Merge branch 4.x

Author: alalek

.github/ISSUE_TEMPLATE.md

@@ -1,3 +1,10 @@
+<!--
+If you have a question rather than reporting a bug please go to https://forum.opencv.org where you get much faster responses.
+If you need further assistance please read [How To Contribute](https://github.com/opencv/opencv/wiki/How_to_contribute).
+
+This is a template helping you to create an issue which can be processed as quickly as possible. This is the bug reporting section for the OpenCV library.
+-->
+
 ##### System information (version)
 <!-- Example
 - OpenCV => 4.2
@@ -26,26 +33,25 @@
 
  - [ ] I report the issue, it's not a question
    <!--
-   OpenCV team works with answers.opencv.org, Stack Overflow and other communities
-   to discuss problems. Tickets with question without real issue statement will be
+   OpenCV team works with forum.opencv.org, Stack Overflow and other communities
+   to discuss problems. Tickets with questions without a real issue statement will be
    closed.
    -->
  - [ ] I checked the problem with documentation, FAQ, open issues,
-       answers.opencv.org, Stack Overflow, etc and have not found solution
+       forum.opencv.org, Stack Overflow, etc and have not found any solution
    <!--
    Places to check:
    * OpenCV documentation: https://docs.opencv.org
    * FAQ page: https://github.com/opencv/opencv/wiki/FAQ
-   * OpenCV forum: https://answers.opencv.org
+   * OpenCV forum: https://forum.opencv.org
    * OpenCV issue tracker: https://github.com/opencv/opencv/issues?q=is%3Aissue
-   * OpenCV Contrib issue tracker: https://github.com/opencv/opencv_contrib/issues?q=is%3Aissue
    * Stack Overflow branch: https://stackoverflow.com/questions/tagged/opencv
    -->
- - [ ] I updated to latest OpenCV version and the issue is still there
+ - [ ] I updated to the latest OpenCV version and the issue is still there
    <!--
    master branch for OpenCV 4.x and 3.4 branch for OpenCV 3.x releases.
-   OpenCV team supports only latest release for each branch.
-   The ticket is closed, if the problem is not reproduced with modern version.
+   OpenCV team supports only the latest release for each branch.
+   The ticket is closed if the problem is not reproduced with the modern version.
    -->
  - [ ] There is reproducer code and related data files: videos, images, onnx, etc
    <!--
@@ -55,9 +61,9 @@
      to reduce attachment size
    * Use PNG for images, if you report some CV related bug, but not image reader
      issue
-   * Attach the image as archive to the ticket, if you report some reader issue.
+   * Attach the image as an archive to the ticket, if you report some reader issue.
      Image hosting services compress images and it breaks the repro code.
-   * Provide ONNX file for some public model or ONNX file with with random weights,
+   * Provide ONNX file for some public model or ONNX file with random weights,
      if you report ONNX parsing or handling issue. Architecture details diagram
      from netron tool can be very useful too. See https://lutzroeder.github.io/netron/
    -->

.github/PULL_REQUEST_TEMPLATE.md

@@ -3,9 +3,9 @@
 See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
 
 - [ ] I agree to contribute to the project under Apache 2 License.
-- [ ] To the best of my knowledge, the proposed patch is not based on a code under GPL or other license that is incompatible with OpenCV
-- [ ] The PR is proposed to proper branch
-- [ ] There is reference to original bug report and related work
+- [ ] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
+- [ ] The PR is proposed to the proper branch
+- [ ] There is a reference to the original bug report and related work
 - [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
       Patch to opencv_extra has the same branch name.
 - [ ] The feature is well documented and sample code can be built with the project CMake

README.md

@@ -2,7 +2,7 @@
 
 This repository is intended for the development of so-called "extra" modules,
 contributed functionality. New modules quite often do not have stable API,
-and they are not well-tested. Thus, they shouldn't be released as a part of
+and they are not well-tested. Thus, they shouldn't be released as a part of the
 official OpenCV distribution, since the library maintains binary compatibility,
 and tries to provide decent performance and stability.
 
