refactoring, renaming and commenting

modules/viz2d/include/opencv2/viz2d/viz2d.hpp

@@ -101,6 +101,9 @@ template<typename T> void find_widgets(nanogui::Widget* parent, std::vector<T>&
  */
 CV_EXPORTS cv::Scalar colorConvert(const cv::Scalar& src, cv::ColorConversionCodes code);
 
+CV_EXPORTS void resizeKeepAspectRatio(const cv::UMat& src, cv::UMat& output, const cv::Size& dstSize,
+        const cv::Scalar& bgcolor = {0,0,0,255});
+
 using namespace cv::viz::detail;
 
 class NVG;
@@ -119,8 +122,6 @@ CV_EXPORTS class Viz2D {
     int minor_;
     int samples_;
     bool debug_;
-    std::filesystem::path capturePath_;
-    std::filesystem::path writerPath_;
     GLFWwindow* glfwWindow_ = nullptr;
     FrameBufferContext* clglContext_ = nullptr;
     CLVAContext* clvaContext_ = nullptr;
@@ -144,7 +145,8 @@ public:
      * @param title The window title.
      * @param debug Create a debug OpenGL context.
      */
-    CV_EXPORTS static cv::Ptr<Viz2D> make(const cv::Size& size, const string& title, bool debug = false);
+    CV_EXPORTS static cv::Ptr<Viz2D> make(const cv::Size& size, const string& title, bool debug =
+            false);
 
     /*!
      * Creates a Viz2D object which is the central object to perform visualizations with.
@@ -157,8 +159,9 @@ public:
      * @param samples MSAA samples.
      * @param debug Create a debug OpenGL context.
      */
-    CV_EXPORTS static cv::Ptr<Viz2D> make(const cv::Size& initialSize, const cv::Size& frameBufferSize, bool offscreen,
-            const string& title, int major = 4, int minor = 6, int samples = 0, bool debug = false);
+    CV_EXPORTS static cv::Ptr<Viz2D> make(const cv::Size& initialSize,
+            const cv::Size& frameBufferSize, bool offscreen, const string& title, int major = 4,
+            int minor = 6, int samples = 0, bool debug = false);
     /*!
      * Default destructor
      */
@@ -203,18 +206,18 @@ public:
      */
     CV_EXPORTS void nvg(std::function<void(const cv::Size&)> fn);
     /*!
-       * Execute function object fn inside a nanogui context.
-       * The context provides a #cv::viz::FormHelper instance to the function object
-       * which can be used to build a gui.
-       * @param fn A function that is passed the size of the framebuffer
-       * and performs drawing using cv::viz::nvg.
-       */
+     * Execute function object fn inside a nanogui context.
+     * The context provides a #cv::viz::FormHelper instance to the function object
+     * which can be used to build a gui.
+     * @param fn A function that is passed the size of the framebuffer
+     * and performs drawing using cv::viz::nvg.
+     */
     CV_EXPORTS void nanogui(std::function<void(FormHelper& form)> fn);
     /*!
-       * Execute function object fn in a loop.
-       * This function main purpose is to abstract the run loop for portability reasons.
-       * @param fn A functor that will be called repeatetly until the application terminates or the functor returns false
-       */
+     * Execute function object fn in a loop.
+     * This function main purpose is to abstract the run loop for portability reasons.
+     * @param fn A functor that will be called repeatetly until the application terminates or the functor returns false
+     */
     CV_EXPORTS void run(std::function<bool()> fn);
 
     /*!

modules/viz2d/samples/cpp/display_image_fb.cpp

@@ -0,0 +1,24 @@
+#include <opencv2/viz2d/viz2d.hpp>
+
+using namespace cv;
+using namespace cv::viz;
+
+constexpr int WIDTH = 1280;
+constexpr int HEIGHT = 720;
+
+int main() {
+	//Creates a Viz2D object for on screen rendering
+	Ptr<Viz2D> v2d = Viz2D::make(Size(WIDTH, HEIGHT), "Show image");
+	//Read an image as UMat
+	UMat image = imread(samples::findFile("lena.jpg")).getUMat(ACCESS_READ);
+	UMat resized;
+	//Resize the image to framebuffer size
+	resize(image, resized, v2d->getFrameBufferSize());
+	v2d->fb([&](const UMat& framebuffer) {
+		//Color convert the resized UMat. The framebuffer has alpha.
+		cvtColor(resized, framebuffer, COLOR_RGB2BGRA);
+	});
+	//Display the framebuffer in the native window
+	while(v2d->display());
+}
+

