c++ - OpenCV waitKey() 函数在 mac 上总是返回 255

Question

1. 我在 Mac(版本 10.12.2)上测试了 OpenCV waitKey() 函数，但它 < b>似乎没有正常工作。无论是否按下任何键，它总是返回 255!我想知道它是安装不正确 还是 OpenCV 本身的错误。任何修复它的想法将不胜感激。

2. 这是我的程序的源代码:

   #include "opencv2/highgui/highgui.hpp"
   #include <iostream>
   
   int main() {
       int ch;
       cv::namedWindow("Test waitKey()", cv::WINDOW_AUTOSIZE);
       cv::Mat image = cv::Mat(100,100,CV_8U, cv::Scalar(0));
       cv::imshow("Test waitKey()", image);
   
       for (;;){
           ch = cv::waitKey(1000);
           std::cout << ch << std::endl;  // always return 255
   
           // and this if statement will never be executed!
           if (ch == 'q')    break;
       }
   
       return 0;
   }
   

3. 这里是 cv::getBuildInformation() 函数的输出:

   General configuration for OpenCV 3.2.0 
   =====================================
   Version control:               unknown
   
   Platform:
   Timestamp:                   2017-01-14T14:50:25Z
   Host:                        Darwin 16.3.0 x86_64
   CMake:                       3.7.2
   CMake generator:             Unix Makefiles
   CMake build tool:            /usr/bin/make
   Configuration:               RELEASE
   
   C/C++:
   Built as dynamic libs?:      YES
   C++ Compiler:                /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++  (ver 8.0.0.8000042)
   C++ flags (Release):         -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -fdiagnostics-show-option -Wno-long-long -Qunused-arguments -Wno-semicolon-before-method-body -fno-omit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -fvisibility=hidden -fvisibility-inlines-hidden -O3 -DNDEBUG  -DNDEBUG
   C++ flags (Debug):           -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -fdiagnostics-show-option -Wno-long-long -Qunused-arguments -Wno-semicolon-before-method-body -fno-omit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -fvisibility=hidden -fvisibility-inlines-hidden -g  -O0 -DDEBUG -D_DEBUG
   C Compiler:                  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
   C flags (Release):           -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -fdiagnostics-show-option -Wno-long-long -Qunused-arguments -Wno-semicolon-before-method-body -fno-omit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -fvisibility=hidden -fvisibility-inlines-hidden -O3 -DNDEBUG  -DNDEBUG
   C flags (Debug):             -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor -Wno-unnamed-type-template-args -Wno-comment -fdiagnostics-show-option -Wno-long-long -Qunused-arguments -Wno-semicolon-before-method-body -fno-omit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -fvisibility=hidden -fvisibility-inlines-hidden -g  -O0 -DDEBUG -D_DEBUG
   Linker flags (Release):
   Linker flags (Debug):
   ccache:                      NO
   Precompiled headers:         NO
   Extra dependencies:          -framework OpenCL -framework Cocoa -framework AVFoundation -framework CoreGraphics -framework CoreMedia -framework CoreVideo -framework QuartzCore -framework Accelerate
   3rdparty dependencies:       libjpeg libwebp libpng libtiff libjasper IlmImf zlib
   
   OpenCV modules:
   To be built:                 core flann imgproc ml photo video imgcodecs shape videoio highgui objdetect superres ts features2d calib3d stitching videostab python2
   Disabled:                    world
   Disabled by dependency:      -
   Unavailable:                 cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev java python3 viz
   
   GUI: 
   QT:                          NO
   Cocoa:                       YES
   OpenGL support:              NO
   VTK support:                 NO
   
   Media I/O: 
   ZLib:                        build (ver 1.2.8)
   JPEG:                        build (ver 90)
   WEBP:                        build (ver 0.3.1)
   PNG:                         build (ver 1.6.24)
   TIFF:                        build (ver 42 - 4.0.2)
   JPEG 2000:                   build (ver 1.900.1)
   OpenEXR:                     build (ver 1.7.1)
   GDAL:                        NO
   GDCM:                        NO
   
   Video I/O:
   DC1394 1.x:                  NO
   DC1394 2.x:                  NO
   FFMPEG:                      NO
     avcodec:                   NO
     avformat:                  NO
     avutil:                    NO
     swscale:                   NO
     avresample:                NO
   GStreamer:                   NO
   OpenNI:                      NO
   OpenNI PrimeSensor Modules:  NO
   OpenNI2:                     NO
   PvAPI:                       NO
   GigEVisionSDK:               NO
   Aravis SDK:                  NO
   AVFoundation:                YES
   V4L/V4L2:                    NO/NO
   XIMEA:                       NO
   gPhoto2:                     NO
   
   Parallel framework:            GCD
   
   Other third-party libraries:
   Use IPP:                     9.0.1 [9.0.1]
        at:                     /Users/ngoclinhng/opencv/release/3rdparty/ippicv/ippicv_osx
   Use IPP Async:               NO
   Use VA:                      NO
   Use Intel VA-API/OpenCL:     NO
   Use Lapack:                  YES (-framework Accelerate)
   Use Eigen:                   NO
   Use Cuda:                    NO
   Use OpenCL:                  YES
   Use OpenVX:                  NO
   Use custom HAL:              NO
   
   OpenCL:                        <Link with OpenCL library>
   Link libraries:              -framework OpenCL
   Use AMDFFT:                  NO
   Use AMDBLAS:                 NO
   
   Python 2:
   Interpreter:                 /usr/bin/python2.7 (ver 2.7.10)
   Libraries:                   /usr/lib/libpython2.7.dylib (ver 2.7.10)
   numpy:                       /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/numpy/core/include (ver 1.8.0rc1)
   packages path:               lib/python2.7/site-packages
   
   Python 3:
   Interpreter:                 /Users/ngoclinhng/anaconda/bin/python3 (ver 3.5.2)
   
   Python (for build):            /usr/bin/python2.7
   
   Java:
   ant:                         NO
   JNI:                         /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk/System/Library/Frameworks/JavaVM.framework/Headers /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk/System/Library/Frameworks/JavaVM.framework/Headers /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk/System/Library/Frameworks/JavaVM.framework/Headers
   Java wrappers:               NO
   Java tests:                  NO
   
   Matlab:                        Matlab not found or implicitly disabled
   
   Documentation:
   Doxygen:                     NO
   
   Tests and samples:
   Tests:                       YES
   Performance tests:           YES
   C/C++ Examples:              NO
   
   Install path:                  /usr/local
   
   cvconfig.h is in:              /Users/ngoclinhng/opencv/release
   -----------------------------------------------------------------
   

Answer 1

你应该改用cvWaitKey(n)~ 在 OpenCV 3.1 之后，当在 n 毫秒内没有按键按下时，cv::waitKey(n) 的返回值从 -1 变为 255。