# PhotoshopElements

# Understanding file compression

Many image file formats compress image data to reduce file size. Lossless compression preserves all image data without removing detail; lossy compression removes image data and loses some detail.

The following are commonly used compression techniques:

RLE (Run Length Encoding)
  Lossless compression technique that compresses the transparent portions of each layer in images with multiple layers containing transparency.

LZW (Lemple-Zif-Welch)
  Lossless compression that provides the best results in compressing images that contain large areas of single color.

JPEG
  Lossy compression that provides the best results with photographs.

CCITT
  A family of lossless compression techniques for black-and-white images.

ZIP
  Lossless compression technique that is most effective for images that contain large areas of a single color.

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