JPG vs PNG

For Distributed Proofreaders projects, use

• .png files for:
  • proofing images (page scans)
  • engravings
  • line drawings
  • monochrome images

• .jpg files for:
  • continuous-tone images
  • paintings
  • photographs

• either .jpg or .png, whichever yields the better-quality image, for:
  • grayscale illustrations