Reduce the size of an image.

identify name1.file name2.file  #.... (This will give the details of files.)
convert in.file -resize n out.file # (converts infile to outfile of size n x n+dn )

Reverse the order of rows

sed -n '1!G;h;$p' file1 > file2

Copying n1 and n2 columns from data file 'file1' and writing in to a newly created file 'file2'

  

 awk '{print $n1  "\t"   $n2}' file1 > file2