Computer Science 1033A/B Lecture Notes - Lecture 5: Gif, Human Eye, Hash Table

• School: Western University
• Department: Computer Science
• Course: Computer Science 1033A/B
• Professor: Laura Reid

Document Summary

Reduce redundancy of image data as much as possible for faster download speeds. Compress as much as possible without sacrificing quality (losing bits info) 1024 bytes = 1 kb, 1024 kb = 1 mb. 5760000/1024 = 5,625 kb /1024 = 5. 5 mb. Every time you do a file > save. Compresses down the exact image, detail and quality is preserved. Compresses original bits and bytes into less bits and bytes. No loss (all info is still there) Gif - lzw compression: reduces file sizes by finding repeated patterns of pixels: ex. 123451234512345, 1 reps pattern 12345, can compress to 111: if same numbers but diff order (ex. 0 = 12345, 3 = 43521 etc. Every time you do a file > save for web and devices. Discards selected portions (that are least missed or noticed) of the image. Cannot get info back once its discarded. Jpeg: human eye detects changes in brightness before colour.