Hi i need to convert an image to b&w with C. I'm on MXLinux. And my idea is to use opencv api. I search on web and i found this way to gain b&w foto. The problem is only when i try to compile it with gcc. It can't found the library opencv, how i can link (permanently not only local) this library?
#include <string.h>
#include <cv.h>
#include <highgui.h>
int main(int argc, char** argv){
//read and convert to greyscale
IplImage* im_rgb = cvLoadImage("home.jpg");
IplImage* im_gray = cvCreateImage(cvGetSize(im_rgb),IPL_DEPTH_8U,1);
cvCvtColor(im_rgb,im_gray,CV_RGB2GRAY);
//to black and white
IplImage* im_bw = cvCreateImage(cvGetSize(im_gray),IPL_DEPTH_8U,1);
cvThreshold(im_gray,im_bw,128,255,CV_THRESH_BINARY | CV_THRESH_OTSU);
//save the image
cvSaveImage("image_bw.png",im_bw);
cvSaveImage("image_grey.png",im_gray);
}
The other question is, why doesn't gcc see automatically the library ? After the installation i see the /usr/local/bin and the library are on it!
-----UPDATE1----- 25-02-2021 -----
Yes, after OpenCV 3.x library C seems doesn't exist or maybe doesn't work. Problem solved by install OpenCV 3.4.3.
Compile in this way: gcc NameFile.cpp -o NameFile $ ( pkg-config --cflags --libs opencv )
I obtain an error (i think is caused by cvSaveImage) :
what(): OpenCV(3.4.3) /home/pi/opencv-3.4.3/modules/core/src/matrix_wrap.cpp: 800: error: (-215:Assertion failed) (flags & FIXED_TYPE) != 0 in function 'type'
--SOLVED--
I solved all problem by installing an other version of OpenCV, via web i found that the 3.4.3 version has a bug with matrix_wrap i really don't understand very well the problem but with a clean installation of opencv 3.0.0 all works fine. I get only few error on cmake and make but all are easy to resolve by web.
Thanks to all.
