Question

I have started learning OpenCV.
I am working on linux.
From their documentation page I was able to compile this
http://docs.opencv.org/doc/tutorials/introduction/linux_gcc_cmake/linux_gcc_cmake.html#linux-gcc-usage

However after that I got lost in trying to declare a new mat and it’s constructors.
SO I decided to go with this book http://www.amazon.com/Learning-OpenCV-Computer-Vision-Library/dp/0596516134
However I am not able to compile the very first program from this book.
The program is here :

#include "highgui.h"
int main(int argc, char** argv)
{
    IplImage* img = cvLoadImage (argv[1]);
    cvNamedWindow("Example1", CV_WINODW_AUTOSIZE);
    cvShowImage("Example1",img);
    cvWaitKey(0);
    cvReleaseImage(&img);
    cvDestroyWindow("Example1");
}

I saved this in a file named load.c

Then I created a CMakeLists.txt file and put this in it :

project( load )
find_package( OpenCV REQUIRED )
add_executable( load load )
target_link_libraries( load ${OpenCV_LIBS} )

when running “cmake .” from terminal it is succesful. But when I am running “make” it gives me this error :

Scanning dependencies of target load
[100%] Building C object CMakeFiles/load.dir/load.o
/home/ishan/load/load.c: In function ‘main’:
/home/ishan/load/load.c:4:2: error: too few arguments to function ‘cvLoadImage’
/usr/local/include/opencv2/highgui/highgui_c.h:212:18: note: declared here
/home/ishan/load/load.c:5:28: error: ‘CV_WINODW_AUTOSIZE’ undeclared (first use in this  function)
/home/ishan/load/load.c:5:28: note: each undeclared identifier is reported only once for each function it appears in
make[2]: *** [CMakeFiles/load.dir/load.o] Error 1
make[1]: *** [CMakeFiles/load.dir/all] Error 2
make: *** [all] Error 2

I think it is because this example in the book is for OpenCV 1.x while I am currently running 2.4.3, however I believe there must be a way to run this program and the subsequent program that are in the book.
I think the problem lies with linking the header files properly.
I would like to first read from the book and using reference from documentation and then switch to documentation fully. But for now I wish to learn from the book as learning from the book is far easier to me than documentation. Plus I bought this book for approx 3000 INR and got it just today, I don’t want to see it go to waste. I want to learn from it.

Please help me out.

Answer 1

CV_WINODW_AUTOSIZE is mispelled. The correct constant is CV_WINDOW_AUTOSIZE

cvLoadImage (argv[1]); should be cvLoadImage (argv[1], 1); (for loading a color image) because the C standard does not support default arguments.

By the way, if you’re using OpenCV 2.0+, I recommend learning the C++ API. It’s a lot less convoluted than the C API and performance is comparable.