Refactor V4L2 and X11 grabbers to share more code

Former-commit-id: 46176e53d1acf39f9bd0c0ecbb8e5fb5ab4d45be

libsrc/grabber/CMakeLists.txt

@@ -1,4 +1,3 @@
-
 if (ENABLE_DISPMANX)
 	add_subdirectory(dispmanx)
 endif (ENABLE_DISPMANX)
@@ -6,3 +5,7 @@ endif (ENABLE_DISPMANX)
 if (ENABLE_V4L2)
 	add_subdirectory(v4l2)
 endif (ENABLE_V4L2)
+
+if (ENABLE_X11)
+	add_subdirectory(x11)
+endif()

libsrc/grabber/x11/CMakeLists.txt

@@ -0,0 +1,37 @@
+# Define the current source locations
+SET(CURRENT_HEADER_DIR ${CMAKE_SOURCE_DIR}/include/grabber)
+SET(CURRENT_SOURCE_DIR ${CMAKE_SOURCE_DIR}/libsrc/grabber/x11)
+
+# Find X11
+find_package(X11 REQUIRED)
+
+include_directories(
+	${QT_INCLUDES}
+	${X11_INCLUDES}
+)
+
+SET(X11_QT_HEADERS
+		${CURRENT_HEADER_DIR}/X11Grabber.h
+)
+
+SET(X11_HEADERS
+	${CURRENT_HEADER_DIR}/X11Grabber.h
+)
+
+SET(X11_SOURCES
+		${CURRENT_SOURCE_DIR}/X11Grabber.cpp
+)
+
+QT4_WRAP_CPP(X11_HEADERS_MOC ${X11_QT_HEADERS})
+
+add_library(x11-grabber
+		${X11_HEADERS}
+		${X11_SOURCES}
+		${X11_QT_HEADERS}
+		${X11_HEADERS_MOC}
+)
+
+target_link_libraries(x11-grabber
+	hyperion
+	${QT_LIBRARIES}
+)

libsrc/grabber/x11/X11Grabber.cpp

@@ -0,0 +1,115 @@
+// STL includes
+#include <iostream>
+#include <cstdint>
+
+// X11 includes
+#include <X11/Xutil.h>
+
+// X11Grabber includes
+#include <grabber/X11Grabber.h>
+
+X11Grabber::X11Grabber(const unsigned cropHorizontal, const unsigned cropVertical, const unsigned pixelDecimation) :
+    _pixelDecimation(pixelDecimation),
+    _cropWidth(cropHorizontal),
+    _cropHeight(cropVertical),
+    _x11Display(nullptr),
+    _screenWidth(0),
+    _screenHeight(0),
+    _image(0,0)
+{
+    // empty
+}
+
+X11Grabber::~X11Grabber()
+{
+    if (_x11Display != nullptr)
+    {
+        XCloseDisplay(_x11Display);
+    }
+}
+
+int X11Grabber::open()
+{
+    const char * display_name = nullptr;
+    _x11Display = XOpenDisplay(display_name);
+
+    if (_x11Display == nullptr)
+    {
+        std::cerr << "Failed to open the default X11-display" << std::endl;
+        return -1;
+    }
+
+    return 0;
+}
+
+Image<ColorRgb> & X11Grabber::grab()
+{
+    if (_x11Display == nullptr)
+    {
+        open();
+    }
+
+    updateScreenDimensions();
+
+    const int croppedWidth  = _screenWidth  - 2*_cropWidth;
+    const int croppedHeight = _screenHeight - 2*_cropHeight;
+
+    // Capture the current screen
+    XImage * xImage = XGetImage(_x11Display, DefaultRootWindow(_x11Display), _cropWidth, _cropHeight, croppedWidth, croppedHeight, AllPlanes, ZPixmap);
+    if (xImage == nullptr)
+    {
+        std::cerr << "Grab failed" << std::endl;
+        return _image;
+    }
+
+    // Copy the capture XImage to the local image (and apply required decimation)
+    ColorRgb * outputPtr = _image.memptr();
+    for (int iY=(_pixelDecimation/2); iY<croppedHeight; iY+=_pixelDecimation)
+    {
+        for (int iX=(_pixelDecimation/2); iX<croppedWidth; iX+=_pixelDecimation)
+        {
+            // Extract the pixel from the X11-image
+            const uint32_t pixel = uint32_t(XGetPixel(xImage, iX, iY));
+
+            // Assign the color value
+            outputPtr->red   = uint8_t((pixel >> 16) & 0xff);
+            outputPtr->green = uint8_t((pixel >> 8)  & 0xff);
+            outputPtr->blue  = uint8_t((pixel >> 0)  & 0xff);
+
+            // Move to the next output pixel
+            ++outputPtr;
+        }
+    }
+    // Cleanup allocated resources of the X11 grab
+    XDestroyImage(xImage);
+
+    return _image;
+}
+
+int X11Grabber::updateScreenDimensions()
+{
+    XWindowAttributes window_attributes_return;
+    const Status status = XGetWindowAttributes(_x11Display, DefaultRootWindow(_x11Display), &window_attributes_return);
+    if (status == 0)
+    {
+        std::cerr << "Failed to obtain window attributes" << std::endl;
+        return -1;
+    }
+
+    if (_screenWidth == unsigned(window_attributes_return.width) && _screenHeight == unsigned(window_attributes_return.height))
+    {
+        // No update required
+        return 0;
+    }
+    std::cout << "Update of screen resolution: [" << _screenWidth << "x" << _screenHeight <<"] => ";
+    _screenWidth  = window_attributes_return.width;
+    _screenHeight = window_attributes_return.height;
+    std::cout << "[" << _screenWidth << "x" << _screenHeight <<"]" << std::endl;
+
+    // Update the size of the buffer used to transfer the screenshot
+    int width  = (_screenWidth  - 2 * _cropWidth  + _pixelDecimation/2) / _pixelDecimation;
+    int height = (_screenHeight - 2 * _cropHeight + _pixelDecimation/2) / _pixelDecimation;
+    _image.resize(width, height);
+
+    return 0;
+}