why cvCopy wouldn't copy whole of my imageData?

Question

I contact a problem in my opencv poroject that the cvCopy function don't have normal behavior ! so I write this code to test it.

int n = 6;
IplImage* img = cvCreateImage( cvSize(n,n) ,1 ,1 );
uchar* ptr = (uchar*)(img->imageData);

for(int i = 0 ; i< n*n ; i++)
{
    ptr[i] = i+1;
}

std::cout << "befor copy" << std::endl;
for( int i =0 ; i < n*n ;i++)   //print the imageData of img
{
    if ( i % n == 0 )
        std::cout<<std::endl;
    std::cout << std::setw(4) <<(int) ptr[i];
}

IplImage* img2 = cvCreateImage(cvGetSize(img),img->depth,img->nChannels);
cvCopy(img,img2);

ptr = (uchar*)(img2->imageData);
std::cout << "\nafter copy" << std::endl;
for( int i =0 ; i < n*n ;i++)    //print the imageData of img2
{
    if ( i % n == 0 )
        std::cout<<std::endl;
    std::cout << std::setw(4) <<(int) ptr[i];
}
std::cout<<std::endl;

but the output is :

befor copy

 1   2   3   4   5   6    
 7   8   9  10  11  12
13  14  15  16  17  18
19  20  21  22  23  24
25  26  27  28  29  30
31  32  33  34  35  36
after copy

 1   2   3   4   5   6
 7   8   9  10  11  12
13  14  15  16  17  18
19  20  21  22  23  24
25  26   0   0   0   0
 0   0   0   0   0   0

So, it just copied until the number 26; not all the imageData !
why cvCopy behaves like this ?

Answer 1

The probem is with:

IplImage* img = cvCreateImage( cvSize(n,n) ,1 ,1 );

You have set the depth to 1 , but it should be something like IPL_DEPTH_8U. Here depth=1 does not mean 1 byte, it is depth in bits. You would be best to use one of the predefined values . Eg

IplImage* img = cvCreateImage(cvSize(n, n), IPL_DEPTH_8U, 1);