我检查了很多关于LZW压缩的来源，但它没有使用图像文件。
以下是我目前检查过的资源：
https://www.codemiles.com/java/lzw-data-compression-decompression-algorithm-java-code-t99.html
这个压缩文件比原始文件大
https://codereview.stackexchange.com/questions/122080/simplifying-lzw-compression-decompression
您能否提供任何与图像压缩相关的资源？ 感谢!!!
答案 0 :(得分：0)
Compressing an already compressed image is not a good idea, because the first compression removes any statistical hints the second compressor can use. That's at least true for contemporary compression algorithms, like they are used in the JPEG, PNG, GIF, TIFF, and WebP image formats. Typically, a compressed file, viewed in a hex editor, looks quite like a stream of random bytes, and random data (or non-random data with statistical properties similar to random data) cannot be compressed. Usually the result is even bigger than the original, due to some overhead in the storage format. Clever compressors detect this condition and revert to simply storing the original data, rather than compressing it.
So if you think that your image might be compressed further, you'll have to decompress it first. Then you can try a different compressor that might yield better results. However, I doubt that any LZW variant will give you any significant gain over JPEG. While it's a really clever enhancement of the Lempel-Ziv family of compression algorithms, LZW is a purely lossless technique, and hence has some innate limitation of the attainable compression ratio, rooted in the statistical distribution of the image data. JPEG and other lossy image formats trade image quality for size, and thus can easily outperform lossless techniques.
Note that the GIF format is a special case. While it uses lossless LZW compression, it requires a color palette of up to 256 entries. To encode a colorful image like a photograph as GIF, you'll have to quantize the color space first to get a 256-color palette. This is once again a lossy technique, albeit quite different from the algorithms used by JPEG and WebP lossy. Quantized GIF images of photos compress excellently due to the reduction of RGB information in the image, but expose noticeable deteriorations of color gradients, like they are found in human faces, flower leaves, and a cloudy heaven.
As an aside: If GIF would allow larger color palettes (say, 1024), it might become a real killer format for photographic images. Maybe it's time for a GIF17a format update?!