update source comments of examples

modules/v4d/samples/custom_source_and_sink.cpp

@@ -10,7 +10,7 @@ int main() {
     Ptr<V4D> window = V4D::make(Size(1280, 720), cv::Size(), "Custom Source/Sink");
 
     string hr = "Hello Rainbow!";
-	//Make a Source that generates rainbow frames.
+	//Make a source that generates rainbow frames.
 	Source src([](cv::UMat& frame){
 		static long cnt = 0;
 	    //The source is responsible for initializing the frame..
@@ -20,7 +20,7 @@ int main() {
 	    return true;
 	}, 60.0f);
 
-	//Make a Sink the saves each frame to a PNG file.
+	//Make a sink the saves each frame to a PNG file (does nothing in case of WebAssembly).
 	Sink sink([](const cv::UMat& frame){
 	    try {
 #ifndef __EMSCRIPTEN__
@@ -41,11 +41,10 @@ int main() {
 	window->setSink(sink);
 
 	window->run([=]() {
-	    //Capture video from the Source
 		if(!window->capture())
-			return false; //end of input video
+			return false;
 
-		//Render "Hello Rainbow!" over the frame
+		//Render "Hello Rainbow!" over the video
 		window->nvg([=](const Size& sz) {
 			using namespace cv::v4d::nvg;
 
@@ -56,8 +55,9 @@ int main() {
 			text(sz.width / 2.0, sz.height / 2.0, hr.c_str(), hr.c_str() + hr.size());
 		});
 
-		window->write(); //Write video to the Sink
-		return window->display(); //Display the framebuffer in the native window
+		window->write();
+
+		return window->display();
 	});
 }
 

modules/v4d/samples/display_image.cpp

@@ -5,10 +5,12 @@ using namespace cv;
 using namespace cv::v4d;
 
 int main() {
-    //Creates a V4D window for on screen rendering
+    //Creates a V4D window for on screen rendering with a window size of 720p and a framebuffer of the same size.
+	//Please note that while the window size may change the framebuffer size may not. If you need multiple framebuffer
+	//sizes you need multiple V4D objects
     Ptr<V4D> window = V4D::make(Size(1280, 720), cv::Size(), "Display image");
 
-    //An image
+    //Load an image
 #ifdef __EMSCRIPTEN__
     Mat image = read_embedded_image("doc/lena.png");
 #else
@@ -21,6 +23,7 @@ int main() {
 	window->run([=](){
 	    //Feeds the image to the video pipeline
 	    window->feed(image);
+	    //Displays the framebuffer in the window. Returns false if the windows has been closed.
 	    return window->display();
     });
 }

modules/v4d/samples/display_image_fb.cpp

@@ -5,15 +5,16 @@ using namespace cv;
 using namespace cv::v4d;
 
 int main() {
-    //Creates a V4D object for on screen rendering
+    //Creates a V4D object
     Ptr<V4D> window = V4D::make(Size(1280, 720), cv::Size(), "Display image and FB");
 
-    //Read an image as UMat
+    //Loads an image as a UMat (just in case we have hardware acceleration available)
 #ifdef __EMSCRIPTEN__
     UMat image = read_embedded_image("doc/lena.png").getUMat(ACCESS_READ);
 #else
     UMat image = imread(samples::findFile("lena.jpg")).getUMat(ACCESS_READ);
 #endif
+    //We have to manually resize and color convert the image when using direct frambuffer access.
     UMat resized;
     UMat converted;
     resize(image, resized, window->framebufferSize());
@@ -21,7 +22,10 @@ int main() {
 
 	//Display the framebuffer in the native window in an endless loop
 	window->run([=](){
-	    window->fb([&](UMat& framebuffer){
+		//Create a fb context and copy the prepared image to the framebuffer. The fb context
+		//takes care of retrieving a storing the data on the graphics card (using CL-GL
+		//interop if available), ready for other contexts to use
+		window->fb([&](UMat& framebuffer){
 	        converted.copyTo(framebuffer);
 	    });
 		return window->display();

modules/v4d/samples/font_rendering.cpp

@@ -9,9 +9,8 @@ int main() {
     //The text to render
 	string hw = "Hello World";
 
