How Image Compression Works
Understand lossy and lossless compression, quality controls, dimensions, and why exact file sizes require iteration.
The short answer
Lossless compression rewrites image data more efficiently without changing decoded pixels. Lossy compression removes details that are less noticeable to human vision. The quality control changes how aggressively an encoder simplifies that information.
A quality-first workflow
File size cannot be predicted perfectly from quality alone because every image contains different detail. Exact-target tools test encodes, usually with binary search, and may reduce dimensions when quality reduction is no longer a good trade.
Why this matters
Image dimensions, file size, format, and compression settings all affect upload success, page speed, and visible quality. The right workflow starts with the actual requirement, then changes only what is needed.
About the author
PixelPerfect publishes browser-based image optimization tools and practical guides about image compression, image resizing, JPG, PNG, WebP, dimensions, and file-size limits.
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