Thread: Edge Detect

How would i use the convolution kernel

Code:

int 
{1,1,1
 1,-8,1
 1,1,1}

to edge detect an image? I have all the neccessary functions to open the image, and set the image into an array, with array elements being the corresponding pixel values. How can i edge detect? I know kernel relates to a set of pixels in the array, with -8 corresponding to teh centre pixel. But i do not understand how to normalise the values, or how i am to get the edge detected value. Thanks for your help.