ImageMagick

A list of examples:

• Two slices of a picture that is 1000px wide with 10% overlap
  • Left: convert -quality 100% -crop 60%x100% big.jpg left.jpg
  • Right: convert -quality 100% -crop 60%x100%+Wx100% big.jpg right.jpg
  • if H = height, then W = original_width - 1.5 * H
• Scale
  • convert in.jpg -resize 50% out.jpg
• Montage Grid
  • montage *.JPG -geometry WxH+HSpace+VSpace montage.jpg
    • WxH is the width and height of a given tile (use the minimum of all your tiles) and HSpace and VSpace are the number of pixels between each tile. You can use the -tile flag to describe the grid you want.