Add screen capture device for Linux

pkg/driver/screen/x11_linux.go

@@ -0,0 +1,107 @@
+package screen
+
+import (
+	"fmt"
+	"image"
+	"image/color"
+	"time"
+
+	"github.com/pion/mediadevices/pkg/driver"
+	"github.com/pion/mediadevices/pkg/frame"
+	"github.com/pion/mediadevices/pkg/io/video"
+	"github.com/pion/mediadevices/pkg/prop"
+)
+
+type screen struct {
+	num    int
+	reader *reader
+	tick   *time.Ticker
+}
+
+func deviceID(num int) string {
+	return fmt.Sprintf("X11Screen%d", num)
+}
+
+func init() {
+	dp, err := openDisplay()
+	if err != nil {
+		// No x11 display available.
+		return
+	}
+	defer dp.Close()
+	numScreen := dp.NumScreen()
+	for i := 0; i < numScreen; i++ {
+		driver.GetManager().Register(
+			&screen{
+				num: i,
+			},
+			deviceID(i),
+		)
+	}
+}
+
+func (s *screen) Open() error {
+	r, err := newReader(s.num)
+	if err != nil {
+		return err
+	}
+	s.reader = r
+	return nil
+}
+
+func (s *screen) Close() error {
+	s.reader.Close()
+	if s.tick != nil {
+		s.tick.Stop()
+	}
+	return nil
+}
+
+func (s *screen) VideoRecord(p prop.Media) (video.Reader, error) {
+	rect := s.reader.img.Bounds()
+	w := rect.Max.X - rect.Min.X
+	h := rect.Max.Y - rect.Min.Y
+	imgI444 := image.NewYCbCr(rect, image.YCbCrSubsampleRatio444)
+
+	if p.FrameRate == 0 {
+		p.FrameRate = 10
+	}
+	s.tick = time.NewTicker(time.Duration(float32(time.Second) / p.FrameRate))
+
+	r := video.ReaderFunc(func() (image.Image, error) {
+		<-s.tick.C
+		img := s.reader.Read()
+		// Convert it to I444
+		for y := 0; y < h; y++ {
+			iyBase := y * imgI444.YStride
+			icBase := y * imgI444.CStride
+			for x := 0; x < w; x++ {
+				iy := iyBase + x
+				ic := icBase + x
+				r, g, b, _ := img.At(x, y).RGBA()
+				yy, cb, cr := color.RGBToYCbCr(uint8(r/0x100), uint8(g/0x100), uint8(b/0x100))
+				imgI444.Y[iy] = yy
+				imgI444.Cb[ic] = cb
+				imgI444.Cr[ic] = cr
+			}
+		}
+		return imgI444, nil
+	})
+	return r, nil
+}
+
+func (s *screen) Properties() []prop.Media {
+	rect := s.reader.img.Bounds()
+	w := rect.Max.X - rect.Min.X
+	h := rect.Max.Y - rect.Min.Y
+	return []prop.Media{
+		{
+			DeviceID: deviceID(s.num),
+			Video: prop.Video{
+				Width:       w,
+				Height:      h,
+				FrameFormat: frame.FormatI444,
+			},
+		},
+	}
+}