http://en.wikipedia.org/wiki/Template_matching

template_matching.java

minSAD = VALUE_MAX;
 
// loop through the search image
for ( int x = 0; x <= S_rows - T_rows; x++ ) {
    for ( int y = 0; y <= S_cols - T_cols; y++ ) {
        SAD = 0.0;
 
        // loop through the template image
        for ( int i = 0; i < T_rows; i++ )
            for ( int j = 0; j < T_cols; j++ ) {
 
                pixel p_SearchIMG = S[x+i][y+j];
 
                pixel p_TemplateIMG = T[i][j];
 
                SAD += abs( p_SearchIMG.Grey - p_TemplateIMG.Grey );
            }
    }
 
    // save the best found position 
    if ( minSAD > SAD ) {
        minSAD = SAD;
        // give me VALUE_MAX
        position.bestRow = x;
        position.bestCol = y;
        position.bestSAD = SAD;
    }
}