
	for i := 0; i < len(dets); i++ {
		if dets[i][3] > 50 {
			c.ctx.Call("beginPath")
			c.ctx.Set("lineWidth", 3)
			c.ctx.Set("strokeStyle", "red")

			row, col, scale := dets[i][1], dets[i][0], dets[i][2]
			if c.showCoord {
				c.ctx.Set("fillStyle", "red")
				c.ctx.Set("font", "18px Arial")
				message := fmt.Sprintf("(%v, %v)", row-scale/2, col-scale/2)
				txtWidth := c.ctx.Call("measureText", js.ValueOf(message)).Get("width").Int()
				c.ctx.Call("fillText", message, (row-scale/2)-txtWidth/2, col-scale/2-10)
			}
			switch c.markerType {
			case "rect":
				c.ctx.Call("rect", row-scale/2, col-scale/2, scale, scale)
			case "circle":
				c.ctx.Call("moveTo", row+int(scale/2), col)
				c.ctx.Call("arc", row, col, scale/2, 0, 2*math.Pi, true)
			case "ellipse":
				c.ctx.Call("moveTo", row+int(scale/2), col)
				c.ctx.Call("ellipse", row, col, scale/2, float64(scale)/1.6, 0, 0, 2*math.Pi)
			}
			c.ctx.Call("stroke")

			if c.showPupil {
				leftPupil := det.DetectLeftPupil(dets[i])
				if leftPupil != nil {
					col, row, scale := leftPupil.Col, leftPupil.Row, leftPupil.Scale/8
					c.ctx.Call("moveTo", col+int(scale), row)
					c.ctx.Call("arc", col, row, scale, 0, 2*math.Pi, true)
				}

				rightPupil := det.DetectRightPupil(dets[i])
				if rightPupil != nil {
					col, row, scale := rightPupil.Col, rightPupil.Row, rightPupil.Scale/8
					c.ctx.Call("moveTo", col+int(scale), row)
					c.ctx.Call("arc", col, row, scale, 0, 2*math.Pi, true)
				}
				c.ctx.Call("stroke")

				if c.flploc {
					flps := det.DetectLandmarkPoints(leftPupil, rightPupil)
					c.ctx.Call("beginPath")
					c.ctx.Set("fillStyle", "rgb(0, 255, 0)")
					for _, flp := range flps {
						if len(flp) > 0 {
							col, row, scale = flp[1], flp[0], flp[2]/7
							c.ctx.Call("moveTo", row, col)
							c.ctx.Call("arc", row, col, scale, 0, 2*math.Pi, false)
						}
					}
					c.ctx.Call("fill")
				}
			}
		}
	}
}

// detectKeyPress listen for the keypress event and retrieves the key code.
func (c *Canvas) detectKeyPress() {
	keyEventHandler := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		keyCode := args[0].Get("key")
		switch {
		case keyCode.String() == "e":
			c.showPupil = !c.showPupil
		case keyCode.String() == "c":
			c.markerIdx++
			if c.markerIdx > 2 {
				c.markerIdx = 0
			}
			if c.markerIdx == 0 {
				c.markerType = "rect"
			} else if c.markerIdx == 1 {
				c.markerType = "circle"
			} else if c.markerIdx == 2 {
				c.markerType = "ellipse"
			}
		case keyCode.String() == "f":
			c.flploc = !c.flploc
		case keyCode.String() == "x":
			c.showCoord = !c.showCoord
		}
		return nil
	})
	c.doc.Call("addEventListener", "keypress", keyEventHandler)
}

// Log calls the `console.log` Javascript function
func (c *Canvas) Log(args ...interface{}) {
	c.window.Get("console").Call("log", args...)
}

// Alert calls the `alert` Javascript function
func (c *Canvas) Alert(args ...interface{}) {
	alert := c.window.Get("alert")
	alert.Invoke(args...)
}