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Data compression
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Compression makes files smaller so they take less space and travel faster across networks. The trick is choosing what, if anything, to throw away.
Why compress?
Smaller files use less storage, download and upload faster, and use less bandwidth.
Streaming video and music would be very hard without compression.
Streaming video and music would be very hard without compression.
Lossless compression
The file is made smaller without losing any data. The original can be rebuilt exactly.
Essential for text, program files and spreadsheets, where every bit matters. Examples: ZIP, PNG.
Essential for text, program files and spreadsheets, where every bit matters. Examples: ZIP, PNG.
Lossy compression
Some data is permanently removed, usually detail people will hardly notice.
Files become much smaller, but the original cannot be restored.
Used for photos, music and video. Examples: JPEG and MP3.
Files become much smaller, but the original cannot be restored.
Used for photos, music and video. Examples: JPEG and MP3.
A school wants to email a 60-page report and a holiday photo. Which type of compression suits each?
- Report: every character matters, so lossless.
- Photo: small loss of detail is fine, so lossy gives a much smaller file.
Answer: Lossless for the report, lossy for the photo
Compression saves storage and transmission time. Lossless keeps all the data and can be reversed exactly. Lossy permanently removes some data to make much smaller files (JPEG, MP3).
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