RGB image into binary image using OpenCV - c++

Question

So, I'm super noob and I'm trying to do something that convert an RGB image to binary image in C/C++, using OpenCV. My first program was this:
#include <opencv.hpp>
using namespace cv;
int main ( int argc, char **argv )
{
Mat im_gray = imread("img1.png",CV_LOAD_IMAGE_GRAYSCALE);
Mat im_rgb = imread("img.png");
Mat im_gray;
cvtColor(im_rgb,im_gray,CV_RGB2GRAY);
Mat img_bw = im_gray > 128;
imwrite("image_bw.jpg", img_bw);
return 0;
}
But it says "There were build errors" and it opens just the original image. How can I do it right? Can anybody help me with this?
The output was:
'opencv.exe': Loaded 'D:\Imagens\pibiti\opencv\Debug\opencv.exe', Symbols loaded.
'opencv.exe': Loaded 'C:\Windows\System32\ntdll.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\kernel32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\KernelBase.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'D:\Imagens\pibiti\opencv\opencv\opencv_core230d.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'D:\Imagens\pibiti\opencv\opencv\opencv_highgui230d.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\msvcp100d.dll', Symbols loaded.
'opencv.exe': Loaded 'C:\Windows\System32\msvcr100d.dll', Symbols loaded.
'opencv.exe': Loaded 'C:\Windows\System32\user32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\gdi32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\ole32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\oleaut32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\advapi32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\WinSxS\x86_microsoft.windows.common-controls_6595b64144ccf1df_5.82.9200.16384_none_bf100cd445f4d954\comctl32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\avifil32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\msvfw32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\avicap32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\combase.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\msvcrt.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\rpcrt4.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\sechost.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\winmm.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\msacm32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\shell32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\version.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\winmmbase.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\shlwapi.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\imm32.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\msctf.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\cryptbase.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\bcryptprimitives.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Windows\System32\uxtheme.dll', Cannot find or open the PDB file
'opencv.exe': Loaded 'C:\Program Files\Iminent\Iminent.WinCore.dll', Binary was not built with debug information.
'opencv.exe': Loaded 'C:\Windows\System32\dwmapi.dll', Cannot find or open the PDB file
The thread 'Win32 Thread' (0xd9c) has exited with code -1073741510 (0xc000013a).
WinCore .dll DLL_PROCESS_DETACH:The program '[4136] opencv.exe: Native' has exited with code -1073741510 (0xc000013a).
PS.: Using Windows 8 + Visual Studio 10 + OpenCV 2.3.
The image I'm trying to convert to binary image: img1.png

Answer 1

#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
//using namespace cv;
int main ( int argc, char **argv )
{
cv::Mat im_gray; // no nead to load the Mat with anything when declaring it.
cv::Mat im_rgb = cv::imread("img.png");
cv::cvtColor(im_rgb, im_gray,CV_RGB2GRAY);
// INSTEAD of the above two lines you could have cv::Mat im_gray = imread("img1.png",CV_LOAD_IMAGE_GRAYSCALE);
// the following is an alternative to Mat img_bw = im_gray > 128
cv::Mat img_bw;
cv::threshold(im_gray, img_bw, 128.0, 255.0, THRESH_BINARY);
cv::imwrite("image_bw.jpg", img_bw);
return 0;
}

Answer 2

remove extra Mat im_gray; and include path is set to OpenCV2.3/build/include and the program compiles.
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
using namespace cv;
int main ( int argc, char **argv )
{
Mat im_gray = imread("img1.png",CV_LOAD_IMAGE_GRAYSCALE);
Mat im_rgb = imread("img.png");
cvtColor(im_rgb,im_gray,CV_RGB2GRAY);
Mat img_bw = im_gray > 128;
imwrite("image_bw.jpg", img_bw);
return 0;
}
edit:
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
using namespace cv;
int main( int argc, char** argv )
{
Mat img = imread( "C:/test/img1.png");
cvtColor(img,img,CV_BGR2GRAY);
Mat left=img(Rect(0,0,300,151));
Mat right=img(Rect(300,0,img.cols-300,151));
threshold(left,left,0,255,CV_THRESH_OTSU);
threshold(right,right,0,255,CV_THRESH_OTSU);
imshow("img",img);
waitKey(0);
return 0;
}