VLIB function IMG_conv_3x3_i8_c8s on 6748

Hi,
we just started using some VLIB  functions for one of our codes on C6748, but we have some problems with the way they behave.

I want to use the function to process picture, picture's size is  256*256 ,but I always get the bad result.

My reslut and code as follow:

SIZE: the size of mask is 3.

HEIGHT and WIDTH is the picture's size.

for(i=0; i<SIZE*SIZE; i++)
 {
   mask[i] = 1;
 }
 for(j=0; j<HEIGHT-2; j++)
 {
  IMG_conv_3x3_i8_c8s(&Gray[WIDTH*j], &BLURGREYimage[WIDTH*(j+1)+1], WIDTH-2,WIDTH, &mask[0], 3);
 }

Input :

Output:

Could you help me?

Best regard!