Compact build for OpenCV applications on Windows - c++

Question

I was reading this article on how to create compact builds for applications using OpenCV.
But, this article includes only GCC related optimizations. I am looking for equivalent options in Visual Studio, but am able to find only the option to minimize size (/Os) and the option /LTCG.
I am building a very simple OpenCV console application (code is below) using OpenCV static libraries built from source. The issue is the size of executable is too large (37 MB in Debug build and 19 MB in Release build). I want to reduce that size to a few MBs and I am looking for ways to do that - I found that article while researching about this.
#include <iostream>
#include <opencv2/core.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/imgcodecs.hpp>
int main()
{
cv::Mat m = cv::imread("sample.jpg");
cv::imwrite("output.jpg", m);
std::cout << "Hello World!\n" << m.rows << " " << m.cols;
return 0;
}
Just in case anyone wants to know, I am including following libraries (the below are for Release mode):
opencv_core430.lib
opencv_imgproc430.lib
opencv_imgcodecs430.lib
libjpeg-turbo.lib
libpng.lib
libtiff.lib
libwebp.lib
ippiw.lib
zlib.lib
IlmImf.lib
libjasper.lib
ittnotify.lib
ippicvmt.lib
If anyone has any ideas what equivalent options are in Visual Studio, it would be of great help.
Also, is there anyone who was successful to reduce the executable size using static OpenCV libraries on Visual Studio?

Answer 1

I encountered the same issue and I found two things which make a big difference: performance libraries/frameworks and unnecessary file types.
Since you are building from source, you should be able to use cmake-gui to adjust the configuration to disable these:
WITH_IPP
WITH_ITT
WITH_OPENCL
Then, disable these additional image types if you need only JPG:
WITH_JASPER
WITH_PNG
WITH_OPENJPEG
WITH_WEBP
WITH_TIFF
WITH_OPENEXR
WITH_IMGCODEC_HDR
WITH_IMGCODEC_SUNRASTER
WITH_IMGCODEC_PXM
WITH_IMGCODEC_PFM
Since imread and imwrite determine the file type based on the given string, the linker has no way of knowing that the code for the other unnecessary image formats can be removed.
When I apply these changes and compile your program using Visual Studio 2022 it comes out to about 1.7 MB in release mode. (Starting with the default configuration and disabling only BUILD_SHARED_LIBS, I had seen the same 19 MB executable that you had reported.)

Answer 2

You can build as per your modules requirements, details in the blog.
The simplest way to build is using OpenCV cmake example:
cmake
-D WITH_CUDA=OFF \
-D WITH_MATLAB=OFF \
-D BUILD_ANDROID_EXAMPLES=OFF \
-D BUILD_DOCS=OFF \
-D BUILD_PERF_TESTS=OFF \
-D BUILD_TESTS=OFF \
-D BUILD_SHARED_LIBS=OFF \
-D BUILD_opencv_objdetect=OFF \
-D BUILD_opencv_video=OFF \
-D BUILD_opencv_videoio=OFF \
-D BUILD_opencv_features2d=OFF \
-D BUILD_opencv_flann=OFF \
-D BUILD_opencv_ml=OFF \
-D BUILD_opencv_photo=OFF \
-D BUILD_opencv_python=OFF \
-D BUILD_opencv_shape=OFF \
-D BUILD_opencv_stitching=OFF \
-D BUILD_opencv_superres=OFF \
-D BUILD_opencv_ts=OFF \
-D BUILD_opencv_videostab=OFF \
-D BUILD_opencv_highgui=ON \
-D BUILD_opencv_imgproc=ON \
..
For static linking, you can pick and choice the module(s) by un-archiving .a to .o and bundle them in single .a.
CAUTION: be very sure that you do not break the dependencies.
Example:
to unarchive a .a using ar -x libopencv_imgproc.a and to archive again
ar -rc libopencv_custom.a *.o