Image search

I'm trying to implement the image search described here
http://www.dspguide.com/ch24/6.htm. I have to check for existence of a
target image. Upon convolution we will have some values, each value
proportional to the match.  There may one or more maximas depending on
repetition of the target. so is the case If target does not exist in
the source image.Although in the latter case, values will be far lower
in magnitude.
Yet, how could one conclusively say if target does exist in the
source?

>Yet, how could one conclusively say if target does exist in the
>source?


You can't.  As the peak becomes higher above the noise, it is less likely
that the peak is just a random result of the noise.  That is, as the peak
becomes higher, the probability of the target being present approaches
100%, but never exactly becomes 100%.  You simply have to set an arbitray
threshold for a yes/no answer.
Regards,
Steve