Introduction

OpenCV itself can show a bitmap using imshow() function but in a wxWidgets application one may want to display a bitmap acquired with OpenCV using wxWidgets GUI. The most convenient class for doing that in wxWidgets is wxBitmap.

Project wxOpenCVTest presents function

bool ConvertMatBitmapTowxBitmap(const cv::Mat& matBitmap, wxBitmap& bitmap);

which converts an OpenCV bitmap encoded as BGR CV_8UC3 (the most common format) to a wxBitmap.

The function comes with a simple program which uses OpenCV and wxWidgets to acquire and display bitmaps coming from several sources: image file, video file, default webcam, and IP camera. The program also benchmarks how long a bitmap took to acquire, convert, and display. The program can be built using a provided CMakeFile.

Tested on MS Windows 10 only, with wxWidgets 3.1.5 and OpenCV 4.4 using MSVC (64-bit, MSVS 2017 and 2019) and GCC (32-bit, mingw-w64-i686-toolchain with GCC 10.2).

Please read the comments in convertmattowxbmp.h, they contain useful and perhaps surprising information (e.g., how much slower the debug version of the generic convert function is on MSW).

How to use

1. Add files convertmattowxbmp.h and convertmattowxbmp.cpp to your project.
2. Include convertmattowxbmp.h where needed.
3. Call ConvertMatBitmapTowxBitmap() as described in the comments in convertmattowxbmp.h.

Notes

After closing a debug build of a wxWidgets application linking to OpenCV DLL (via import library opencv_world440d.lib), MSVS reports many memory leaks, even in the simplest possible application just declaring a cv::Mat variable without ever touching it or calling any OpenCV function. No such leaks are there for pure Win32 application equivalent. I found similar reports on the internet, but no conclusive solution or even explanation.

Surprisingly, OpenCV does not really support Unicode paths, see for example opencv/opencv#4292 (comment) for more information.

Licence

wxWidgets licence