ViSP中识别AprilTag的C++实例代码与运行结果

VISP中识别AprilTag的C++可运行代码与运行结果

Introduction

***具体解释见下一篇：***VISP中识别AprilTag的C++实例代码解释
***具体帮助开发文档下载：***开发文档

This tutorial shows how to detect one or more AprilTag marker with ViSP. To this end, we provide vpDetectorAprilTag class that is a wrapper over Apriltag 3rd party library. Notice that there is no need to install this 3rd party, since AprilTag source code is embedded in ViSP.
用VISP的话就不用下载AprilTag官方的.c和.cpp文件，VISP中的函数已经集成好了AprilTag的识别定位函数

The vpDetectorAprilTag class inherits from vpDetectorBase class, a generic class dedicated to detection. For each detected tag, it allows retrieving some characteristics such as the tag id, and in the image, the polygon that contains the tag and corresponds to its 4 corner coordinates, the bounding box and the center of gravity of the tag.
具体vpDetectorAprilTag类下载开发文档可以看，里面有集成好的识别和定位函数

Moreover, vpDetectorAprilTag class allows estimating the 3D pose of the tag. To this end, the camera parameters as well as the size of the tag are required.
这个vpDetectorAprilTag类也可以用于识别3D场景下的tag

In the next sections you will find examples that show how to detect tags in a single image or in images acquired from a camera connected to your computer.
下面这一节是一个例子，识别一张电脑中图片中的tag

Note that all the material (source code and image) described in this tutorial is part of ViSP source code and could be downloaded using the following command:
下面的下载地址可以下载源码和图片

$ svn export https://github.com/lagadic/visp.git/trunk/tutorial/detection/tag

也可以自己利用OpenMV生成AprilTag，比较清晰
参考另一篇：OpenMV生成AprilTag码

Print an AprilTag marker

官方介绍的是UNIX系统中打印的方法，其实下载好了之后自己编辑一下用打印机打印就行。

AprilTag detection and pose estimation (single image)

