Harvard Extension School
CSCI E-12 Fundamentals of Web Site Development | Fall 2019

## Compression for Indexed GIF

GIF LZW compression operates on horizontal blocks of the same color. Here are two images that are identical except for a 90 degree rotation. The vertical stripe GIF image is nearly twice as large as the horizontal stripe GIF image. The PNG images are the same size.

Format | Horizontal Stripes | Vertical Stripes
--- | --- | ---
GIF | 471 bytes | 911 bytes
PNG | 232 bytes | 221 bytes

Copyright © David Heitmeyer