imgshrink can shrink the size of your PET images, a program for shrinking the size of a dynamic or static PET image to take less memory and disk space, and to reduce computation time when testing pixel-by-pixel modeling methods.ECAT 6.3, 7.x and Analyze 7.5 formats are accepted.
Eight neighbouring pixels are averaged into one pixel; thus image size will be shrunk into 1/8 of the size of the original image.
These are the command line arguments:
1. PET image file
2. Shrunk image file

Options:
-z=<Yes|no>
Nr of image planes (z dimension) is halved (default) or not changed
-h or --help
Print this message and exit
--version or --build
Print software build information and exit
--silent
Program works silently, printing only error and warning messages

The license of this software is Freeware, you can free download and free use this image optimizer software.