3 ms·

While "needed" to produce "nice" (acceptable) looking 4-level images, it's likely breaking the filtering and compression steps of PNG format compression, making

• lelanthran 5y ago
  Would using GIF help? Then a 4-level image would use only a single byte for each pixel, and the entire file can be compressed if necessary. For example, here is the comparison of the first image on their page (file sizes in bytes), converted to gif with 4-level: 25700 sps_close.gif 43415 sps_close.png [EDIT] Interestingly enough, converting their image to a 7-level (1 for alpha) gif image gives you double the colors while reducing the image size by 17,715 bytes (~17.2kB)
  • ReactiveJelly 5y ago
    In the general case you aren't going to beat a lossy compression specialized for photos (JPEG) with a lossless compression trying to compress something you've added noise to (PNG / GIF) when trying to compress a photo
    • lelanthran 5y ago
      What does the general case have to do with it? At the target visual quality I doubt that jpg offers any size saving over a gif.