-    //Display the framebuffer in the native window in an endless loop
     window->run([=](){
-        //Render the text at the center of the screen
+        //Render the text at the center of the screen. Note that you can load you own fonts.
         window->nvg([&](const Size& sz) {
             using namespace cv::v4d::nvg;
             clear();

modules/v4d/samples/font_with_gui.cpp

@@ -25,7 +25,7 @@ int main() {
 	});
 
 	window->run([&]() {
-		//Render the text at the center of the screen
+		//Render the text at the center of the screen using parameters from the GUI.
 		window->nvg([&](const Size& sz) {
 			using namespace cv::v4d::nvg;
 			clear();
@@ -36,7 +36,6 @@ int main() {
 			text(sz.width / 2.0, sz.height / 2.0, hw.c_str(), hw.c_str() + hw.size());
 		});
 
-		//Display the framebuffer in the native window
 		return window->display();
 	});
 }

modules/v4d/samples/render_opengl.cpp

@@ -12,12 +12,10 @@ int main() {
     });
     window->run([=]() {
         window->gl([]() {
-            //Clears the screen
+            //Clears the screen. The clear color and other GL-states are preserved between context-calls.
             glClear(GL_COLOR_BUFFER_BIT);
         });
 
-        //If onscreen rendering is enabled it displays the framebuffer in the native window.
-        //Returns false if the window was closed.
         return window->display();
     });
 }

modules/v4d/samples/vector_graphics.cpp

@@ -6,11 +6,12 @@ using namespace cv::v4d;
 int main() {
     Ptr<V4D> window = V4D::make(Size(1280, 720), cv::Size(), "Vector Graphics");
 
-    //Render the framebuffer in the native window in an endless loop
     window->run([=]() {
-        //Creates a NanoVG context and draws eyes
+        //Creates a NanoVG context and draws googly eyes that occasionally blink.
         window->nvg([](const Size& sz) {
-            //Calls from this namespace may only be used inside a nvg context
+            //Calls from this namespace may only be used inside a nvg context.
+        	//Nvg calls work exactly like their c-funtion counterparts.
+        	//Please refer to the NanoVG documentation for details.
             using namespace cv::v4d::nvg;
             clear();
 

modules/v4d/samples/vector_graphics_and_fb.cpp

@@ -7,9 +7,8 @@ using namespace cv::v4d;
 int main() {
     Ptr<V4D> window = V4D::make(Size(1280, 720), cv::Size(), "Vector Graphics and Framebuffer");
 
-    //Render the framebuffer in the native window in an endless loop
     window->run([=]() {
-        //Creates a NanoVG context and draws eyes
+        //Again creates a NanoVG context and draws googly eyes
         window->nvg([](const Size& sz) {
             //Calls from this namespace may only be used inside a nvg context
             using namespace cv::v4d::nvg;
@@ -93,6 +92,7 @@ int main() {
             fill();
         });
 
+        //Provides the framebuffer as left-off by the nvg context.
         window->fb([](UMat& framebuffer) {
             //Heavily blurs the eyes using a cheap boxFilter
             boxFilter(framebuffer, framebuffer, -1, Size(15, 15), Point(-1,-1), true, BORDER_REPLICATE);

modules/v4d/samples/video_editing.cpp

@@ -31,10 +31,11 @@ int main(int argc, char** argv) {
 #endif
 
     window->run([=]() {
-	    //Capture video from the Source
+	    //Capture video from the source
 		if(!window->capture())
 			return false; //end of input video
 
+		//Render on top of the video
 		window->nvg([=](const Size& sz) {
 			using namespace cv::v4d::nvg;
 
@@ -45,9 +46,10 @@ int main(int argc, char** argv) {
 			text(sz.width / 2.0, sz.height / 2.0, hv.c_str(), hv.c_str() + hv.size());
 		});
 
-		window->write(); //Write video to the Sink
+		//Write video to the sink (do nothing in case of WebAssembly)
+		window->write();
 
-		return window->display(); //Display the framebuffer in the native window
+		return window->display();
 	});
     } catch(std::exception& ex) {
         cerr << ex.what() << endl;