Raspberry pi-OpenCV Modify image tutorial - Raspberry Pi Forums

hello,

trying tutorial learn how pass arguments inside code, supposed convert existing image grayscale , save it. here link: http://docs.opencv.org/2.4/doc/tutorial ... save-image

here code (i compiled same thing):

#include <cv.h>
#include <highgui.h>

using namespace cv;

int main( int argc, char** argv )
{
char* imagename = argv[1];

mat image;
image = imread( imagename, 1 );

if( argc != 2 || !image.data )
{
printf( " no image data \n " );
return -1;
}

mat gray_image;
cvtcolor( image, gray_image, cv_bgr2gray );

imwrite( "../../images/gray_image.jpg", gray_image );

namedwindow( imagename, cv_window_autosize );
namedwindow( "gray image", cv_window_autosize );

imshow( imagename, image );
imshow( "gray image", gray_image );

waitkey(0);

return 0;
}
error:
terminate called after throwing instance of 'std::logic_error"
(): basic_string::_s_contruct not null valid
aborted


searched error , people suggest checking argc (int) number before starting code. checked it, argc 1. supposed 2 call argv[1]. how can handle situation? need convert existing image grayscale , save it.

yes, badly written program. code should check argc 2, before using argv[1]. however, guessing comment aren't passing name of image file program on command line.

need run program follows

code: select all

./a.out filename.jpg

filename.jpg existing image file. if file isn't in current directory need provide path file. also, replace a.out name of executable creating.

code have been better written as:-

code: select all

#include <cv.h> #include <highgui.h>  using namespace cv;  int main( int argc, char** argv ) {  if( argc != 2 || !image.data )  {    printf( "usage %s input.jpg\n ", argv[0] );    return -1;  }   char* imagename = argv[1];   mat image;  image = imread( imagename, 1 );   mat gray_image;  cvtcolor( image, gray_image, cv_bgr2gray );   imwrite( "gray_image.jpg", gray_image );   namedwindow( imagename, cv_window_autosize );  namedwindow( "gray image", cv_window_autosize );   imshow( imagename, image );  imshow( "gray image", gray_image );   waitkey(0);   return 0; }

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