Include fps + documentatation for Sobel verilated

modified:   tut05/src/main.cpp
new file:   tut05/imgs/sobel_horizontal_160x120.jpg
  tut05/imgs/sobel_vertical_160x120.jpg

sim_fpga/tutorial/tut05/src/main.cpp

@@ -10,6 +10,7 @@
 #include <SDL_opengl.h>
 #include <assert.h>
 #include <stdio.h>
+#include <chrono> // to measure fps
 
 #include <opencv2/opencv.hpp>
 #include <opencv2/core.hpp>
@@ -342,11 +343,18 @@ int main(int argc, char **argv) {
   cv::Mat grayrgb_input_feed; // grayscale resized image, but with 3 channels for the texture
   cv::VideoCapture cap(0);
 
+  double timed_fps;
+  unsigned int millis_elapsed = 0;
+
+  // get opencv frame per seconds (FPS)
+  double cam_fps = cap.get(cv::CAP_PROP_FPS);
 
   if (!cap.isOpened()) {
       std::cout << "cannot open camera";
   }
 
+  auto time_capture = std::chrono::high_resolution_clock::now();
+  auto old_time_capture = std::chrono::high_resolution_clock::now();
   cap >> input_feed;
   cv::resize(input_feed,resized_input_feed,cv::Size(IMG_COLS,IMG_ROWS),cv::INTER_LINEAR);
   cv::cvtColor(resized_input_feed, gray_input_feed, cv::COLOR_BGR2GRAY);
@@ -438,6 +446,8 @@ int main(int argc, char **argv) {
                          GRIP_LINES_VERTICAL_ICON " Set Vertical");
       }
 
+      old_time_capture = time_capture; // save old capture
+      time_capture = std::chrono::high_resolution_clock::now(); // new time capture
       cap >> input_feed;
       cv::resize(input_feed,resized_input_feed,cv::Size(IMG_COLS,IMG_ROWS),cv::INTER_LINEAR);
       cv::cvtColor(resized_input_feed, gray_input_feed, cv::COLOR_BGR2GRAY);
@@ -463,8 +473,15 @@ int main(int argc, char **argv) {
       //ImGui::SameLine();
 
 
+      // the 1st capture will be wrong, but just only the first
+      auto elapsed = std::chrono::duration_cast<std::chrono::milliseconds>(
+                                            time_capture - old_time_capture);
+      millis_elapsed = elapsed.count();
+      timed_fps = 1000.0 / millis_elapsed;
+      ImGui::Text("Timed %i ms (%.1f FPS)", millis_elapsed, timed_fps);
       ImGui::Text("Application average %.3f ms/frame (%.1f FPS)",
                   1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
+      ImGui::Text("Maximum camera fps %.1f", cam_fps);
       ImGui::End();
     }