#include <visp3/detection/vpDetectorAprilTag.h>
#include <visp3/gui/vpDisplayGDI.h>
#include <visp3/gui/vpDisplayOpenCV.h>
#include <visp3/gui/vpDisplayX.h>
#include <visp3/io/vpImageIo.h>
#include <visp3/core/vpXmlParserCamera.h>int main(int argc, const char **argv)
{
#if defined(VISP_HAVE_APRILTAG) && (defined(VISP_HAVE_X11) || defined(VISP_HAVE_GDI) || defined(VISP_HAVE_OPENCV))std::string input_filename = "AprilTag.pgm";vpDetectorAprilTag::vpAprilTagFamily tagFamily = vpDetectorAprilTag::TAG_36h11;vpDetectorAprilTag::vpPoseEstimationMethod poseEstimationMethod = vpDetectorAprilTag::HOMOGRAPHY_VIRTUAL_VS;double tagSize = 0.053;float quad_decimate = 1.0;int nThreads = 1;std::string intrinsic_file = "";std::string camera_name = "";bool display_tag = false;int color_id = -1;unsigned int thickness = 2;bool z_aligned = false;for (int i = 1; i < argc; i++) {if (std::string(argv[i]) == "--pose_method" && i + 1 < argc) {poseEstimationMethod = (vpDetectorAprilTag::vpPoseEstimationMethod)atoi(argv[i + 1]);} else if (std::string(argv[i]) == "--tag_size" && i + 1 < argc) {tagSize = atof(argv[i + 1]);} else if (std::string(argv[i]) == "--input" && i + 1 < argc) {input_filename = std::string(argv[i + 1]);} else if (std::string(argv[i]) == "--quad_decimate" && i + 1 < argc) {quad_decimate = (float)atof(argv[i + 1]);} else if (std::string(argv[i]) == "--nthreads" && i + 1 < argc) {nThreads = atoi(argv[i + 1]);} else if (std::string(argv[i]) == "--intrinsic" && i + 1 < argc) {intrinsic_file = std::string(argv[i + 1]);} else if (std::string(argv[i]) == "--camera_name" && i + 1 < argc) {camera_name = std::string(argv[i + 1]);} else if (std::string(argv[i]) == "--display_tag") {display_tag = true;} else if (std::string(argv[i]) == "--color" && i + 1 < argc) {color_id = atoi(argv[i + 1]);} else if (std::string(argv[i]) == "--thickness" && i + 1 < argc) {thickness = (unsigned int)atoi(argv[i + 1]);} else if (std::string(argv[i]) == "--tag_family" && i + 1 < argc) {tagFamily = (vpDetectorAprilTag::vpAprilTagFamily)atoi(argv[i + 1]);} else if (std::string(argv[i]) == "--z_aligned") {z_aligned = true;} else if (std::string(argv[i]) == "--help" || std::string(argv[i]) == "-h") {std::cout << "Usage: " << argv[0]<< " [--input <input file>] [--tag_size <tag_size in m>]"" [--quad_decimate <quad_decimate>] [--nthreads <nb>]"" [--intrinsic <intrinsic file>] [--camera_name <camera name>]"" [--pose_method <method> (0: HOMOGRAPHY, 1: HOMOGRAPHY_VIRTUAL_VS, "" 2: DEMENTHON_VIRTUAL_VS, 3: LAGRANGE_VIRTUAL_VS, "" 4: BEST_RESIDUAL_VIRTUAL_VS, 5: HOMOGRAPHY_ORTHOGONAL_ITERATION) (default: 0)]"" [--tag_family <family> (0: TAG_36h11, 1: TAG_36h10 (DEPRECATED), 2: TAG_36ARTOOLKIT (DEPRECATED),"" 3: TAG_25h9, 4: TAG_25h7 (DEPRECATED), 5: TAG_16h5, 6: TAG_CIRCLE21h7, 7: TAG_CIRCLE49h12,"" 8: TAG_CUSTOM48h12, 9: TAG_STANDARD41h12, 10: TAG_STANDARD52h13) (default: 0)]"" [--display_tag] [--color <color_id (0, 1, ...)>]"" [--thickness <thickness>] [--z_aligned]"" [--help]"<< std::endl;return EXIT_SUCCESS;}}vpCameraParameters cam;cam.initPersProjWithoutDistortion(615.1674805, 615.1675415, 312.1889954, 243.4373779);vpXmlParserCamera parser;if (!intrinsic_file.empty() && !camera_name.empty())parser.parse(cam, intrinsic_file, camera_name, vpCameraParameters::perspectiveProjWithoutDistortion);std::cout << cam << std::endl;std::cout << "poseEstimationMethod: " << poseEstimationMethod << std::endl;std::cout << "tagFamily: " << tagFamily << std::endl;std::cout << "nThreads : " << nThreads << std::endl;std::cout << "Z aligned: " << z_aligned << std::endl;try {vpImage<unsigned char> I;vpImageIo::read(I, input_filename);#ifdef VISP_HAVE_X11vpDisplayX d(I);
#elif defined(VISP_HAVE_GDI)vpDisplayGDI d(I);
#elif defined(VISP_HAVE_OPENCV)vpDisplayOpenCV d(I);
#endifvpDetectorAprilTag detector(tagFamily);detector.setAprilTagQuadDecimate(quad_decimate);detector.setAprilTagPoseEstimationMethod(poseEstimationMethod);detector.setAprilTagNbThreads(nThreads);detector.setDisplayTag(display_tag, color_id < 0 ? vpColor::none : vpColor::getColor(color_id), thickness);detector.setZAlignedWithCameraAxis(z_aligned);vpDisplay::display(I);double t = vpTime::measureTimeMs();std::vector<vpHomogeneousMatrix> cMo_vec;detector.detect(I, tagSize, cam, cMo_vec);t = vpTime::measureTimeMs() - t;std::stringstream ss;ss << "Detection time: " << t << " ms for " << detector.getNbObjects() << " tags";vpDisplay::displayText(I, 40, 20, ss.str(), vpColor::red);for (size_t i = 0; i < detector.getNbObjects(); i++) {std::vector<vpImagePoint> p = detector.getPolygon(i);vpRect bbox = detector.getBBox(i);vpDisplay::displayRectangle(I, bbox, vpColor::green);std::string message = detector.getMessage(i);std::size_t tag_id_pos = message.find("id: ");if (tag_id_pos != std::string::npos) {int tag_id = atoi(message.substr(tag_id_pos + 4).c_str());ss.str("");ss << "Tag id: " << tag_id;vpDisplay::displayText(I, (int)(bbox.getTop() - 10), (int)bbox.getLeft(), ss.str(), vpColor::red);}for (size_t j = 0; j < p.size(); j++) {vpDisplay::displayCross(I, p[j], 14, vpColor::red, 3);std::ostringstream number;number << j;vpDisplay::displayText(I, p[j] + vpImagePoint(15, 5), number.str(), vpColor::blue);}}vpDisplay::displayText(I, 20, 20, "Click to display tag poses", vpColor::red);vpDisplay::flush(I);vpDisplay::getClick(I);vpDisplay::display(I);for (size_t i = 0; i < cMo_vec.size(); i++) {vpDisplay::displayFrame(I, cMo_vec[i], cam, tagSize / 2, vpColor::none, 3);}vpDisplay::displayText(I, 20, 20, "Click to quit.", vpColor::red);vpDisplay::flush(I);vpDisplay::getClick(I);} catch (const vpException &e) {std::cerr << "Catch an exception: " << e.getMessage() << std::endl;}return EXIT_SUCCESS;
#else(void)argc;(void)argv;return 0;
#endif
}

The default behavior is to detect 36h11 marker in AprilTag.pgm image, but –tag_family option allows considering other tags. To see which are the options, just run:

$ ./tutorial-apriltag-detector --help

To detect multiple 36h11 tags in the AprilTag.pgm image that is provided just run:

$ ./tutorial-apriltag-detector

结果：

点击一下图片：