c++ dynamic allocation with opencv exception - c++

Question

i have the following code. i used it after applying connected components code i have the wanted results from connected components but i'm trying using the following code to remove the very small or very high labels based on a threshold.but every time i debug it i have exception.. so could anybode help me please
this is the connected components code
#include <stdio.h>
#include <math.h>
#include <cv.h>
#include <highgui.h>
#define PIXEL(img,x,y) (img)->imageData[(x)*img->widthStep+(y)]
#include <iostream>
int main()
{
IplImage *GrayImg,*outImg;
GrayImg=cvLoadImage("Gray_Image.jpg",0);
if(!GrayImg){
printf("Could not load image file: %s\n");
cvWaitKey(0);
exit(0);
}
cvThreshold(GrayImg, GrayImg, 180, 255, CV_THRESH_BINARY | CV_THRESH_OTSU);//converting image to binary
int height,width,channels;
height = GrayImg->height;
width = GrayImg->width;
channels = GrayImg->nChannels;
printf("Processing a %dx%d image with %d channels \n",height,width,channels);
outImg = cvCreateImage(cvSize(width, height), IPL_DEPTH_8U, 1);
cvZero(outImg);
//cvCopyImage(GrayImg,OutImg);
int i,j,v;
int top,left;
int topL,leftL;
int label=0;
int eq[10000][2];
int eqlength = 1;
cvNamedWindow("Gray", CV_WINDOW_AUTOSIZE);
cvShowImage("Gray", GrayImg );
for (i=0;i<height;i++) {
for (j=0;j<width;j++) {
v = (unsigned char) PIXEL(GrayImg,i,j);// cvGet2D(GrayImg,i,j).val[0];
//unsigned char v1 = PIXEL(GrayImg,i,j);
//int v2 = PIXEL(GrayImg,i,j);
//int v3 = v1;
if (v==255) {
if (i>0) top = cvGet2D(GrayImg,i-1,j).val[0];
else top = 0;
if (j>0) left = cvGet2D(GrayImg,i,j-1).val[0] ;
else left=0;
if (top==0 && left==0)
{
PIXEL(outImg,i,j) = label;
label+=1;
}
else if (top==255 && left==0) {
PIXEL(outImg,i,j) = PIXEL(outImg,i-1,j);
}
else if (top==0 && left==255) {
PIXEL(outImg,i,j) = PIXEL(outImg,i,j-1);
}
else if (top==255 && left==255) {
PIXEL(outImg,i,j) = PIXEL(outImg,i,j-1);
if (PIXEL(outImg,i-1,j) != PIXEL(outImg,i,j-1)){
if (eq[eqlength-1][0] == PIXEL(outImg,i-1,j) && eq[eqlength-1][1] == PIXEL(outImg,i,j-1)) ;
else
{
eq[eqlength][0] = PIXEL(outImg,i-1,j);
eq[eqlength][1] = PIXEL(outImg,i,j-1);
eqlength++;
}
}
}
}
}
//cvWaitKey(0);
//cvShowImage("Out", outImg);
}
int e;
for (i=0;i<height;i++)
for (j=0;j<width;j++)
if (PIXEL(outImg,i,j)!=0)
for (e=1;e<eqlength;e++)
if (PIXEL(outImg,i,j)==eq[e][0])
PIXEL(outImg,i,j)=eq[e][1];
cvNamedWindow("Out", CV_WINDOW_AUTOSIZE);
cvShowImage("Out", outImg);
and this is the code i added to remove unwanted labels
int* arr = new int [N];
//cout<<endl<<arr[0];
for (i=0;i<height;i++)
{
for (j=0;j<width;j++)
{
id=(unsigned char)PIXEL(outImg,i,j);
arr[id]++;
}
}
for (i=0;i<=N;i++)
{
if (arr[i]<5 || arr[i]>50)
arr[i]=0;
}
for (i=0;i<outImg->height;i++)
{
for (j=0;j<outImg->width;j++)
{
id=(unsigned char)PIXEL(outImg,i,j);
//id=cvGet2D(outImg,i,j).val[0];
if (arr[id]==0)
PIXEL(outImg,i,j)=0;
else
PIXEL(outImg,i,j)=255;
}
}
delete [] arr;
cvNamedWindow("CC", CV_WINDOW_AUTOSIZE);
cvShowImage("CC", outImg);
cvWaitKey(0);
/* Free memory and get out */
cvDestroyWindow("Gray");
cvReleaseImage(&GrayImg);
return 0;
}

Answer 1

You are exceeding the bounds of your array arr. Indexes are 0 based in C++ so when allocating an array of size N your maximum index is N-1.
int* arr = new int [N];
...
for (i=0;i<=N;i++) // Accessing element N of arr which does not exist. Use '<'
{
if (arr[i]<5 || arr[i]>50)
arr[i]=0;
}