Question

Well this is a layman’s attempt on blurring an image, i am not using any specific [already known] alogrithm, i am implementing my own technique.

float k[][5]= { .01, .01, .01, .01, .01,
                .01, .01, .01,  .01, .01,
                .01, .01, .01,  .01, .01};

for( row = 0; row < rows; ++row) 
    {
            sum=0;
            for ( col = 0; col < cols; ++col) 
            {               
                            temp_ptr  = &((uchar*)(img->imageData + (img->widthStep*row)))[col];
                            for( i=1; i<6;i++)
                            {
                                float factor=exp((float)(-(i-col)*(i-col)/(2*sigma2))); 
                                sum+=factor;
                                for( j=1; j<6 ;j++)
                                {
                                    if( (row-j)>0 && (col-i)>0   )
                                    k[i-1][j-1]+=factor*temp_ptr[row-i+col-j];
                                }
                                for( j=1; j<6 ;j++)
                                {
                                    if( (row-j)>0 && (col-i)>0   )
                                    {
                                    uchar* temp_ptr1  = &((uchar*)(img->imageData + (img->widthStep * (row-1) )))[col-1];

                                temp_ptr1[0]=temp_ptr[0]*k[i-1][j-1]/sum;   
                                temp_ptr1[1]=temp_ptr[1]*k[i-1][j-1]/sum;   
                                temp_ptr1[2]=temp_ptr[2]*k[i-1][j-1]/sum;   
                                    }
                                }
                            }
            }
    }

Answer 1

Your j index is out of bound for array k.
It can not be greater than 5 !

In 5th for you should change upper bound to 5 not 6.