generate screenshot using Xlib.

internal/api/room/handler.go

@@ -61,7 +61,8 @@ func (h *RoomHandler) Route(r chi.Router) {
 	})
 
 	r.Route("/screen", func(r chi.Router) {
-		r.Get("/", h.screenConfiguration)
+		r.With(auth.CanWatchOnly).Get("/", h.screenConfiguration)
+		r.With(auth.CanWatchOnly).Get("/image", h.screenImageGet)
 
 		r.With(auth.AdminsOnly).Post("/", h.screenConfigurationChange)
 		r.With(auth.AdminsOnly).Get("/configurations", h.screenConfigurationsList)

internal/api/room/screen.go

@@ -1,6 +1,9 @@
 package room
 
 import (
+	"bytes"
+	"image/jpeg"
+	"strconv"
 	"net/http"
 
 	"demodesk/neko/internal/types"
@@ -72,3 +75,23 @@ func (h *RoomHandler) screenConfigurationsList(w http.ResponseWriter, r *http.Re
 
 	utils.HttpSuccess(w, list)
 }
+
+func (h *RoomHandler) screenImageGet(w http.ResponseWriter, r *http.Request) {
+	var options *jpeg.Options
+	if quality, err := strconv.Atoi(r.URL.Query().Get("quality")); err == nil {
+		options = &jpeg.Options{ quality }
+	} else {
+		options = &jpeg.Options{ 90 }
+	}
+
+	img := h.desktop.GetScreenshotImage()
+	out := new(bytes.Buffer)
+	err := jpeg.Encode(out, img, options)
+	if err != nil {
+		utils.HttpInternalServerError(w, err)
+		return
+	}
+
+	w.Header().Set("Content-Type", "image/jpeg")
+	w.Write(out.Bytes())
+}

internal/desktop/xorg.go

@@ -1,6 +1,7 @@
 package desktop
 
 import (
+	"image"
 	"regexp"
 	"os/exec"
 
@@ -113,3 +114,7 @@ func (manager *DesktopManagerCtx) GetKeyboardModifiers() types.KeyboardModifiers
 func (manager *DesktopManagerCtx) GetCursorImage() *types.CursorImage {
 	return xorg.GetCursorImage()
 }
+
+func (manager *DesktopManagerCtx) GetScreenshotImage() *image.RGBA {
+	return xorg.GetScreenshotImage()
+}

internal/desktop/xorg/xorg.c

@@ -136,3 +136,33 @@ XFixesCursorImage *XGetCursorImage(void) {
   Display *display = getXDisplay();
   return XFixesGetCursorImage(display);
 }
+
+char *XGetScreenshot(int *w, int *h) {
+  Display *display = getXDisplay();
+  Window root = DefaultRootWindow(display);
+
+  XWindowAttributes attr;
+  XGetWindowAttributes(display, root, &attr);
+  int width = attr.width;
+  int height = attr.height;
+
+  XImage *ximage = XGetImage(display, root, 0, 0, width, height, AllPlanes, ZPixmap);
+
+  *w = width;
+  *h = height;
+  char *pixels = (char *)malloc(width * height * 3);
+
+	for (int row = 0; row < height; row++) {
+		for (int col = 0; col < width; col++) {
+			int pos = ((row * width) + col) * 3;
+      unsigned long pixel = XGetPixel(ximage, col, row);
+
+			pixels[pos]   = (pixel & ximage->red_mask)   >> 16;
+			pixels[pos+1] = (pixel & ximage->green_mask) >> 8;
+			pixels[pos+2] =  pixel & ximage->blue_mask;
+    }
+  }
+
+  XDestroyImage(ximage);
+  return pixels;
+}

internal/desktop/xorg/xorg.go

@@ -13,6 +13,9 @@ import (
 	"time"
 	"unsafe"
 
+	"image"
+	"image/color"
+
 	"demodesk/neko/internal/types"
 )
 
@@ -244,6 +247,34 @@ func GetCursorImage() *types.CursorImage {
 	}
 }
 
+func GetScreenshotImage() *image.RGBA {
+	mu.Lock()
+	defer mu.Unlock()
+
+	var w, h C.int
+	pixelsUnsafe := C.XGetScreenshot(&w, &h)
+	pixels := C.GoBytes(unsafe.Pointer(pixelsUnsafe), w * h * 3)
+	defer C.free(unsafe.Pointer(pixelsUnsafe))
+
+	width := int(w)
+	height := int(h)
+	img := image.NewRGBA(image.Rect(0, 0, width, height))
+	for row := 0; row < height; row++ {
+		for col := 0; col < width; col++ {
+			pos := ((row * width) + col) * 3
+
+			img.SetRGBA(col, row, color.RGBA{
+				R: uint8(pixels[pos]),
+				G: uint8(pixels[pos+1]),
+				B: uint8(pixels[pos+2]),
+				A: 0xFF,
+			})
+		}
+	}
+
+	return img
+}
+
 //export goCreateScreenSize
 func goCreateScreenSize(index C.int, width C.int, height C.int, mwidth C.int, mheight C.int) {
 	ScreenConfigurations[int(index)] = types.ScreenConfiguration{

internal/desktop/xorg/xorg.h

@@ -2,6 +2,7 @@
 
 #include <X11/Xlib.h>
 #include <X11/XKBlib.h>
+#include <X11/Xutil.h>
 #include <X11/extensions/Xrandr.h>
 #include <X11/extensions/XTest.h>
 #include <X11/extensions/Xfixes.h>
@@ -27,3 +28,5 @@ short XGetScreenRate();
 void XSetKeyboardModifier(int mod, int on);
 char XGetKeyboardModifiers();
 XFixesCursorImage *XGetCursorImage(void);
+
+char *XGetScreenshot(int *w, int *h);

internal/http/auth/auth.go

@@ -66,3 +66,14 @@ func CanHostOnly(next http.Handler) http.Handler {
 		}
 	})
 }
+
+func CanWatchOnly(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		session := GetSession(r)
+		if !session.CanWatch() {
+			utils.HttpForbidden(w, "Only for members, that can watch.")
+		} else {
+			next.ServeHTTP(w, r)
+		}
+	})
+}

internal/types/desktop.go

@@ -1,5 +1,9 @@
 package types
 
+import (
+	"image"
+)
+
 type CursorImage struct {
 	Width  uint16
 	Height uint16
@@ -53,6 +57,7 @@ type DesktopManager interface {
 	SetKeyboardModifiers(mod KeyboardModifiers)
 	GetKeyboardModifiers() KeyboardModifiers
 	GetCursorImage() *CursorImage
+	GetScreenshotImage() *image.RGBA
 
 	// xevent
 	OnCursorChanged(listener func(serial uint64))