Hacker News 上看到「Compressing Text into Images (shkspr.mobi)」這個奇怪的方法，是把文字轉成灰階的 PNG 檔案，然後跟 ZIP 比較壓縮率，居然是能打的。原文則是在「Compressing Text into Images」這邊。

這是屬於週末奇怪的 side project，作者也覺得這樣很白爛 XDDD

(This is, I think, a silly idea. But sometimes the silliest things lead to unexpected results.)

作者是拿羅密歐與茱麗葉的小說當資料 (Romeo and Juliet)，這可以在 Project Gutenberg 的網站上下載到 txt 檔案。

基本的想法是把每個文字轉成灰階圖片的像素，然後用 PNG 無損輸出，最後再用 Squoosh 處理：

The English language and its punctuation are not very complicated, so the play only contains 77 unique symbols. The ASCII value of each character spans from 0 - 127. So let's create a greyscale image which each pixel has the same greyness as the ASCII value of the character.

結果居然是跟一般的壓縮軟體差不多：

That's down to 55KB! About 40% of the size of the original file. It is slightly smaller than ZIP, and about 9 bytes larger than Brotli compression.

我試著驗證作者的想法，用 Go 寫了個小程式輸出操作圖片，產稱一張寬度是小說的 byte 數，高度只有 1 的 PNG 檔輸出，最後再用 pngcrush 處理：「gslin/text-to-image-compression」。

另外我是與 gzip 比較 (原作者是與 ZIP 比較)，結果是：

PNG: 64379
Gzip: 64563
Gzip (-9): 64331

的確是差不多的等級？

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