ace/drivers/video/ppm.go

package video

import (
	"context"
	"image"
	"image/draw"
	"io"
	"time"

	"github.com/pion/mediadevices/pkg/frame"
	"github.com/pion/mediadevices/pkg/io/video"
	"github.com/pion/mediadevices/pkg/prop"
	"github.com/sirupsen/logrus"

	_ "github.com/jbuchbinder/gopnm"
)

const DefaultFPS float32 = 60.0

type Frame struct {
	Time  time.Time
	Image io.ReadCloser
}

type PPMStreamDriver struct {
	Height, Width int
	FPS           float32
	PPMImage      <-chan Frame
	closed        <-chan struct{}
	cancel        func()
}

func (v *PPMStreamDriver) Open() error {
	defer logrus.Debug("device opened")
	ctx, cancel := context.WithCancel(context.Background())
	v.closed = ctx.Done()
	v.cancel = cancel
	return nil
}

func (v *PPMStreamDriver) Close() error {
	v.cancel()
	return nil
}

func (v *PPMStreamDriver) Properties() []prop.Media {
	return []prop.Media{
		{
			Video: prop.Video{
				Width:       v.Width,
				Height:      v.Height,
				FrameRate:   v.FPS,
				FrameFormat: frame.FormatYUYV,
			},
		},
	}
}

func (v *PPMStreamDriver) VideoRecord(p prop.Media) (video.Reader, error) {
	logrus.Debug(p)
	/*canvas := image.NewYCbCr(
		image.Rect(0, 0, p.Width, p.Height),
		image.YCbCrSubsampleRatio420,
	)

	Y, Cb, Cr := color.RGBToYCbCr(0, 0, 0)
	for y := 0; y < canvas.Rect.Dy(); y++ {
		for x := 0; x < canvas.Rect.Dx(); x++ {
			canvas.Y[canvas.YOffset(x, y)] = Y
			canvas.Cb[canvas.COffset(x, y)] = Cb
			canvas.Cr[canvas.COffset(x, y)] = Cr
		}
	}*/

	canvas := image.NewRGBA(image.Rect(0, 0, p.Width, p.Height))
	var (
		prevHeight, prevWidth int
	)

	r := video.ReaderFunc(func() (img image.Image, release func(), err error) {
		select {
		case <-v.closed:
			return nil, func() {}, io.EOF
		case ppmF := <-v.PPMImage:
			defer ppmF.Image.Close()

			// skip timeouted frame
			if time.Since(ppmF.Time) > time.Second/time.Duration(p.FrameRate) {
				return canvas, func() {}, nil
			}

			img, _, err := image.Decode(ppmF.Image)
			if err != nil {
				return nil, func() {}, err
			}

			// screen geometroy change
			if img.Bounds().Dx() != prevWidth || img.Bounds().Dy() != prevHeight {
				draw.Draw(canvas, canvas.Rect, image.Black, image.Black.Bounds().Min, draw.Over)
				prevWidth = img.Bounds().Dx()
				prevHeight = img.Bounds().Dy()
			}

			offsetX := (canvas.Rect.Dx() - img.Bounds().Dx()) / 2
			offsetY := (canvas.Rect.Dy() - img.Bounds().Dy()) / 2

			draw.Draw(canvas, image.Rect(
				offsetX, offsetY, offsetX+img.Bounds().Dx(), offsetY+img.Bounds().Dy(),
			), img, img.Bounds().Min, draw.Over)
		case <-time.After(time.Second / time.Duration(p.FrameRate)):
		default:
		}
		return canvas, func() {}, nil
	})
	return r, nil
}