@@ -33,7 +33,7 @@ $ cmake -DOPENCV_EXTRA_MODULES_PATH=<opencv_contrib>/modules -DBUILD_opencv_lega
 
 If you also want to build the samples from the "samples" folder of each module, also include the "-DBUILD_EXAMPLES=ON" option.
 
-If you prefer using the gui version of cmake (cmake-gui), then, you can add `opencv_contrib` modules within `opencv` core by doing the following:
+If you prefer using the GUI version of CMake (cmake-gui), then, you can add `opencv_contrib` modules within `opencv` core by doing the following:
 
 1. Start cmake-gui.
 
@@ -55,6 +55,6 @@ If you prefer using the gui version of cmake (cmake-gui), then, you can add `ope
 
 In order to keep a clean overview containing all contributed modules, the following files need to be created/adapted:
 
-1. Update the README.md file under the modules folder. Here, you add your model with a single line description.
+1. Update the README.md file under the modules folder. Here, you add your model with a single-line description.
 
-2. Add a README.md inside your own module folder. This README explains which functionality (separate functions) is available, links to the corresponding samples and explains in somewhat more detail what the module is expected to do. If any extra requirements are needed to build the module without problems, add them here also.
+2. Add a README.md inside your own module folder. This README explains which functionality (separate functions) is available, links to the corresponding samples, and explains in somewhat more detail what the module is expected to do. If any extra requirements are needed to build the module without problems, add them here also.

modules/aruco/include/opencv2/aruco.hpp

@@ -146,6 +146,24 @@ enum CornerRefineMethod{
  *   Parameter is the standard deviation in pixels.  Very noisy images benefit from non-zero values (e.g. 0.8). (default 0.0)
  * - detectInvertedMarker: to check if there is a white marker. In order to generate a "white" marker just
  *   invert a normal marker by using a tilde, ~markerImage. (default false)
+ * - useAruco3Detection: to enable the new and faster Aruco detection strategy. The most important observation from the authors of
+ *   Romero-Ramirez et al: Speeded up detection of squared fiducial markers (2018) is, that the binary
+ *   code of a marker can be reliably detected if the canonical image (that is used to extract the binary code)
+ *   has a size of minSideLengthCanonicalImg (in practice tau_c=16-32 pixels).
+ *   Link to article: https://www.researchgate.net/publication/325787310_Speeded_Up_Detection_of_Squared_Fiducial_Markers
+ *   In addition, very small markers are barely useful for pose estimation and thus a we can define a minimum marker size that we
+ *   still want to be able to detect (e.g. 50x50 pixel).
+ *   To decouple this from the initial image size they propose to resize the input image
+ *   to (I_w_r, I_h_r) = (tau_c / tau_dot_i) * (I_w, I_h), with tau_dot_i = tau_c + max(I_w,I_h) * tau_i.
+ *   Here tau_i (parameter: minMarkerLengthRatioOriginalImg) is a ratio in the range [0,1].
+ *   If we set this to 0, the smallest marker we can detect
+ *   has a side length of tau_c. If we set it to 1 the marker would fill the entire image.
+ *   For a FullHD video a good value to start with is 0.1.
+ * - minSideLengthCanonicalImg: minimum side length of a marker in the canonical image.
+ *   Latter is the binarized image in which contours are searched.
+ *   So all contours with a size smaller than minSideLengthCanonicalImg*minSideLengthCanonicalImg will omitted from the search.
+ * - minMarkerLengthRatioOriginalImg:  range [0,1], eq (2) from paper
+ *   The parameter tau_i has a direct influence on the processing speed.
  */
 struct CV_EXPORTS_W DetectorParameters {
 
@@ -188,6 +206,12 @@ struct CV_EXPORTS_W DetectorParameters {
 
     // to detect white (inverted) markers
     CV_PROP_RW bool detectInvertedMarker;
+
+    // New Aruco functionality proposed in the paper:
+    // Romero-Ramirez et al: Speeded up detection of squared fiducial markers (2018)
+    CV_PROP_RW bool useAruco3Detection;
+    CV_PROP_RW int minSideLengthCanonicalImg;
+    CV_PROP_RW float minMarkerLengthRatioOriginalImg;
 };