cv::imwrite could not find a writer for the specified extension

Question

The following command causes an exception.

cv::imwrite(\"test.jpg\", diffImg);

I also tried numerous variations on this, including absolute

Answer 1

You need to recompile OpenCV and add support to "jpeg" format. Get the lastest opencv code and run cmake:

svn co http://code.opencv.org/svn/opencv/trunk/opencv myopencvdir.svn/
cd myopencvdir.svn/
mkdir release
cd release/
cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local ..

And check if libjpeg, libpng, libtiff are supported. If not you need to install them and re-run cmake.

Example of cmake output that shows Media I/O support:

--   Media I/O: 
--     ZLib:                       TRUE
--     JPEG:                       TRUE
--     PNG:                        TRUE
--     TIFF:                       TRUE
--     JPEG 2000:                  TRUE
--     OpenEXR:                    YES