modules/viz2d/src/detail/clvacontext.cpp

@@ -43,7 +43,7 @@ bool CLVAContext::capture(std::function<void(cv::UMat&)> fn) {
             return false;
 
         cv::Size fbSize = clglContext_.getSize();
-        cv::resize(videoFrame_, rgbBuffer_, fbSize);
+        resizeKeepAspectRatio(videoFrame_, rgbBuffer_, fbSize);
         cv::cvtColor(rgbBuffer_, frameBuffer_, cv::COLOR_RGB2BGRA);
 
         assert(frameBuffer_.size() == fbSize);

modules/viz2d/src/viz2d.cpp

@@ -47,14 +47,32 @@ cv::Scalar colorConvert(const cv::Scalar& src, cv::ColorConversionCodes code) {
     return dst;
 }
 
+void resizeKeepAspectRatio(const cv::UMat& src, cv::UMat& output, const cv::Size& dstSize,
+        const cv::Scalar& bgcolor) {
+    double h1 = dstSize.width * (src.rows / (double) src.cols);
+    double w2 = dstSize.height * (src.cols / (double) src.rows);
+    if (h1 <= dstSize.height) {
+        cv::resize(src, output, cv::Size(dstSize.width, h1));
+    } else {
+        cv::resize(src, output, cv::Size(w2, dstSize.height));
+    }
+
+    int top = (dstSize.height - output.rows) / 2;
+    int down = (dstSize.height - output.rows + 1) / 2;
+    int left = (dstSize.width - output.cols) / 2;
+    int right = (dstSize.width - output.cols + 1) / 2;
+
+    cv::copyMakeBorder(output, output, top, down, left, right, cv::BORDER_CONSTANT, bgcolor);
+}
+
 cv::Ptr<Viz2D> Viz2D::make(const cv::Size& size, const string& title, bool debug) {
     cv::Ptr<Viz2D> v2d = new Viz2D(size, size, false, title, 4, 6, 0, debug);
     v2d->setVisible(true);
     return v2d;
 }
 
-cv::Ptr<Viz2D> Viz2D::make(const cv::Size& initialSize, const cv::Size& frameBufferSize, bool offscreen,
-            const string& title, int major, int minor, int samples, bool debug) {
+cv::Ptr<Viz2D> Viz2D::make(const cv::Size& initialSize, const cv::Size& frameBufferSize,
+        bool offscreen, const string& title, int major, int minor, int samples, bool debug) {
     return new Viz2D(initialSize, frameBufferSize, offscreen, title, major, minor, samples, debug);
 }
 
@@ -195,11 +213,11 @@ bool Viz2D::initializeWindowing() {
         find_widgets(&v2d->screen(), widgets);
         for (auto* w : widgets) {
             auto mousePos = nanogui::Vector2i(v2d->getMousePosition()[0] / v2d->getXPixelRatio(), v2d->getMousePosition()[1] / v2d->getYPixelRatio());
-            if(contains_absolute(w, mousePos)) {
-                v2d->screen().scroll_callback_event(x, y);
-                return;
-            }
-        }
+    if(contains_absolute(w, mousePos)) {
+        v2d->screen().scroll_callback_event(x, y);
+        return;
+    }
+}
 
         v2d->zoom(y < 0 ? 1.1 : 0.9);
     }
@@ -295,13 +313,13 @@ void Viz2D::nanogui(std::function<void(FormHelper& form)> fn) {
 
 void Viz2D::run(std::function<bool()> fn) {
 #ifndef __EMSCRIPTEN__
-    while(keepRunning() && fn());
+    while (keepRunning() && fn())
+        ;
 #else
     emscripten_set_main_loop(fn, -1, true);
 #endif
 }
 
-
 void Viz2D::setSource(const Source& src) {
     if (!clva().hasContext())
         clva().copyContext();