可逆 vs 非可逆 画像圧縮—完全技術ガイド 2026
新着2026-02-012分で読めます1ツール
可逆と非可逆の画像圧縮の違いを理解。用途に合った形式を選ぶ。
What is Lossless Compression?
Lossless compression preserves all image data without any quality loss. PNG and GIF use this type. Ideal for logos, icons, and screenshots.
What is Lossy Compression?
Lossy compression discards invisible data to reduce file size. JPG and WebP use it. Ideal for photographs—the loss is barely noticeable at high quality.
When to Use Each Type
Lossless: logos, screenshots, sharp graphics. Lossy: personal photos, product images, website photos.
Why Are PNG Files So Large?
PNG uses lossless compression—it keeps every pixel. Complex photographs produce huge PNG files. Converting to JPG reduces size by 70–80%.
Frequently Asked Questions
- What is the difference between PNG and JPG?
- PNG is lossless and supports transparency. JPG is lossy, smaller, and does not support transparency.
- Which format is best for logos?
- PNG for logos—it preserves sharp edges and transparency.