Merge pull request #7140 from Asalle:fix-7136-Bounding_Box_explanation

2016-08-29 08:42:02 +00:00
parent a21b8ed92c ec5ae4af1d
commit a278abdc76
2 changed files with 83 additions and 14 deletions
@@ -22,6 +22,49 @@ This tutorial code's is shown lines below. You can also download it from
 Explanation
 -----------

+The main function is rather simple, as follows from the comments we do the following:
+-#  Open the image, convert it into grayscale and blur it to get rid of the noise.
+    @snippet samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp setup
+-# Create a window with header "Source" and display the source file in it.
+    @snippet samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp createWindow
+-# Create a trackbar on the source_window and assign a callback function to it
+   In general callback functions are used to react to some kind of signal, in our
+   case it's trackbar's state change.
+   @snippet samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp taskbar
+-# Explicit one-time call of `thresh_callback` is necessary to display
+   the "Contours" window simultaniously with the "Source" window.
+   @snippet samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp callback00
+-# Wait for user to close the windows.
+   @snippet samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp waitForIt
+
+
+The callback function `thresh_callback` does all the interesting job.
+
+
+-# Writes to `threshold_output` the threshold of the grayscale picture (you can check out about thresholding @ref tutorial_threshold "here").
+   @snippet samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp threshold
+-# Finds contours and saves them to the vectors `contour` and `hierarchy`.
+    @snippet samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp findContours
+-# For every found contour we now apply approximation to polygons
+   with accuracy +-3 and stating that the curve must me closed.
+
+   After that we find a bounding rect for every polygon and save it to `boundRect`.
+
+   At last we find a minimum enclosing circle for every polygon and
+   save it to `center` and `radius` vectors.
+   @snippet samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp allthework
+
+We found everything we need, all we have to do is to draw.
+
+-# Create new Mat of unsigned 8-bit chars, filled with zeros.
+   It will contain all the drawings we are going to make (rects and circles).
+   @snippet samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp zeroMat
+-# For every contour: pick a random color, draw the contour, the bounding rectangle and
+   the minimal enclosing circle with it,
+   @snippet samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp forContour
+-# Display the results: create a new window "Contours" and show everything we added to drawings on it.
+   @snippet samples/cpp/tutorial_code/ShapeDescriptors/generalContours_demo1.cpp showDrawings
+
 Result
 ------