无损是什么？- 概念解释

无损压缩，简单定义

无损压缩是一种减小文件大小的方法，允许从压缩数据中完美恢复原始数据。压缩过程中不会丢失任何信息。

无损压缩就像速记符号。与其写「AAAAAAAAAA」（10 个 A），你可以写「10xA」，信息相同，字符更少。解压时，你会得到完全相同的原始「AAAAAAAAAA」。

无损算法查找数据中的模式和冗余，并用更紧凑的表示方式替换它们。ZIP 使用 DEFLATE，PNG 使用过滤器 + DEFLATE，FLAC 使用线性预测编码，解压后都能产生相同的输出。

无损压缩对于任何需要完美准确性的数据至关重要：文档、代码、电子表格、可执行文件，以及任何单个比特改变都会导致损坏或错误的数据。

ZIP losslessly compresses documents and files. Unzipping always produces identical copies of the original files.

PNG uses lossless compression for images. A PNG image edited and saved 1000 times is identical to the original.

FLAC losslessly compresses audio. Decoding FLAC produces bit-perfect audio identical to the original recording.

Microsoft Office formats use ZIP compression internally. All data is perfectly preserved.

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常见问题

Lossless: no data lost, perfect reconstruction, larger files. Lossy: data permanently discarded, smaller files, slight quality reduction.

Yes, PNG is always lossless. Every pixel is perfectly preserved when saving as PNG, unlike JPEG.

Yes, ZIP is always lossless. Files inside a ZIP archive are exactly identical to the originals when extracted.

For archiving or editing: use lossless (PNG or TIFF). For web sharing: JPEG or WebP lossy is fine as they look almost identical at good settings.

FLAC is the most popular lossless audio format. WAV and AIFF are also lossless but larger. Apple ALAC is Apple's lossless format.