OpenCV expected constructor, desctructor or type conversion

When I compile the code below I get the following errors:

./main.cpp:150: error: expected constructor, destructor, or type conversion before ‘(’ token <br>
../main.cpp:154: error: expected constructor, destructor, or type conversion before ‘(’ token
../main.cpp:156: error: expected constructor, destructor, or type conversion before ‘(’ token
../main.cpp:158: error: expected constructor, destructor, or type conversion before ‘(’ token <br>

But the code looks okay. He has problems with


The program:

#include "iostream"
#include "stdlib.h"
#include "stdio.h"
#include "cv.h"
#include "highgui.h"
#include "cstring"/*the includes*/

/*You may change the values of the sthreshold and hlower and hupper to get different results....*/
const int sthreshold=210;
const double hlower=178;
const double hupper=3;

/*Note:The detection algorithm is the same as the one you can find in one of my previous posts

The same algorithm is copied from that post and pasted in this
post only the values of the "sthreshold" and the "hupper" and the "hlower" are different....*/

int main()

int i,j,k;//for iterations
int height,width,step,channels;/*HSV means the frame after color conversion*/
int heightmono,widthmono,stepmono,channelsmono;/*mono means the frame which has the monochrome image*/
const char string1[]="monoimg.avi";/*This is the name of the video which would be the outcome of the blob detection program..*/

uchar *data,*datamono;


IplImage *frame = 0;

int key = 0;/*Initializing the capture from the video...*/

CvCapture* capture = cvCreateFileCapture( "partofvideo3.avi" );

double fps = cvGetCaptureProperty (/*getting the capture properties......the frame rate..*/

CvSize size = cvSize(

(int)cvGetCaptureProperty( capture, CV_CAP_PROP_FRAME_WIDTH),

(int)cvGetCaptureProperty( capture, CV_CAP_PROP_FRAME_HEIGHT)


CvVideoWriter* writer=cvCreateVideoWriter(string1, CV_FOURCC( 'D','I','V','X'),fps,size) ;

/* always check */

if (!capture) {

fprintf (stderr, "Cannot open video file!\n");



height = frame->height;

width = frame->width;

step = frame->widthStep;

channels = frame->nChannels;

data = (uchar *)frame->imageData;

/* create a window for the video,one for the monochrome image and the other for the original frame */

cvNamedWindow("monoimage", CV_WINDOW_AUTOSIZE);

cvNamedWindow("original frame", CV_WINDOW_AUTOSIZE);

for (;;) {/*keep looping till we are out of frames...*/

if (!cvGrabFrame(capture)) {



/*colimgbot---means color image of the bot*/

frame = cvRetrieveFrame(capture);

IplImage *colimgbot = cvCreateImage( cvGetSize(frame), 8, 3 );

IplImage *monoimgbot = cvCreateImage( cvGetSize(frame), 8, 1 );


cvCvtColor(frame,frame,CV_RGB2HSV);/*Converting the color space of the Video....*/

/*I have explained this loop in the previous program....*/

for(i=0;i< (height);i++)
if((data[(height-i)*step+j*channels]<=hlower) && (data[(height-i)*step+j*channels]>=hupper))
/*"height-i" because if we use only "i" we were getting vertically inverted result...hence reinverting the same
would do the required....*/

else datamono[i*stepmono+j*channelsmono]=0;

/*Please check these links for the explanation of the erosion and dilation functions*/

/*so now the last parameter in the function indicates how many times you want to apply dilation
or erosion*/

cvDilate( monoimgbot,monoimgbot,0,15);

/*here i have experimented with the values by changing them...and i have found

that i come to a good result by applying erosion 14 times and dilation 15 times
you can comment/uncomment play with the values and see what is going on
Sometimes you will find the areas which are shining in the image also get detected...

Please think why and then try to post a comment the best commment would get visible on this page*/

cvWriteFrame(writer, monoimgbot);/*Write the monochrome video to the writer..

to save the results of the video extract*/

cvShowImage("original frame", frame);

cvShowImage("monoimage", monoimgbot);

if( (cvWaitKey(10) & 255) == 27 ) break;



/* free memory */


//cvDestroyWindow("original frame");





If you'd indent your code, it would probably help you find problems like this. Keeping main (or any other single function) to a halfway reasonable length would probably help too. From the looks of things, this code:


//cvDestroyWindow("original frame");




...(at the end of what you posted) is all outside of any function. Code like this has to be inside a function.

Posted on by Jerry Coffin

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