Slightly OT: Transpose a matrix in C

[agabriel at home.tzo.org (Anthony Gabrielson)]

Hello,
	Sorry this is OT...  I'm trying to transpose a 2D matrix in C and 
its being a bit tough.  My code works great for squares but everything 
else failes.  Here is the function:

uint8 * imageTranspose( uint8 *im ){
    uint8   *im_transpose;
    int     x, y, org_offset, tran_offset;
    //dims[0] is X length and dims[1] is Y length. dims is global
    int		im_size  = dims[0] * dims[1];

    if ( (im_transpose = malloc(sizeof(uint16) * im_size)) == NULL )
        mexErrMsgTxt("trans im malloc failed...\n");
    
    //Transpose
    for(x=0;x<dims[0]; x++){
        for(y=0;y<dims[1]; y++){
            org_offset = x+(y*dims[0]); //So X=X & Y=Y
            tran_offset= y-(x*dims[1]); //So X=Y & Y=X
            *(im_transpose+tran_offset) = *(im+org_offset); 
            
//mexPrintf("%d\t%d\n",*(im+org_offset),*(im_transpose+tran_offset));
        }
    }
    
    return im_transpose;
}

So this function works well with square arrays but doesn't work with non 
square arrays.  I'm not sure why and I can't find any reference on the 
web.  Any help would be appreciated.

Thanks,
Anthony