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Google 的 Guetzli,對 JPEG 的壓縮演算法

Google Research Europe 推出的演算法,在不動 decoder 的情況下,要怎麼樣壓出又小又清晰的 JPEG 圖片:「Announcing Guetzli: A New Open Source JPEG Encoder」,論文可以在「Guetzli: Perceptually Guided JPEG Encoder」這邊下載,程式碼則可以在 GitHub 上的 google/guetzli 取得。

othree 也寫了一篇「Guetzli: A New Open Source JPEG Encoder」介紹 Guetzli。

Guetzli 在同樣的品質下,比現有的壓縮法可以再壓榨出 29%~45% 的空間,這算是非常驚人的數字:

We reach a 29-45% reduction in data size for a given perceptual distance, according to Butteraugli, in comparison to other compressors we tried.

但代價是需要極為大量的 CPU resource 計算,這使得他沒辦法用在太動態的環境裡:

Guetzli's computation is currently extremely slow, which limits its applicability to compressing static content and serving as a proof- of-concept that we can achieve significant reductions in size by combining advanced psychovisual models with lossy compression techniques.

但只要是在批次處理產生的過程 (不需要太在意要等很久),都可以考慮用這個工具...